10000 BUG: Potential fix for divmod(1.0, 0.0) to raise divbyzero and return inf by anirudh2290 · Pull Request #16161 · numpy/numpy · GitHub
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BUG: Potential fix for divmod(1.0, 0.0) to raise divbyzero and return inf #16161

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Merged
merged 6 commits into from
Nov 25, 2020
Merged

BUG: Potential fix for divmod(1.0, 0.0) to raise divbyzero and return inf #16161

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64e525d
BUG: Potential fix for 1//0 to raise divbyzero and return inf
anirudh2290 May 4, 2020
d08bdba
ENH: divmod(inf, inf) should raise invalid error on all platforms
anirudh2290 May 18, 2020
7f55958
TST: Add additional tests for divmod, remainder and fmod
anirudh2290 May 19, 2020
8466526
MAINT: set invalid flag in fmod and cleanup divmod
anirudh2290 May 21, 2020
a6e7629
MAINT: Address review comments from Sebastian
anirudh2290 May 27, 2020
f527a57
ENH, MAINT: Add support for nan corner case and add tests
anirudh2290 Jun 2, 2020
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BUG: Potential fix for 1//0 to raise divbyzero and return inf
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@anirudh2290
anirudh2290 committed Jun 5, 2020
commit 64e525d4333e5cac8d04debfe205cb779f0e4d68
40 changes: 39 additions & 1 deletion numpy/core/src/npymath/npy_math_internal.h.src
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Original file line number Diff line number Diff line change
Expand Up @@ -624,6 +624,39 @@ NPY_INPLACE @type@ npy_logaddexp2@c@(@type@ x, @type@ y)
}
}

/*
* Wrapper function for remainder edge cases
* Internally calls npy_divmod*
*/
NPY_INPLACE @type@
npy_remainder@c@(@type@ a, @type@ b)
{
@type@ mod;
if (!b) {
mod = npy_fmod@c@(a, b);
npy_set_floatstatus_invalid();
} else {
npy_divmod@c@(a, b, &mod);
}
return mod;
}

NPY_INPLACE @type@
npy_floor_divide@c@(@type@ a, @type@ b) {
@type@ div, mod;
if (!b) {
div = a / b;
if (!a) {
npy_set_floatstatus_invalid();
} else {
npy_set_floatstatus_divbyzero();
}
} else {
div = npy_divmod@c@(a, b, &mod);
}
return div;
}

/*
* Python version of divmod.
*
Expand All @@ -637,9 +670,14 @@ npy_divmod@c@(@type@ a, @type@ b, @type@ *modulus)
mod = npy_fmod@c@(a, b);

if (!b) {
div = a / b;
npy_set_floatstatus_invalid();
if (a) {
npy_set_floatstatus_divbyzero();
}
/* If b == 0, return result of fmod. For IEEE is nan */
*modulus = mod;
return mod;
return div;
}

/* a - mod should be very nearly an integer multiple of b */
Expand Down
20 changes: 14 additions & 6 deletions numpy/core/src/umath/loops.c.src
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Expand Up @@ -2004,8 +2004,7 @@ NPY_NO_EXPORT void
BINARY_LOOP {
const @type@ in1 = *(@type@ *)ip1;
const @type@ in2 = *(@type@ *)ip2;
@type@ mod;
*((@type@ *)op1) = npy_divmod@c@(in1, in2, &mod);
*((@type@ *)op1) = npy_floor_divide@c@(in1, in2);
}
}

Expand All @@ -2015,7 +2014,7 @@ NPY_NO_EXPORT void
BINARY_LOOP {
const @type@ in1 = *(@type@ *)ip1;
const @type@ in2 = *(@type@ *)ip2;
npy_divmod@c@(in1, in2, (@type@ *)op1);
*((@type@ *) op1) = npy_remainder@c@(in1, in2);
}
}

