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System/Random.hs:43:1: warning: [-Wtabs] #55

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p-alik opened this issue Aug 28, 2019 · 1 comment
Closed

System/Random.hs:43:1: warning: [-Wtabs] #55

p-alik opened this issue Aug 28, 2019 · 1 comment
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@p-alik
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p-alik commented Aug 28, 2019

stack build with lts-13.26 warns

random              >
random              > /tmp/stack5350/random-1.1/System/Random.hs:43:1: warning: [-Wtabs]
random              >     Tab character found here, and in 74 further locations.
random              >     Please use spaces instead.
random              >    |
random              > 43 |         (
random              >    | ^^^^^^^^

@nagaflokhu mentioned it also in #50

There are also warnings about tab characters further up cabal's message.

random/System/Random.hs

Lines 42 to 43 in cfdfe6f

module System.Random
(

curiousleo added a commit to curiousleo/random that referenced this issue May 26, 2020
author Alexey Kuleshevich <[email protected]> 1581472095 +0300
committer Leonhard Markert <[email protected]> 1590493894 +0200

This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

MonadRandom
-----------

This patch adds a class 'MonadRandom':

    -- | 'MonadRandom' is an interface to monadic pseudo-random number generators.
    class Monad m => MonadRandom g s m | g m -> s where
      {-# MINIMAL freezeGen,thawGen,(uniformWord32|uniformWord64) #-}

      type Frozen g = (f :: Type) | f -> g
      freezeGen :: g s -> m (Frozen g)
      thawGen :: Frozen g -> m (g s)

      uniformWord32 :: g s -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g s -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

Conceptually, in 'MonadRandom g s m', 'g s' is the type of the
generator, 's' is the state type, and 'm' the underlying monad. Via the
functional dependency 'g m -> s', the state type is determined by the
generator and monad.

'Frozen' is the type of the generator's state "at rest". It is defined
as an injective type family via 'f -> g', so there is no ambiguity as to
which 'g' any 'Frozen g' belongs to.

This definition is generic enough to accommodate, for example, the 'Gen'
type from the 'mwc-random' package, which itself abstracts over the
underlying primitive monad and state token. The documentation shows the
full 'MonadRandom Gen' instance.

Four 'MonadRandom' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
curiousleo added a commit to curiousleo/random that referenced this issue May 26, 2020
author Alexey Kuleshevich <[email protected]> 1581472095 +0300
committer Leonhard Markert <[email protected]> 1590493894 +0200

This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

MonadRandom
-----------

This patch adds a class 'MonadRandom':

    -- | 'MonadRandom' is an interface to monadic pseudo-random number generators.
    class Monad m => MonadRandom g s m | g m -> s where
      {-# MINIMAL freezeGen,thawGen,(uniformWord32|uniformWord64) #-}

      type Frozen g = (f :: Type) | f -> g
      freezeGen :: g s -> m (Frozen g)
      thawGen :: Frozen g -> m (g s)

      uniformWord32 :: g s -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g s -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

Conceptually, in 'MonadRandom g s m', 'g s' is the type of the
generator, 's' is the state type, and 'm' the underlying monad. Via the
functional dependency 'g m -> s', the state type is determined by the
generator and monad.

'Frozen' is the type of the generator's state "at rest". It is defined
as an injective type family via 'f -> g', so there is no ambiguity as to
which 'g' any 'Frozen g' belongs to.

This definition is generic enough to accommodate, for example, the 'Gen'
type from the 'mwc-random' package, which itself abstracts over the
underlying primitive monad and state token. The documentation shows the
full 'MonadRandom Gen' instance.

