8000 BUG: longdouble with elsize 12 is never uint alignable by mattip · Pull Request #12611 · numpy/numpy · GitHub
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BUG: longdouble with elsize 12 is never uint alignable #12611

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Merged
merged 5 commits into from
Dec 26, 2018
Merged

BUG: longdouble with elsize 12 is never uint alignable #12611

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d2ec5a1
DEV: activate assert code in 32bit linux via -UNDEBUG
mattip Dec 25, 2018
16c30d0
BUG: add case for longdouble alignment size
mattip Dec 25, 2018
cb690e5
BUG: non-uint-aligned arrays were counted as uint-aligned
ahaldane Dec 26, 2018
617dbcb
Merge pull request #1 from ahaldane/mattip_align-longdouble
mattip Dec 26, 2018
de4c4ef
MAINT: improve comments
mattip Dec 26, 2018
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BUG: non-uint-aligned arrays were counted as uint-aligned
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@ahaldane
ahaldane committed Dec 26, 2018
commit cb690e5b3dac32e459a5657ea7b9083e91a27316
6 changes: 5 additions & 1 deletion numpy/core/src/common/array_assign.c
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Expand Up @@ -125,9 +125,13 @@ raw_array_is_aligned(int ndim, npy_intp *shape,

return npy_is_aligned((void *)align_check, alignment);
}
else {
else if (alignment == 1) {
return 1;
}
else {
/* always return false for alignment == 0, which means unaligned */
return 0;
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Why is alignment == 0 even a legal argument to this function?

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Maybe there is a better way to organize it... but the idea is that npy_uint_alignment, which normally returns the uint alignment, returns 0 if the type is not uint-alignable.

Then, it turned out to be convenient to allow the result of npy_uint_alignment to be passed directly to raw_array_is_aligned.

An alternative would be to check the return value of npy_uint_alignment explicitly everywhere it is used. But since it is pretty much always used as an arg to raw_array_is_aligned it seemed less complicated this way.

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changed the comment

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Thanks

}
}

NPY_NO_EXPORT int
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3 changes: 2 additions & 1 deletion numpy/core/src/common/array_assign.h
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Expand Up @@ -88,7 +88,8 @@ broadcast_strides(int ndim, npy_intp *shape,
/*
* Checks whether a data pointer + set of strides refers to a raw
* array whose elements are all aligned to a given alignment.
* alignment should be a power of two.
* alignment should be a power of two, or may be the sentinel value 0 to mean
* unaligned, in which case false is always returned.
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This comment confuses me - I read this as saying that is_aligned(..., alignment = 0) means is_unaligned(...)

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If I am not misreading you, that is what the comment is meant to say. If you pass an alignment of 0, the function always returns "not aligned". Do you mean I should say "not aligned" instead of "unaligned"?

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Right. the return value means "not aligned", but the meaning of the alignment argument is closer to "unalignable"

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fixing

*/
NPY_NO_EXPORT int
raw_array_is_aligned(int ndim, npy_intp *shape,
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3 changes: 0 additions & 3 deletions numpy/core/src/multiarray/common.h
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Expand Up @@ -223,9 +223,6 @@ npy_uint_alignment(int itemsize)
case 8:
alignment = _ALIGN(npy_uint64);
break;
case 12:
alignment = _ALIGN(npy_longdouble);
break;
case 16:
/*
* 16 byte types are copied using 2 uint64 assignments.
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0