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BUG: fix incorrect strcmp implementation for unequal length strings #25522

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Jan 3, 2024
Merged

BUG: fix incorrect strcmp implementation for unequal length strings #25522

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10 changes: 2 additions & 8 deletions numpy/_core/src/umath/string_buffer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -290,21 +290,15 @@ struct Buffer {
tmp2++;
}
while (tmp1.buf < tmp1.after) {
if (*tmp1 < 0) {
return -1;
}
if (*tmp1 > 0) {
if (*tmp1) {
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@seberg seberg Jan 3, 2024 •
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I am confused, wouldn't this make:

In [1]: "a" == "a\0"
Out[1]: False

Return True? For NumPy strings, this should be handled already earlier by the length, and for the new strings embedded 0 characters should be supported.

EDIT: Or I don't know maybe we need strcmp_padded for legacy strings...

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I'm learning new things about numpy strings every day. For some reason I thought that this was True until now, but I'm clearly wrong:

In [1]: import numpy as np

In [2]: np.__version__
Out[2]: '1.26.3'

In [3]: np.str_("a") == np.str_("a\0")
Out[3]: False

The scalar repr doesn't include the trailing nulls, which I guess makes sense but definitely added to my confusion here:

In [4]: np.str_("a\0")
Out[4]: 'a'

In [5]: repr(np.str_("a\0")) == repr(np.str_("a"))
Out[5]: True

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Although I guess the above is only true for scalars, for array elements trailing nulls are ignored in Numpy 1.26.3:

In [12]: np.array([np.str_("a\0")]) == np.array([np.str_("a")])
Out[12]: array([ True])

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Just shows that scalars are broken... they should strip nulls on construction to not inherit the unicode behavior, I guess.

return 1;
}
tmp1++;
}
while (tmp2.buf < tmp2.after) {
if (*tmp2 < 0) {
if (*tmp2) {
return -1;
}
if (*tmp2 > 0) {
return 1;
}
tmp2++;
}
return 0;
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37 changes: 22 additions & 15 deletions numpy/_core/tests/test_defchararray.py
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Original file line number Diff line number Diff line change
Expand Up @@ -157,28 +157,34 @@ def test_it(self):

class TestComparisons:
def setup_method(self):
self.A = np.array([['abc', '123'],
['789', 'xyz']]).view(np.char.chararray)
self.B = np.array([['efg', '123 '],
['051', 'tuv']]).view(np.char.chararray)
self.A = np.array([['abc', 'abcc', '123'],
['789', 'abc', 'xyz']]).view(np.char.chararray)
self.B = np.array([['efg', 'efg', '123 '],
['051', 'efgg', 'tuv']]).view(np.char.chararray)

def test_not_equal(self):
assert_array_equal((self.A != self.B), [[True, False], [True, True]])
assert_array_equal((self.A != self.B),
[[True, True, False], [True, True, True]])

def test_equal(self):
assert_array_equal((self.A == self.B), [[False, True], [False, False]])
assert_array_equal((self.A == self.B),
[[False, False, True], [False, False, False]])

def test_greater_equal(self):
assert_array_equal((self.A >= self.B), [[False, True], [True, True]])
assert_array_equal((self.A >= self.B),
[[False, False, True], [True, False, True]])

def test_less_equal(self):
assert_array_equal((self.A <= self.B), [[True, True], [False, False]])
assert_array_equal((self.A <= self.B),
[[True, True, True], [False, True, False]])

def test_greater(self):
assert_array_equal((self.A > self.B), [[False, False], [True, True]])
assert_array_equal((self.A > self.B),
[[False, False, False], [True, False, True]])

def test_less(self):
assert_array_equal((self.A < self.B), [[True, False], [False, False]])
assert_array_equal((self.A < self.B),
[[True, True, False], [False, True, False]])

def test_type(self):
out1 = np.char.equal(self.A, self.B)
Expand All @@ -191,17 +197,18 @@ class TestComparisonsMixed1(TestComparisons):

def setup_method(self):
TestComparisons.setup_method(self)
self.B = np.array([['efg', '123 '],
['051', 'tuv']], np.str_).view(np.char.chararray)
self.B = np.array(
[['efg', 'efg', '123 '],
['051', 'efgg', 'tuv']], np.str_).view(np.char.chararray)

class TestComparisonsMixed2(TestComparisons):
"""Ticket #1276"""

def setup_method(self):
TestComparisons.setup_method(self)
self.A = np.array([['abc', '123'],
['789', 'xyz']], np.str_) \
.view(np.char.chararray)
self.A = np.array(
[['abc', 'abcc', '123'],
['789', 'abc', 'xyz']], np.str_).view(np.char.chararray)

class TestInformation:
def setup_method(self):
Expand Down