Four 'MonadRandom' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
curiousleo added a commit to curiousleo/random that referenced this issue May 26, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

MonadRandom
-----------

This patch adds a class 'MonadRandom':

    -- | 'MonadRandom' is an interface to monadic pseudo-random number generators.
    class Monad m => MonadRandom g s m | g m -> s where
      {-# MINIMAL freezeGen,thawGen,(uniformWord32|uniformWord64) #-}

      type Frozen g = (f :: Type) | f -> g
      freezeGen :: g s -> m (Frozen g)
      thawGen :: Frozen g -> m (g s)

      uniformWord32 :: g s -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g s -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

Conceptually, in 'MonadRandom g s m', 'g s' is the type of the
generator, 's' is the state type, and 'm' the underlying monad. Via the
functional dependency 'g m -> s', the state type is determined by the
generator and monad.

'Frozen' is the type of the generator's state "at rest". It is defined
as an injective type family via 'f -> g', so there is no ambiguity as to
which 'g' any 'Frozen g' belongs to.

This definition is generic enough to accommodate, for example, the 'Gen'
type from the 'mwc-random' package, which itself abstracts over the
underlying primitive monad and state token. The documentation shows the
full 'MonadRandom Gen' instance.

Four 'MonadRandom' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
lehins added a commit to idontgetoutmuch/random that referenced this issue May 27, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

MonadRandom
-----------

This patch adds a class 'MonadRandom':

    -- | 'MonadRandom' is an interface to monadic pseudo-random number generators.
    class Monad m => MonadRandom g s m | g m -> s where
      {-# MINIMAL freezeGen,thawGen,(uniformWord32|uniformWord64) #-}

      type Frozen g = (f :: Type) | f -> g
      freezeGen :: g s -> m (Frozen g)
      thawGen :: Frozen g -> m (g s)

      uniformWord32 :: g s -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g s -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

Conceptually, in 'MonadRandom g s m', 'g s' is the type of the
generator, 's' is the state type, and 'm' the underlying monad. Via the
functional dependency 'g m -> s', the state type is determined by the
generator and monad.

'Frozen' is the type of the generator's state "at rest". It is defined
as an injective type family via 'f -> g', so there is no ambiguity as to
which 'g' any 'Frozen g' belongs to.

This definition is generic enough to accommodate, for example, the 'Gen'
type from the 'mwc-random' package, which itself abstracts over the
underlying primitive monad and state token. The documentation shows the
full 'MonadRandom Gen' instance.

Four 'MonadRandom' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
lehins added a commit to idontgetoutmuch/random that referenced this issue May 27, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

MonadRandom
-----------

This patch adds a class 'MonadRandom':

    -- | 'MonadRandom' is an interface to monadic pseudo-random number generators.
    class Monad m => MonadRandom g s m | g m -> s where
      {-# MINIMAL freezeGen,thawGen,(uniformWord32|uniformWord64) #-}

      type Frozen g = (f :: Type) | f -> g
      freezeGen :: g s -> m (Frozen g)
      thawGen :: Frozen g -> m (g s)

      uniformWord32 :: g s -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g s -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

Conceptually, in 'MonadRandom g s m', 'g s' is the type of the
generator, 's' is the state type, and 'm' the underlying monad. Via the
functional dependency 'g m -> s', the state type is determined by the
generator and monad.

'Frozen' is the type of the generator's state "at rest". It is defined
as an injective type family via 'f -> g', so there is no ambiguity as to
which 'g' any 'Frozen g' belongs to.

This definition is generic enough to accommodate, for example, the 'Gen'
type from the 'mwc-random' package, which itself abstracts over the
underlying primitive monad and state token. The documentation shows the
full 'MonadRandom Gen' instance.

Four 'MonadRandom' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
lehins added a commit to idontgetoutmuch/random that referenced this issue May 27, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

MonadRandom
-----------

This patch adds a class 'MonadRandom':

    -- | 'MonadRandom' is an interface to monadic pseudo-random number generators.
    class Monad m => MonadRandom g s m | g m -> s where
      {-# MINIMAL freezeGen,thawGen,(uniformWord32|uniformWord64) #-}

      type Frozen g = (f :: Type) | f -> g
      freezeGen :: g s -> m (Frozen g)
      thawGen :: Frozen g -> m (g s)

      uniformWord32 :: g s -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g s -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

Conceptually, in 'MonadRandom g s m', 'g s' is the type of the
generator, 's' is the state type, and 'm' the underlying monad. Via the
functional dependency 'g m -> s', the state type is determined by the
generator and monad.

