8000 ENH: Changes (and tests) to allow exporting half-floats through the b… · numpy/numpy@f9c7bde · GitHub
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Eli Stevensmwiebe
Eli Stevens
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ENH: Changes (and tests) to allow exporting half-floats through the buffer interface. (#1789)
Code: Added NPY_HALF to switch (descr->type_num) in _buffer_format_string. Added 'e' keys to the _pep3118_native_map and _pep3118_standard_map. Tests: Added entries to the generic round-trip tests. Added specialized half-float test that round-trips example values from the wikipedia page. http://en.wikipedia.org/wiki/Half_precision_floating-point_format http://mail.scipy.org/pipermail/numpy-discussion/2011-March/055795.html
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‎numpy/core/_internal.py

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@@ -363,6 +363,7 @@ def _index_fields(ary, fields):
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'L': 'L',
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'q': 'q',
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'Q': 'Q',
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'e': 'e',
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'f': 'f',
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'd': 'd',
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'g': 'g',
@@ -388,6 +389,7 @@ def _index_fields(ary, fields):
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'L': 'u4',
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'q': 'i8',
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'Q': 'u8',
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'e': 'f2',
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'f': 'f',
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'd': 'd',
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'Zf': 'F',

‎numpy/core/src/multiarray/buffer.c

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@@ -358,6 +358,7 @@ _buffer_format_string(PyArray_Descr *descr, _tmp_string_t *str,
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break;
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case NPY_LONGLONG: if (_append_char(str, 'q')) return -1; break;
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case NPY_ULONGLONG: if (_append_char(str, 'Q')) return -1; break;
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case NPY_HALF: if (_append_char(str, 'e')) return -1; break;
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case NPY_FLOAT: if (_append_char(str, 'f')) return -1; break;
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case NPY_DOUBLE: if (_append_char(str, 'd')) return -1; break;
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case NPY_LONGDOUBLE: if (_append_char(str, 'g')) return -1; break;

‎numpy/core/tests/test_multiarray.py

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@@ -2008,9 +2008,11 @@ def test_roundtrip(self):
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('l', 'S4'),
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('m', 'U4'),
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('n', 'V3'),
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('o', '?')]
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('o', '?'),
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('p', np.half),
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]
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x = np.array([(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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asbytes('aaaa'), 'bbbb', asbytes('xxx'), True)],
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asbytes('aaaa'), 'bbbb', asbytes('xxx'), True, 1.0)],
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dtype=dt)
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self._check_roundtrip(x)
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@@ -2042,6 +2044,25 @@ def test_roundtrip(self):
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x = np.array([1,2,3], dtype='<q')
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assert_raises(ValueError, self._check_roundtrip, x)
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def test_roundtrip_half(self):
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half_list = [
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1.0,
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-2.0,
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6.5504 * 10**4, # (max half precision)
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2**-14, # ~= 6.10352 * 10**-5 (minimum positive normal)
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2**-24, # ~= 5.96046 * 10**-8 (minimum strictly positive subnormal)
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0.0,
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-0.0,
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float('+inf'),
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float('-inf'),
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0.333251953125, # ~= 1/3
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]
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x = np.array(half_list, dtype='>e')
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self._check_roundtrip(x)
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x = np.array(half_list, dtype='<e')
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self._check_roundtrip(x)
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def test_export_simple_1d(self):
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x = np.array([1,2,3,4,5], dtype='i')
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y = memoryview(x)
@@ -2092,9 +2113,11 @@ def test_export_record(self):
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('l', 'S4'),
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('m', 'U4'),
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('n', 'V3'),
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('o', '?')]
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('o', '?'),
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('p', np.half),
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]
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x = np.array([(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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asbytes('aaaa'), 'bbbb', asbytes(' '), True)],
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asbytes('aaaa'), 'bbbb', asbytes(' '), True, 1.0)],
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dtype=dt)
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y = memoryview(x)
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assert_equal(y.shape, (1,))
@@ -2103,9 +2126,9 @@ def test_export_record(self):
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sz = sum([dtype(b).itemsize for a, b in dt])
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if dtype('l').itemsize == 4:
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assert_equal(y.format, 'T{b:a:=h:b:i:c:l:d:^q:dx:B:e:@H:f:=I:g:L:h:^Q:hx:=f:i:d:j:^g:k:=Zf:ix:Zd:jx:^Zg:kx:4s:l:=4w:m:3x:n:?:o:}')
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assert_equal(y.format, 'T{b:a:=h:b:i:c:l:d:^q:dx:B:e:@H:f:=I:g:L:h:^Q:hx:=f:i:d:j:^g:k:=Zf:ix:Zd:jx:^Zg:kx:4s:l:=4w:m:3x:n:?:o:@e:p:}')
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else:
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assert_equal(y.format, 'T{b:a:=h:b:i:c:q:d:^q:dx:B:e:@H:f:=I:g:Q:h:^Q:hx:=f:i:d:j:^g:k:=Zf:ix:Zd:jx:^Zg:kx:4s:l:=4w:m:3x:n:?:o:}')
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assert_equal(y.format, 'T{b:a:=h:b:i:c:q:d:^q:dx:B:e:@H:f:=I:g:Q:h:^Q:hx:=f:i:d:j:^g:k:=Zf:ix:Zd:jx:^Zg:kx:4s:l:=4w:m:3x:n:?:o:@e:p:}')
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assert_equal(y.strides, (sz,))
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assert_equal(y.itemsize, sz)
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