8000 ENH: Make numpy floor_divide and remainder agree with Python `//` and `%`. by charris · Pull Request #7258 · numpy/numpy · GitHub
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ENH: Make numpy floor_divide and remainder agree with Python // and %. #7258

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Merged
merged 6 commits into from
Feb 21, 2016
Merged

ENH: Make numpy floor_divide and remainder agree with Python // and %. #7258

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25c23f1
ENH: Add new npy_divmod function to npy_math.
charris Feb 15, 2016
8556c5d
ENH: Make numpy floating scalars consistent with Python divmod.
charris Feb 15, 2016
fbeae17
MAINT: Remove floor function code no longer needed in scalarmath.
charris Feb 16, 2016
735174b
ENH: Make numpy ufuncs compatible with Python divmod.
charris Feb 16, 2016
e8302fd
TST: Add tests for '//' and '%' (floor_divide, remainder).
charris Feb 16, 2016
542c88b
DOC: Document that floor_divide and remainder are complementary.
charris Feb 19, 2016
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ENH: Make numpy ufuncs compatible with Python divmod. 
The following numpy ufuncs are reimplemented using the npy_divmod
function.

- remainder ('%')
- floor_divide ('//')

Example of differences

Currently

    In [1]: a = np.array(78 * 6e-8)

    In [2]: b = np.array(6e-8)

    In [3]: a // b
    Out[3]: 77.0

    In [4]: a % b
    Out[4]: 5.9999999999999651e-08

Previously

    In [1]: a = np.array(78 * 6e-8)

    In [2]: b = np.array(6e-8)

    In [3]: a // b
    Out[3]: 78.0

    In [4]: a % b
    Out[4]: 0.0

The first agrees with the Python values for the same operation and is a
bit more accurate for the input values as represented internally.

Closes #7224.
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@charris
charris committed Feb 19, 2016
commit 735174b88768999a2247f960669185978587408a
25 changes: 10 additions & 15 deletions numpy/core/src/umath/loops.c.src
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Original file line number Diff line number Diff line change
Expand Up @@ -1696,7 +1696,8 @@ NPY_NO_EXPORT void
BINARY_LOOP {
const @type@ in1 = *(@type@ *)ip1;
const @type@ in2 = *(@type@ *)ip2;
*((@type@ *)op1) = npy_floor@c@(in1/in2);
@type@ mod;
*((@type@ *)op1) = npy_divmod@c@(in1, in2, &mod);
}
}

Expand All @@ -1706,8 +1707,7 @@ NPY_NO_EXPORT void
BINARY_LOOP {
const @type@ in1 = *(@type@ *)ip1;
const @type@ in2 = *(@type@ *)ip2;
const @type@ div = in1/in2;
*((@type@ *)op1) = in2*(div - npy_floor@c@(div));
npy_divmod@c@(in1, in2, (@type@ *)op1);
}
}

Expand Down Expand Up @@ -2011,25 +2011,20 @@ NPY_NO_EXPORT void
HALF_floor_divide(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
{
BINARY_LOOP {
const float in1 = npy_half_to_float(*(npy_half *)ip1);
const float in2 = npy_half_to_float(*(npy_half *)ip2);
*((npy_half *)op1) = npy_float_to_half(npy_floorf(in1/in2));
const npy_half in1 = *(npy_half *)ip1;
const npy_half in2 = *(npy_half *)ip2;
npy_half mod;
*((npy_half *)op1) = npy_half_divmod(in1, in2, &mod);
}
}

NPY_NO_EXPORT void
HALF_remainder(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func))
{
BINARY_LOOP {
const float in1 = npy_half_to_float(*(npy_half *)ip1);
const float in2 = npy_half_to_float(*(npy_half *)ip2);
const float res = npy_fmodf(in1,in2);
if (res && ((in2 < 0) != (res < 0))) {
*((npy_half *)op1) = npy_float_to_half(res + in2);
}
else {
*((npy_half *)op1) = npy_float_to_half(res);
}
const npy_half in1 = *(npy_half *)ip1;
const npy_half in2 = *(npy_half *)ip2;
npy_half_divmod(in1, in2, (npy_half *)op1);
}
}

Expand Down
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