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Improve performance of Philox64. #9

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Apr 17, 2024
Merged

Improve performance of Philox64. #9

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44 changes: 21 additions & 23 deletions lib/philox.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -72,20 +72,22 @@ end = struct
and key = uint64 * uint64


let bumpkey (x, y) =
Uint64.(x + Uint64.of_string "0x9E3779B97F4A7C15",
y + Uint64.of_string "0xBB67AE8584CAA73B")
let bumpk0 = Uint64.of_string "0x9E3779B97F4A7C15"
and bumpk1 = Uint64.of_string "0xBB67AE8584CAA73B"
let bumpkey (x, y) = Uint64.(x + bumpk0, y + bumpk1)


let mulhilo64 a b =
let p = Uint128.(of_uint64 a * of_uint64 b) in
Uint128.(shift_right p 64 |> to_uint64, to_uint64 p)


let rh0 =Uint64.of_string "0xD2E7470EE14C6C93"
and rh1 = Uint64.of_string "0xCA5A826395121157"
let round (c0, c1, c2, c3) (k0, k1) =
let hi0, lo0 = mulhilo64 (Uint64.of_string "0xD2E7470EE14C6C93") c0 in
let hi1, lo1 = mulhilo64 (Uint64.of_string "0xCA5A826395121157") c2 in
Uint64.(logxor hi1 c1 |> logxor k0, lo1, logxor hi0 c3 |> logxor k1, lo0)
match mulhilo64 rh0 c0, mulhilo64 rh1 c2 with
| (hi0, lo0), (hi1, lo1) -> Uint64.(logxor hi1 c1 |> logxor k0, lo1,
logxor hi0 c3 |> logxor k1, lo0)


let ten_rounds ctr key =
Expand All @@ -100,11 +102,11 @@ end = struct

let next (c0, c1, c2, c3) =
let open Uint64 in
match c0 + one = zero, c1 + one = zero, c2 + one = zero with
| true, true, true -> (c0 + one, c1 + one, c2 + one, c3 + one)
| true, true, false -> (c0 + one, c1 + one, c2 + one, c3)
| true, false, false -> (c0 + one, c1 + one, c2, c3)
| _, _, _ -> (c0 + one, c1, c2, c3)
match c0 + one, c1 + one, c2 + one with
| c0', c1', c2' when (c0' = zero && c1' = zero && c2' = zero) -> (c0', c1', c2', c3 + one)
| c0', c1', c2' when (c0' = zero && c1' = zero) -> (c0', c1', c2', c3)
| c0', c1', _ when c0' = zero -> (c0', c1', c2, c3)
| c0', _, _ -> (c0', c1, c2, c3)


let to_array (c0, c1, c2, c3) = [| c0; c1; c2; c3 |]
Expand All @@ -124,18 +126,14 @@ end = struct
| true -> t.uinteger, {t with has_uint32 = false}
| false ->
let uint, t' = next_uint64 t in
Uint64.(of_int 0xffffffff |> logand uint |> to_uint32),
{t' with
has_uint32 = true;
uinteger = Uint64.(shift_right uint 32 |> to_uint32)}


let next_double t =
let uint, t' = next_uint64 t in
Uint64.shift_right uint 11
|> Uint64.to_string
|> Float.of_string
|> Float.mul (1.0 /. 9007199254740992.0), t'
Uint64.(of_int 0xffffffff |> logand uint |> to_uint32), (* low 32 bits *)
{t' with has_uint32 = true;
uinteger = Uint64.(shift_right uint 32 |> to_uint32)} (* high 32 bits *)


let next_double t = match next_uint64 t with
| u, t' ->
Uint64.(shift_right u 11 |> to_int) |> Float.of_int |> ( *. ) (1.0 /. 9007199254740992.0), t'


let jump t =
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