'Frozen' is the type of the generator's state "at rest". It is defined
as an injective type family via 'f -> g', so there is no ambiguity as to
which 'g' any 'Frozen g' belongs to.

This definition is generic enough to accommodate, for example, the 'Gen'
type from the 'mwc-random' package, which itself abstracts over the
underlying primitive monad and state token. The documentation shows the
full 'MonadRandom Gen' instance.

Four 'MonadRandom' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
@lehins lehins mentioned this issue Jun 4, 2020
curiousleo added a commit to curiousleo/random that referenced this issue Jun 15, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

MonadRandom
-----------

This patch adds a class 'MonadRandom':

    -- | 'MonadRandom' is an interface to monadic pseudo-random number generators.
    class Monad m => MonadRandom g s m | g m -> s where
      {-# MINIMAL freezeGen,thawGen,(uniformWord32|uniformWord64) #-}

      type Frozen g = (f :: Type) | f -> g
      freezeGen :: g s -> m (Frozen g)
      thawGen :: Frozen g -> m (g s)

      uniformWord32 :: g s -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g s -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

Conceptually, in 'MonadRandom g s m', 'g s' is the type of the
generator, 's' is the state type, and 'm' the underlying monad. Via the
functional dependency 'g m -> s', the state type is determined by the
generator and monad.

'Frozen' is the type of the generator's state "at rest". It is defined
as an injective type family via 'f -> g', so there is no ambiguity as to
which 'g' any 'Frozen g' belongs to.

This definition is generic enough to accommodate, for example, the 'Gen'
type from the 'mwc-random' package, which itself abstracts over the
underlying primitive monad and state token. The documentation shows the
full 'MonadRandom Gen' instance.

Four 'MonadRandom' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
curiousleo added a commit to idontgetoutmuch/random that referenced this issue Jun 15, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

MonadRandom
-----------

This patch adds a class 'MonadRandom':

    -- | 'MonadRandom' is an interface to monadic pseudo-random number generators.
    class Monad m => MonadRandom g s m | g m -> s where
      {-# MINIMAL freezeGen,thawGen,(uniformWord32|uniformWord64) #-}

      type Frozen g = (f :: Type) | f -> g
      freezeGen :: g s -> m (Frozen g)
      thawGen :: Frozen g -> m (g s)

      uniformWord32 :: g s -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g s -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

Conceptually, in 'MonadRandom g s m', 'g s' is the type of the
generator, 's' is the state type, and 'm' the underlying monad. Via the
functional dependency 'g m -> s', the state type is determined by the
generator and monad.

'Frozen' is the type of the generator's state "at rest". It is defined
as an injective type family via 'f -> g', so there is no ambiguity as to
which 'g' any 'Frozen g' belongs to.

This definition is generic enough to accommodate, for example, the 'Gen'
type from the 'mwc-random' package, which itself abstracts over the
underlying primitive monad and state token. The documentation shows the
full 'MonadRandom Gen' instance.

Four 'MonadRandom' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
curiousleo added a commit to idontgetoutmuch/random that referenced this issue Jun 22, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

StatefulGen
-----------

This patch adds a class 'StatefulGen':

    -- | 'StatefulGen' is an interface to monadic pseudo-random number generators.
    class Monad m => StatefulGen g m where
      uniformWord32 :: g -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

In 'StatefulGen g m', 'g' is the type of the generator and 'm' the underlying
monad.

