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compiler: Fix code generation for pow and fabs when using float32 #2504

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merged 9 commits into from
Dec 23, 2024
Merged

compiler: Fix code generation for pow and fabs when using float32 #2504

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5e98bec
sympy: Update printer to better handle precision for Pow and Abs
JDBetteridge Dec 20, 2024
7114100
tests: Add test to exercise pow and abs functionality, Fix test_integ…
JDBetteridge Dec 20, 2024
9630b13
misc: Typo
JDBetteridge Dec 20, 2024
3b6ae7e
misc: Add f-string
JDBetteridge Dec 20, 2024
9753118
sympy: Remove namespacing and tidy
JDBetteridge Dec 20, 2024
b6a3a4a
docs: Update jupyter notebooks
JDBetteridge Dec 20, 2024
e034211
Revert "docs: Update jupyter notebooks"
JDBetteridge Dec 20, 2024
8e3090e
docs: Update jupyter notebooks, second attempt
JDBetteridge Dec 20, 2024
ad97f5e
tests: Make maths functions precision tests more stringent
JDBetteridge Dec 20, 2024
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40 changes: 29 additions & 11 deletions devito/symbolics/printer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,10 @@

from mpmath.libmp import prec_to_dps, to_str
from packaging.version import Version
from numbers import Real

from sympy.core import S
from sympy.core.numbers import equal_valued, Float
from sympy.logic.boolalg import BooleanFunction
from sympy.printing.precedence import PRECEDENCE_VALUES, precedence
from sympy.printing.c import C99CodePrinter
Expand Down Expand Up @@ -122,15 +125,21 @@ def _print_math_func(self, expr, nest=False, known=None):
return f'{cname}({args})'

def _print_Pow(self, expr):
# Need to override because of issue #1627
# E.g., (Pow(h_x, -1) AND h_x.dtype == np.float32) => 1.0F/h_x
try:
if expr.exp == -1 and self.single_prec():
PREC = precedence(expr)
return '1.0F/%s' % self.parenthesize(expr.base, PREC)
except AttributeError:
pass
return super()._print_Pow(expr)
# Completely reimplement `_print_Pow` from sympy, since it doesn't
# correctly handle precision
if "Pow" in self.known_functions:
return self._print_Function(expr)
PREC = precedence(expr)
suffix = 'f' if self.single_prec(expr) else ''
if equal_valued(expr.exp, -1):
return self._print_Float(Float(1.0)) + '/' + \
self.parenthesize(expr.base, PREC)
elif equal_valued(expr.exp, 0.5):
return f'sqrt{suffix}({self._print(expr.base)})'
elif expr.exp == S.One/3 and self.standard != 'C89':
return f'cbrt{suffix}({self._print(expr.base)})'
else:
return f'pow{suffix}({self._print(expr.base)}, {self._print(expr.exp)})'

def _print_Mod(self, expr):
"""Print a Mod as a C-like %-based operation."""
Expand Down Expand Up @@ -159,8 +168,17 @@ def _print_Abs(self, expr):
if isinstance(self.compiler, AOMPCompiler):
return "fabs(%s)" % self._print(expr.args[0])
# Check if argument is an integer
func = "abs" if has_integer_args(*expr.args[0].args) else "fabs"
return "%s(%s)" % (func, self._print(expr.args[0]))
if has_integer_args(*expr.args[0].args):
func = "abs"
elif self.single_prec(expr):
func = "fabsf"
elif any([isinstance(a, Real) for a in expr.args[0].args]):
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From the look of it this seems un-necessary. You just need

If self.single_prec(expr) or self.single_prec():
    fabsf
else:
    # not integer or f32, default 
    fabs

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Not so, this is the example that I shared on slack, but will repeat here for reference:

>>> i1 = Dimension(name="i1")
>>> sympy_dtype(i1 - 0.5)
<class 'numpy.int32'>

In the second part of the or in your example self.single_prec() will always return True, regardless of the types of the expression (unless the default is changed).

This code is a bit horrible, but ensures that the "default" is only used if there is a floating point number whose type cannot be determined. Otherwise strictly use the correct function call for float or double.

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@JDBetteridge JDBetteridge Dec 20, 2024 •
edited
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Ah, but my test is wrong anyway... Okay the test is fine, the issue is trying to detect numpy float32 or float64 as sympy eagerly squashes them to a sympy.core.numbers.Float.

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I'm going to merge this, but perhaps in a subsequent PR you could attach a comment to that if

# The previous condition isn't sufficient to detect case with
# Python `float`s in that case, fall back to the "default"
func = "fabsf" if self.single_prec() else "fabs"
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I can see two self.single_prec tests. Isn;t this redundant here?
Can it be one check?

else:
func = "fabs"
return f"{func}({self._print(expr.args[0])})"

def _print_Add(self, expr, order=None):
""""
Expand Down
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