Expand Down Expand Up @@ -2360,8 +2359,13 @@ HALF_floor_divide(char **args, npy_intp const *dimensions, npy_intp const *steps
BINARY_LOOP {
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);

float fh1 = npy_half_to_float(in1);
float fh2 = npy_half_to_float(in2);
float div;

div = npy_floor_dividef(fh1, fh2);
*((npy_half *)op1) = npy_float_to_half(div);
}
}

Expand All @@ -2371,7 +2375,11 @@ HALF_remainder(char **args, npy_intp const *dimensions, npy_intp const *steps, v
BINARY_LOOP {
const npy_half in1 = *(npy_half *)ip1;
const npy_half in2 = *(npy_half *)ip2;
npy_half_divmod(in1, in2, (npy_half *)op1);
float fh1 = npy_half_to_float(in1);
float fh2 = npy_half_to_float(in2);
float mod;
mod = npy_remainderf(fh1, fh2);
*((npy_half *)op1) = npy_float_to_half(mod);
}
}

Expand Down
12 changes: 10 additions & 2 deletions numpy/core/src/umath/scalarmath.c.src
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Expand Up @@ -285,7 +285,11 @@ static void
@name@_ctype_floor_divide(@type@ a, @type@ b, @type@ *out) {
@type@ mod;

*out = npy_divmod@c@(a, b, &mod);
if (!b) {
*out = a / b;
} else {
*out = npy_divmod@c@(a, b, &mod);
}
}


Expand Down Expand Up @@ -318,7 +322,11 @@ static void
half_ctype_floor_divide(npy_half a, npy_half b, npy_half *out) {
npy_half mod;

*out = npy_half_divmod(a, b, &mod);
if (!b) {
*out = a / b;
} else {
*out = npy_half_divmod(a, b, &mod);
}
}


Expand Down
7 changes: 7 additions & 0 deletions numpy/core/tests/test_scalarmath.py
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Expand Up @@ -276,6 +276,10 @@ def test_float_modulus_corner_cases(self):
# Check nans, inf
with suppress_warnings() as sup:
sup.filter(RuntimeWarning, "invalid value encountered in remainder")
sup.filter(RuntimeWarning, "divide by zero encountered in remainder")
sup.filter(RuntimeWarning, "divide by zero encountered in floor_divide")
sup.filter(RuntimeWarning, "divide by zero encountered in divmod")
sup.filter(RuntimeWarning, "invalid value encountered in divmod")
for dt in np.typecodes['Float']:
fone = np.array(1.0, dtype=dt)
fzer = np.array(0.0, dtype=dt)
Expand All @@ -290,6 +294,9 @@ def test_float_modulus_corner_cases(self):
assert_(np.isnan(rem), 'dt: %s' % dt)
rem = operator.mod(finf, fone)
assert_(np.isnan(rem), 'dt: %s' % dt)
for op in [floordiv_and_mod, divmod]:
div, mod = op(fone, fzer)
assert_(np.isinf(div)) and assert_(np.isnan(mod))

def test_inplace_floordiv_handling(self):
# issue gh-12927
Expand Down
52 changes: 51 additions & 1 deletion numpy/core/tests/test_umath.py
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Expand Up @@ -13,7 +13,7 @@
assert_, assert_equal, assert_raises, assert_raises_regex,
assert_array_equal, assert_almost_equal, assert_array_almost_equal,
assert_array_max_ulp, assert_allclose, assert_no_warnings, suppress_warnings,
_gen_alignment_data, assert_array_almost_equal_nulp
_gen_alignment_data, assert_array_almost_equal_nulp, assert_warns
)

def on_powerpc():
A3E2 Expand Down Expand Up @@ -293,6 +293,19 @@ def test_floor_division_signed_zero(self):
assert_equal(np.signbit(x//1), 0)
assert_equal(np.signbit((-x)//1), 1)

@pytest.mark.parametrize('dtype', np.typecodes['Float'])
def test_floor_division_corner_cases(self, dtype):
# test corner cases like 1.0//0.0 for errors and return vals
x = np.zeros(10, dtype=dtype)
y = np.ones(10, dtype=dtype)
# divide by zero error check
with np.errstate(divide='raise', invalid='ignore'):
assert_raises(FloatingPointError, np.floor_divide, y, x)
# verify 1.0//0.0 computations return inf
with np.errstate(divide='ignore'):
z = np.floor_divide(y, x)
assert_(np.isinf(z).all())

def floor_divide_and_remainder(x, y):
return (np.floor_divide(x, y), np.remainder(x, y))

