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Fix integer overflow in remainder operator #5906

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Merged
soumith merged 4 commits into from
Mar 21, 2018
Merged

Fix integer overflow in remainder operator #5906

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953a620
Fix integer overflow in remainder
vedanuj Mar 20, 2018
e3d50a4
Fix remainder operator in CUDA
vedanuj Mar 20, 2018
294d391
Add tests for remainder integer overflow
vedanuj Mar 20, 2018
2431744
Add has_different_sign static function
vedanuj Mar 20, 2018
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10 changes: 7 additions & 3 deletions aten/src/TH/generic/THTensorMath.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1052,6 +1052,10 @@ void THTensor_(fmod)(THTensor *r_, THTensor *t, real value)
}
}

static inline bool has_different_sign(real a, real b) {
return (a < 0) != (b < 0);
}

void THTensor_(remainder)(THTensor *r_, THTensor *t, real value)
{
THTensor_(resizeAs)(r_, t);
Expand All @@ -1070,7 +1074,7 @@ void THTensor_(remainder)(THTensor *r_, THTensor *t, real value)
#else
// There is no NAN for integers
rp[i] = tp[i] % value;
if (rp[i] * value < 0)
if (has_different_sign(rp[i], value))
rp[i] += value;
#endif
}
Expand All @@ -1085,7 +1089,7 @@ void THTensor_(remainder)(THTensor *r_, THTensor *t, real value)
#else
// There is no NAN for integers
TH_TENSOR_APPLY2_OMP(r_Size, r_Contig, tContig, real, r_, real, t, *r__data = *t_data % value;
if (*r__data * value < 0) *r__data += value;);
if (has_different_sign(*r__data, value)) *r__data += value;);
#endif
}
#else
Expand All @@ -1098,7 +1102,7 @@ void THTensor_(remainder)(THTensor *r_, THTensor *t, real value)
#else
// There is no NAN for integers
TH_TENSOR_APPLY2(real, r_, real, t, *r__data = *t_data % value;
if (*r__data * value < 0) *r__data += value;);
if (has_different_sign(*r__data, value)) *r__data += value;);
#endif
}
}
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5 changes: 5 additions & 0 deletions aten/src/THC/THCNumerics.cuh
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Expand Up @@ -28,6 +28,11 @@ static inline __host__ __device__ scalar_t powi(scalar_t a, scalar_t b) {
return result;
}

template <typename scalar_t>
static inline __host__ __device__ bool has_different_sign(scalar_t a, scalar_t b) {
return (a < 0) != (b < 0);
}

template <>
struct THCNumerics<uint8_t> {
static inline __host__ __device__ uint8_t min() { return 0; }
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4 changes: 2 additions & 2 deletions aten/src/THC/THCTensorMathPairwise.cu
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Expand Up @@ -245,14 +245,14 @@ struct TensorRemainderOp {
TensorRemainderOp(T v) : val(v) {}
__device__ __forceinline__ void operator()(T* out, T* in) {
*out = *in % val;
if ((*out * val) < 0){
if (has_different_sign<T>(*out, val)){
*out += val;
}
}

__device__ __forceinline__ void operator()(T* v) {
*v = *v % val;
if ((*v * val) < 0){
if (has_different_sign<T>(*v, val)){
*v += val;
}
}
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3 changes: 3 additions & 0 deletions test/test_cuda.py
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Expand Up @@ -1434,6 +1434,9 @@ def test_min_max_inits(self):
def test_int_pow(self):
TestTorch._test_int_pow(self, lambda x: x.cuda())

def test_remainder_overflow(self):
TestTorch._test_remainder_overflow(self, dtype=torch.cuda.int64)

def test_var(self):
cpu_tensor = torch.randn(2, 3, 3)
gpu_tensor = cpu_tensor.cuda()
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13 changes: 13 additions & 0 deletions test/test_torch.py
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Expand Up @@ -780,6 +780,19 @@ def test_remainder(self):
long_res1 = long_m1.clone()
long_res1.remainder_(long_qs.unsqueeze(0).expand_as(long_res1))

@staticmethod
def _test_remainder_overflow(self, dtype=torch.int64):
# Check Integer Overflows
x = torch.tensor(23500, dtype=dtype)
q = 392486996410368
self.assertEqual(x % q, x)
self.assertEqual(-x % q, q - x)
self.assertEqual(x % -q, x - q)
self.assertEqual(-x % -q, -x)

def test_remainder_overflow(self):
self._test_remainder_overflow(self, dtype=torch.int64)

def test_mm(self):
# helper function
def matrixmultiply(mat1, mat2):
Expand Down