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Fix bugs in log1p and expm1 where repeated using statements would clobber each other.

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Add specializations for complex types since std::log1p and std::exp1m do not support complex.

(cherry picked from commit d55d392e7b1136655b4223bea8e99cb2fe0a8afd)
This commit is contained in:
Rasmus Munk Larsen 2019-08-08 16:27:32 -07:00 committed by David Tellenbach
parent a36d19c4fc
commit 77dc6dbb44
1 changed files with 70 additions and 1 deletions
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71
Eigen/src/Core/MathFunctions.h
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@ -461,6 +461,65 @@ struct arg_retval
typedef typename NumTraits<Scalar>::Real type;
};
/****************************************************************************
* Implementation of expm1 *
****************************************************************************/
// This implementation is based on GSL Math's expm1.
namespace std_fallback {
// fallback expm1 implementation in case there is no expm1(Scalar) function in namespace of Scalar,
// or that there is no suitable std::expm1 function available. Implementation
// attributed to Kahan. See: http://www.plunk.org/~hatch/rightway.php.
template<typename Scalar>
EIGEN_DEVICE_FUNC inline Scalar expm1(const Scalar& x) {
EIGEN_STATIC_ASSERT_NON_INTEGER(Scalar)
typedef typename NumTraits<Scalar>::Real RealScalar;
EIGEN_USING_STD_MATH(exp);
Scalar u = exp(x);
if (numext::equal_strict(u, Scalar(1))) {
return x;
}
Scalar um1 = u - RealScalar(1);
if (numext::equal_strict(um1, Scalar(-1))) {
return RealScalar(-1);
}
EIGEN_USING_STD_MATH(log);
return (u - RealScalar(1)) * x / log(u);
}
}
template<typename Scalar>
struct expm1_impl {
EIGEN_DEVICE_FUNC static inline Scalar run(const Scalar& x)
{
EIGEN_STATIC_ASSERT_NON_INTEGER(Scalar)
#if EIGEN_HAS_CXX11_MATH
using std::expm1;
#else
using std_fallback::expm1;
#endif
return expm1(x);
}
};
// Specialization for complex types that are not supported by std::expm1.
template <typename RealScalar>
struct expm1_impl<std::complex<RealScalar> > {
EIGEN_DEVICE_FUNC static inline std::complex<RealScalar> run(
const std::complex<RealScalar>& x) {
EIGEN_STATIC_ASSERT_NON_INTEGER(RealScalar)
return std_fallback::expm1(x);
}
};
template<typename Scalar>
struct expm1_retval
{
typedef Scalar type;
};
/****************************************************************************
* Implementation of log1p *
****************************************************************************/
@ -485,12 +544,22 @@ struct log1p_impl {
EIGEN_STATIC_ASSERT_NON_INTEGER(Scalar)
#if EIGEN_HAS_CXX11_MATH
using std::log1p;
#endif
#else
using std_fallback::log1p;
#endif
return log1p(x);
}
};
// Specialization for complex types that are not supported by std::log1p.
template <typename RealScalar>
struct log1p_impl<std::complex<RealScalar> > {
EIGEN_DEVICE_FUNC static inline std::complex<RealScalar> run(
const std::complex<RealScalar>& x) {
EIGEN_STATIC_ASSERT_NON_INTEGER(RealScalar)
return std_fallback::log1p(x);
}
};
template<typename Scalar>
struct log1p_retval