8000 Fix 1.9 alignment by charris · Pull Request #5478 · numpy/numpy · GitHub
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Fix 1.9 alignment #5478

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Merged
merged 2 commits into from
Jan 25, 2015
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Fix 1.9 alignment #5478

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e0ef28b
BUG: fix string arrays not being aligned
juliantaylor Nov 26, 2014
43e5e9e
BUG: reduce maximum alignment to 8 bytes on 32 bit
juliantaylor Nov 26, 2014
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BUG: fix string arrays not being aligned 
If itemsize is a power of two use that as the required alignment up to
the maximum provided by the platform. Power of two sizes may be accessed
via larger moves than bytes.
Non-power of two sizes are accessed bytewise and can thus always be
considered aligned.
Closes gh-5293
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@juliantaylor @charris
juliantaylor authored and charris committed Jan 22, 2015
commit e0ef28b22a04d1d470e381f1b0cee56aec4349ed
11 changes: 10 additions & 1 deletion numpy/core/src/multiarray/common.c
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Expand Up @@ -684,7 +684,16 @@ _IsAligned(PyArrayObject *ap)

/* alignment 1 types should have a efficient alignment for copy loops */
if (PyArray_ISFLEXIBLE(ap) || PyArray_ISSTRING(ap)) {
alignment = NPY_MAX_COPY_ALIGNMENT;
npy_intp itemsize = PyArray_ITEMSIZE(ap);
/* power of two sizes may be loaded in larger moves */
if (((itemsize & (itemsize - 1)) == 0)) {
alignment = itemsize > NPY_MAX_COPY_ALIGNMENT ?
NPY_MAX_COPY_ALIGNMENT : itemsize;
}
else {
/* if not power of two it will be accessed bytewise */
alignment = 1;
}
}

if (alignment == 1) {
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11 changes: 11 additions & 0 deletions numpy/core/tests/test_multiarray.py
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Expand Up @@ -68,6 +68,17 @@ def test_otherflags(self):
assert_equal(self.a.flags.aligned, True)
assert_equal(self.a.flags.updateifcopy, False)

def test_string_align(self):
a = np.zeros(4, dtype=np.dtype('|S4'))
assert_(a.flags.aligned)
# not power of two are accessed bytewise and thus considered aligned
a = np.zeros(5, dtype=np.dtype('|S4'))
assert_(a.flags.aligned)

def test_void_align(self):
a = np.zeros(4, dtype=np.dtype([("a", "i4"), ("b", "i4")]))
assert_(a.flags.aligned)

class TestHash(TestCase):
# see #3793
def test_int(self):
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0