Four 'StatefulGen' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

FrozenGen
---------

This patch also introduces a class 'FrozenGen':

    -- | 'FrozenGen' is designed for stateful pseudo-random number generators
    -- that can be saved as and restored from an immutable data type.
    class StatefulGen (MutableGen f m) m => FrozenGen f m where
      type MutableGen f m = (g :: Type) | g -> f
      freezeGen :: MutableGen f m -> m f
      thawGen :: f -> m (MutableGen f m)

'f' is the type of the generator's state "at rest" and 'm' the underlying
monad. 'MutableGen' is defined as an injective type family via 'g -> f' so for
any generator 'g', the type 'f' of its at-rest state is well-defined.

Both 'StatefulGen' and 'FrozenGen' are generic enough to accommodate, for
example, the 'Gen' type from the 'mwc-random' package, which itself abstracts
over the underlying primitive monad and state token. The documentation shows
the full instances.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
curiousleo added a commit to idontgetoutmuch/random that referenced this issue Jun 22, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word8      |         14 |         0.03 |         422|
| pure/uniform/Word16     |         13 |         0.03 |         375|
| pure/uniform/Word32     |         21 |         0.03 |         594|
| pure/uniform/Word64     |         42 |         0.03 |        1283|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int8       |         15 |         0.03 |         511|
| pure/uniform/Int16      |         15 |         0.03 |         507|
| pure/uniform/Int32      |         22 |         0.03 |         749|
| pure/uniform/Int64      |         44 |         0.03 |        1405|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|
| pure/uniform/CChar      |         14 |         0.03 |         485|
| pure/uniform/CSChar     |         14 |         0.03 |         455|
| pure/uniform/CUChar     |         13 |         0.03 |         448|
| pure/uniform/CShort     |         14 |         0.03 |         473|
| pure/uniform/CUShort    |         13 |         0.03 |         457|
| pure/uniform/CInt       |         21 |         0.03 |         737|
| pure/uniform/CUInt      |         21 |         0.03 |         742|
| pure/uniform/CLong      |         43 |         0.03 |        1544|
| pure/uniform/CULong     |         42 |         0.03 |        1460|
| pure/uniform/CPtrdiff   |         43 |         0.03 |        1494|
| pure/uniform/CSize      |         43 |         0.03 |        1475|
| pure/uniform/CWchar     |         22 |         0.03 |         785|
| pure/uniform/CSigAtomic |         21 |         0.03 |         749|
| pure/uniform/CLLong     |         43 |         0.03 |        1554|
| pure/uniform/CULLong    |         42 |         0.03 |        1505|
| pure/uniform/CIntPtr    |         43 |         0.03 |        1476|
| pure/uniform/CUIntPtr   |         42 |         0.03 |        1463|
| pure/uniform/CIntMax    |         43 |         0.03 |        1535|
| pure/uniform/CUIntMax   |         42 |         0.03 |        1493|

API changes
===========

StatefulGen
-----------

This patch adds a class 'StatefulGen':

    -- | 'StatefulGen' is an interface to monadic pseudo-random number generators.
    class Monad m => StatefulGen g m where
      uniformWord32 :: g -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

In 'StatefulGen g m', 'g' is the type of the generator and 'm' the underlying
monad.

Four 'StatefulGen' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

FrozenGen
---------

This patch also introduces a class 'FrozenGen':

    -- | 'FrozenGen' is designed for stateful pseudo-random number generators
    -- that can be saved as and restored from an immutable data type.
    class StatefulGen (MutableGen f m) m => FrozenGen f m where
      type MutableGen f m = (g :: Type) | g -> f
      freezeGen :: MutableGen f m -> m f
      thawGen :: f -> m (MutableGen f m)

'f' is the type of the generator's state "at rest" and 'm' the underlying
monad. 'MutableGen' is defined as an injective type family via 'g -> f' so for
any generator 'g', the type 'f' of its at-rest state is well-defined.

