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compiler: Check sympy_type returns a floating point type in the code printer #2515

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compiler: Check sympy_type returns a floating point type in the code printer #2515

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compiler: Check sympy_type returns a floating point type
JDBetteridge Jan 10, 2025
c0a7a73
sympy: Add integer assumption to dimension
JDBetteridge Jan 13, 2025
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3 changes: 3 additions & 0 deletions devito/symbolics/printer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,10 @@ def compiler(self):
return self._settings['compiler']

def single_prec(self, expr=None):
# Extract the dtype of the expression
dtype = sympy_dtype(expr) if expr is not None else self.dtype
# Check that the dtype is a floating point type
dtype = dtype if np.issubdtype(dtype, np.floating) else self.dtype
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I don't think this is valid, this will return "is float" for integer and will break a lot of cases. This is probably only necessary for some limited cases like cos but not in general

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I disagree a little bit here, the method is called single_prec not is_float. If an expression only containing integers is passed, it is unclear that the result should return anything other than the default, as determined here by self.dtype.

I could see an argument for following the sympy behaviour of returning None if the precision cannot be determined, but this won't change much as bool(None) == bool(False) == False.

In the bigger picture, there are a lot of issues coinciding here, it seems that sympy_dtype isn't quite fit for purpose and the printer is doing some rather rough type inference. Personally, I think home-grown type inference should be avoided here (at least for the purposes of this PR), but I am open to further suggestions.

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@mloubout mloubout Jan 13, 2025 •
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the method is called single_prec not is_float

Well, sure, that's the name we used when we made it, but this is effectively an is_float. This merely checks if it needs the float literal.

If an expression only containing integers is passed it is unclear that the result should return anything other than the default, as determined here by self.dtype

self.dtype is only a last resort default for expression that cannot have a type determined, the type of the expression if determined is always the one that should be used irrespective of what that type is.

return dtype in [np.float32, np.float16]

def parenthesize(self, item, level, strict=False):
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2 changes: 1 addition & 1 deletion tests/test_symbolics.py
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Expand Up @@ -313,7 +313,7 @@ def test_cos_vs_cosf():

# Doesn't make much sense, but it's legal
c = dSymbol('c', dtype=np.int32)
assert ccode(cos(c)) == "cos(c)"
assert ccode(cos(c)) == "cosf(c)"
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so ccode(Abs(c)) will be absf(c) which is incorrect it should be abs(c).

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You are correct, there is a bug here with your specific example. However, I think I introduced it in my last PR and it is specific to abs/fabsf/fabs, which I will address.

But, in this test, why should the resultant code be cos(c) over cosf(c) when c is an integer type?

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Well cos is technically not defined for integers so it will convert to float or double depending on the function used so I guess the test is broken in itself and should use a function that is valid for integers



def test_intdiv():
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