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Preserve signed imaginary zero in complex sqrt #1433

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Preserve signed imaginary zero in complex sqrt #1433

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6 changes: 3 additions & 3 deletions include/xsimd/arch/common/xsimd_common_math.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2323,9 +2323,9 @@ namespace xsimd
real_batch ze(0.);

return select(y == ze,
select(x == ze,
batch_type(ze, ze),
select(x < ze, batch_type(ze, sqrt_x), batch_type(sqrt_x, ze))),
select(x < ze,
batch_type(ze, copysign(sqrt_x, y)),
batch_type(sqrt_x, y)),
select(x == ze,
select(y > ze, batch_type(sqrt_hy, sqrt_hy), batch_type(sqrt_hy, -sqrt_hy)),
resg));
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37 changes: 37 additions & 0 deletions test/test_complex_power.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -256,4 +256,41 @@ TEST_CASE_TEMPLATE("[complex power]", B, BATCH_COMPLEX_TYPES)
Test.test_sqrt_pp();
}
}
#ifndef __FAST_MATH__
TEST_CASE_TEMPLATE("[complex sqrt signed zero]", B, BATCH_COMPLEX_TYPES)
{
using value_type = typename B::value_type;
using real_type = typename value_type::value_type;
const real_type zero(0);
const std::array<real_type, 10> real_parts = {
-std::numeric_limits<real_type>::max(), real_type(-4), real_type(-1),
-std::numeric_limits<real_type>::denorm_min(), -zero, zero,
std::numeric_limits<real_type>::denorm_min(), real_type(1), real_type(4),
std::numeric_limits<real_type>::max()
};
std::array<value_type, B::size> inputs;
std::array<value_type, B::size> results;

for (size_t start = 0; start < 2 * real_parts.size(); ++start)
{
for (size_t lane = 0; lane < B::size; ++lane)
{
const size_t index = (start + lane) % (2 * real_parts.size());
inputs[lane] = value_type(real_parts[index / 2], index % 2 ? -zero : zero);
}

xsimd::sqrt(B::load_unaligned(inputs.data())).store_unaligned(results.data());

for (size_t lane = 0; lane < B::size; ++lane)
{
const auto expected = std::sqrt(inputs[lane]);
CHECK_EQ(results[lane].real(), expected.real());
CHECK_EQ(results[lane].imag(), expected.imag());
CHECK_EQ(std::signbit(results[lane].real()), std::signbit(expected.real()));
CHECK_EQ(std::signbit(results[lane].imag()), std::signbit(expected.imag()));
}
}
}
#endif

#endif