Both 'StatefulGen' and 'FrozenGen' are generic enough to accommodate, for
example, the 'Gen' type from the 'mwc-random' package, which itself abstracts
over the underlying primitive monad and state token. The documentation shows
the full instances.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.10' (GHC-8.2)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
curiousleo added a commit to idontgetoutmuch/random that referenced this issue Jun 23, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|

API changes
===========

StatefulGen
-----------

This patch adds a class 'StatefulGen':

    -- | 'StatefulGen' is an interface to monadic pseudo-random number generators.
    class Monad m => StatefulGen g m where
      uniformWord32 :: g -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

In 'StatefulGen g m', 'g' is the type of the generator and 'm' the underlying
monad.

Four 'StatefulGen' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

FrozenGen
---------

This patch also introduces a class 'FrozenGen':

    -- | 'FrozenGen' is designed for stateful pseudo-random number generators
    -- that can be saved as and restored from an immutable data type.
    class StatefulGen (MutableGen f m) m => FrozenGen f m where
      type MutableGen f m = (g :: Type) | g -> f
      freezeGen :: MutableGen f m -> m f
      thawGen :: f -> m (MutableGen f m)

'f' is the type of the generator's state "at rest" and 'm' the underlying
monad. 'MutableGen' is defined as an injective type family via 'g -> f' so for
any generator 'g', the type 'f' of its at-rest state is well-defined.

Both 'StatefulGen' and 'FrozenGen' are generic enough to accommodate, for
example, the 'Gen' type from the 'mwc-random' package, which itself abstracts
over the underlying primitive monad and state token. The documentation shows
the full instances.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.8' (GHC-7.10)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
curiousleo added a commit to idontgetoutmuch/random that referenced this issue Jun 23, 2020
This patch is mostly backwards compatible. See "Breaking Changes" below
for the full list of backwards incompatible changes.

This patch fixes quality and performance issues, addresses additional
miscellaneous issues, and introduces a monadic API.

Issues addressed
================

Priority issues fixed in this patch:

- Title: "The seeds generated by split are not independent"
  Link:  haskell#25
  Fixed: changed algorithm to SplitMix, which provides a robust 'split'
  operation

- Title: "Very low throughput"
  Link:  haskell#51
  Fixed: see "Performance" below

Additional issues addressed in this patch:

- Title: "Add Random instances for tuples"
  Link:  haskell#26
  Addressed: added 'Uniform' instances for up to 6-tuples

- Title: "Add Random instance for Natural"
  Link:  haskell#44
  Addressed: added 'UniformRange' instance for 'Natural'

- Title: "incorrect distribution of randomR for floating-point numbers"
  Link:  haskell#53
  Addressed: see "Regarding floating-point numbers" below

- Title: "System/Random.hs:43:1: warning: [-Wtabs]"
  Link:  haskell#55
  Fixed: no more tabs

- Title: "Why does random for Float and Double produce exactly 24 or 53 bits?"
  Link:  haskell#58
  Fixed: see "Regarding floating-point numbers" below

- Title: "read :: StdGen fails for strings longer than 6"
  Link:  haskell#59
  Addressed: 'StdGen' is no longer an instance of 'Read'

Regarding floating-point numbers: with this patch, the relevant
instances for 'Float' and 'Double' sample more bits than before but do
not sample every possible representable value. The documentation now
clearly spells out what this means for users.

Quality (issue 25)
==================

The algorithm [1] in version 1.1 of this library fails empirical PRNG
tests when used to generate "split sequences" as proposed in [3].

SplitMix [2] passes the same tests. This patch changes 'StdGen' to use
the SplitMix implementation provided by the splitmix package.

Test batteries used: dieharder, TestU1, PractRand.