Expand Down Expand Up @@ -366,6 +379,32 @@ def test_float_remainder_roundoff(self):
else:
assert_(b > rem >= 0, msg)

@pytest.mark.parametrize('dtype', np.typecodes['Float'])
def test_float_remainder_errors(self, dtype):
# Check valid errors raised for divmod and remainder
fzero = np.array(0.0, dtype=dtype)
fone = np.array(1.0, dtype=dtype)
finf = np.array(np.inf, dtype=dtype)
with np.errstate(invalid='raise'):
assert_raises(FloatingPointError, np.remainder, fone, fzero)
# since divmod is combination of both remainder and divide
# ops it will set both dividebyzero and invalid flags
with np.errstate(divide='raise', invalid='ignore'):
assert_raises(FloatingPointError, np.divmod, fone, fzero)
with np.errstate(divide='ignore', invalid='raise'):
assert_raises(FloatingPointError, np.divmod, fone, fzero)
with np.errstate(invalid='raise'):
assert_raises(FloatingPointError, np.divmod, fzero, fzero)
with np.errstate(invalid='raise'):
assert_raises(FloatingPointError, np.divmod, finf, finf)

def test_float_remainder_overflow(self):
a = np.finfo(np.float64).tiny
with np.errstate(over='ignore', invalid='ignore'):
div, mod = np.divmod(4, a)
np.isinf(div)
assert_(mod == 0)
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Should we test that these warnings are given, or did that fail on some hardware?

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we ensure the errors invalid and dividebyzero are raised for divmod in line 370 to 373. Is this what you are looking for ?

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Yeah, I guess I meant the specific case for tiny.


def test_float_remainder_corner_cases(self):
# Check remainder magnitude.
for dt in np.typecodes['Float']:
Expand All @@ -379,20 +418,31 @@ def test_float_remainder_corner_cases(self):
# Check nans, inf
with suppress_warnings() as sup:
sup.filter(RuntimeWarning, "invalid value encountered in remainder")
sup.filter(RuntimeWarning, "invalid value encountered in divmod")
sup.filter(RuntimeWarning, "divide by zero encountered in divmod")
for dt in np.typecodes['Float']:
fone = np.array(1.0, dtype=dt)
fzer = np.array(0.0, dtype=dt)
finf = np.array(np.inf, dtype=dt)
fnan = np.array(np.nan, dtype=dt)
rem = np.remainder(fone, fzer)
assert_(np.isnan(rem), 'dt: %s, rem: %s' % (dt, rem))
div, rem = np.divmod(fone, fzer)
assert_(np.isinf(div), 'dt: %s, div: %s' % (dt, rem))
assert_(np.isnan(rem), 'dt: %s, rem: %s' % (dt, rem))
# MSVC 2008 returns NaN here, so disable the check.
#rem = np.remainder(fone, finf)
#assert_(rem == fone, 'dt: %s, rem: %s' % (dt, rem))
rem = np.remainder(fone, fnan)
assert_(np.isnan(rem), 'dt: %s, rem: %s' % (dt, rem))
rem = np.remainder(finf, fone)
assert_(np.isnan(rem), 'dt: %s, rem: %s' % (dt, rem))
div, rem = np.divmod(fzer, fzer)
assert_(np.isnan(rem), 'dt: %s, rem: %s' % (dt, rem))
assert_(np.isnan(div), 'dt: %s, rem: %s' % (dt, rem))
div, rem = np.divmod(finf, finf)
assert_(np.isnan(div), 'dt: %s, rem: %s' % (dt, rem))
assert_(np.isnan(rem), 'dt: %s, rem: %s' % (dt, rem))


class TestCbrt:
Expand Down
0