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Preserve the imaginary zero sign in complex log1p #1438

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Preserve the imaginary zero sign in complex log1p #1438

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2 changes: 1 addition & 1 deletion include/xsimd/arch/common/xsimd_common_math.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1873,7 +1873,7 @@ namespace xsimd
{
using batch_type = batch<std::complex<T>, A>;
using real_batch = typename batch_type::real_batch;
batch_type u = 1 + self;
batch_type u(real_batch(1.) + self.real(), self.imag());
batch_type logu = log(u);
return select(u == batch_type(1.),
self,
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48 changes: 48 additions & 0 deletions test/test_complex_exponential.cpp
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Expand Up @@ -213,4 +213,52 @@ TEST_CASE_TEMPLATE("[complex exponential]", B, BATCH_COMPLEX_TYPES)
Test.test_sign();
}
}
#ifndef __FAST_MATH__
TEST_CASE_TEMPLATE("[complex log1p branch cut]", 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 auto below = std::nextafter(real_type(-1), real_type(-2));
const std::array<value_type, 14> samples = {
value_type(-4, zero), value_type(-4, -zero),
value_type(-2, zero), value_type(-2, -zero),
value_type(below, zero), value_type(below, -zero),
value_type(-2, real_type(0.5)), value_type(-2, real_type(-0.5)),
value_type(real_type(-0.5), real_type(0.25)), value_type(real_type(-0.5), real_type(-0.25)),
value_type(2, 1), value_type(2, -1),
value_type(zero, zero), value_type(zero, -zero)
};
std::array<value_type, B::size> inputs;
std::array<value_type, B::size> results;
const auto tolerance = real_type(64) * std::numeric_limits<real_type>::epsilon();
for (size_t start = 0; start < samples.size(); ++start)
{
for (size_t lane = 0; lane < B::size; ++lane)
{
inputs[lane] = samples[(start + lane) % samples.size()];
}
xsimd::log1p(B::load_unaligned(inputs.data())).store_unaligned(results.data());
for (size_t lane = 0; lane < B::size; ++lane)
{
const auto expected = std::log(value_type(real_type(1) + inputs[lane].real(), inputs[lane].imag()));
if (std::isinf(expected.real()))
{
CHECK(std::isinf(results[lane].real()));
CHECK_EQ(std::signbit(results[lane].real()), std::signbit(expected.real()));
}
else
{
CHECK_EQ(results[lane].real(), doctest::Approx(expected.real()).epsilon(tolerance).scale(1));
}
CHECK_EQ(results[lane].imag(), doctest::Approx(expected.imag()).epsilon(tolerance).scale(1));
CHECK_EQ(std::signbit(results[lane].imag()), std::signbit(expected.imag()));
if (expected.imag() == zero)
{
CHECK_EQ(results[lane].imag(), zero);
}
}
}
}
#endif
#endif