[1]: P. L'Ecuyer, "Efficient and portable combined random number
generators". https://doi.org/10.1145/62959.62969

[2]: G. L. Steele, D. Lea, C. H. Flood, "Fast splittable pseudorandom
number generators". https://doi.org/10.1145/2714064.2660195

[3]: H. G. Schaathun, "Evaluation of splittable pseudo-random
generators". https://doi.org/10.1017/S095679681500012X

Performance (issue 51)
======================

The "improvement" column in the following table is a multiplier: the
improvement for 'random' for type 'Float' is 1038, so this operation is
1038 times faster with this patch.

| Name                    | Mean (1.1) | Mean (patch) | Improvement|
| ----------------------- | ---------- | ------------ | ---------- |
| pure/random/Float       |         30 |         0.03 |        1038|
| pure/random/Double      |         52 |         0.03 |        1672|
| pure/random/Integer     |         43 |         0.33 |         131|
| pure/uniform/Word       |         44 |         0.03 |        1491|
| pure/uniform/Int        |         43 |         0.03 |        1512|
| pure/uniform/Char       |         17 |         0.49 |          35|
| pure/uniform/Bool       |         18 |         0.03 |         618|

API changes
===========

StatefulGen
-----------

This patch adds a class 'StatefulGen':

    -- | 'StatefulGen' is an interface to monadic pseudo-random number generators.
    class Monad m => StatefulGen g m where
      uniformWord32 :: g -> m Word32 -- default implementation in terms of uniformWord64
      uniformWord64 :: g -> m Word64 -- default implementation in terms of uniformWord32
      -- plus methods for other word sizes and for byte strings
      -- all have default implementations so the MINIMAL pragma holds

In 'StatefulGen g m', 'g' is the type of the generator and 'm' the underlying
monad.

Four 'StatefulGen' instances ("monadic adapters") are provided for pure
generators to enable their use in monadic code. The documentation
describes them in detail.

FrozenGen
---------

This patch also introduces a class 'FrozenGen':

    -- | 'FrozenGen' is designed for stateful pseudo-random number generators
    -- that can be saved as and restored from an immutable data type.
    class StatefulGen (MutableGen f m) m => FrozenGen f m where
      type MutableGen f m = (g :: Type) | g -> f
      freezeGen :: MutableGen f m -> m f
      thawGen :: f -> m (MutableGen f m)

'f' is the type of the generator's state "at rest" and 'm' the underlying
monad. 'MutableGen' is defined as an injective type family via 'g -> f' so for
any generator 'g', the type 'f' of its at-rest state is well-defined.

Both 'StatefulGen' and 'FrozenGen' are generic enough to accommodate, for
example, the 'Gen' type from the 'mwc-random' package, which itself abstracts
over the underlying primitive monad and state token. The documentation shows
the full instances.

'Uniform' and 'UniformRange'
----------------------------

The 'Random' typeclass has conceptually been split into 'Uniform' and
'UniformRange'. The 'Random' typeclass is still included for backwards
compatibility. 'Uniform' is for types where it is possible to sample
from the type's entire domain; 'UniformRange' is for types where one can
sample from a specified range.

Breaking Changes
================

This patch introduces these breaking changes:

* requires 'base >= 4.8' (GHC-7.10)
* 'StdGen' is no longer an instance of 'Read'
* 'randomIO' and 'randomRIO' where extracted from the 'Random' class into
  separate functions

In addition, there may be import clashes with new functions, e.g. 'uniform' and
'uniformR'.

Deprecations
============

This patch introduces 'genWord64', 'genWord32' and similar methods to
the 'RandomGen' class. The significantly slower method 'next' and its
companion 'genRange' are now deprecated.

Co-authored-by: Alexey Kuleshevich <[email protected]>
Co-authored-by: idontgetoutmuch <[email protected]>
Co-authored-by: Leonhard Markert <[email protected]>
@lehins
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lehins commented Jun 23, 2020

All compile time warnings have been taken care of. See #62

@lehins lehins closed this as completed Jun 23, 2020
@lehins lehins added this to the 1.2.0 milestone Jan 23, 2021
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