devtools/eigen
1
0
Fork 0
mirror of https://gitlab.com/libeigen/eigen.git synced 2026-04-10 11:34:33 +08:00
Code Issues Packages Projects Releases Wiki Activity

Add exp2() as a packet op and array method.

Browse Source
This commit is contained in:
Rasmus Munk Larsen
2024-10-22 22:09:34 +00:00
parent 4e5136d239
commit 3f067c4850
15 changed files with 193 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files

38
Eigen/src/Core/arch/Default/GenericPacketMathFunctions.h
View File

@@ -469,7 +469,7 @@ EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS Packet plog2_double(const Pa
See: http://www.plunk.org/~hatch/rightway.php
*/
template <typename Packet>
Packet generic_plog1p(const Packet& x) {
EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS Packet generic_log1p(const Packet& x) {
typedef typename unpacket_traits<Packet>::type ScalarType;
const Packet one = pset1<Packet>(ScalarType(1));
Packet xp1 = padd(x, one);
@@ -484,7 +484,7 @@ Packet generic_plog1p(const Packet& x) {
See: http://www.plunk.org/~hatch/rightway.php
*/
template <typename Packet>
Packet generic_expm1(const Packet& x) {
EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS Packet generic_expm1(const Packet& x) {
typedef typename unpacket_traits<Packet>::type ScalarType;
const Packet one = pset1<Packet>(ScalarType(1));
const Packet neg_one = pset1<Packet>(ScalarType(-1));
@@ -1109,7 +1109,7 @@ EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS Packet patan_reduced<float>:
}
template <typename Packet>
EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS Packet generic_patan(const Packet& x_in) {
EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS Packet generic_atan(const Packet& x_in) {
typedef typename unpacket_traits<Packet>::type Scalar;
constexpr Scalar kPiOverTwo = static_cast<Scalar>(EIGEN_PI / 2);
@@ -1973,13 +1973,13 @@ struct accurate_log2<double> {
}
};
// This function computes exp2(x) (i.e. 2**x).
// This function accurately computes exp2(x) for x in [-0.5:0.5], which is
// needed in pow(x,y).
template <typename Scalar>
struct fast_accurate_exp2 {
template <typename Packet>
EIGEN_STRONG_INLINE Packet operator()(const Packet& x) {
// TODO(rmlarsen): Add a pexp2 packetop.
return pexp(pmul(pset1<Packet>(Scalar(EIGEN_LN2)), x));
return generic_exp2(x);
}
};
@@ -2464,6 +2464,32 @@ struct unary_pow_impl<Packet, ScalarExponent, true, true, false> {
}
};
// This function computes exp2(x) = exp(ln(2) * x).
// To improve accuracy, the product ln(2)*x is computed using the twoprod
// algorithm, such that ln(2) * x = p_hi + p_lo holds exactly. Then exp2(x) is
// computed as exp2(x) = exp(p_hi) * exp(p_lo) ~= exp(p_hi) * (1 + p_lo). This
// correction step this reduces the maximum absolute error as follows:
//
// type | max error (simple product) | max error (twoprod) |
// -----------------------------------------------------------
// float | 35 ulps | 4 ulps |
// double | 363 ulps | 110 ulps |
//
template <typename Packet>
EIGEN_DEFINE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS Packet generic_exp2(const Packet& _x) {
typedef typename unpacket_traits<Packet>::type Scalar;
constexpr int max_exponent = std::numeric_limits<Scalar>::max_exponent;
constexpr int digits = std::numeric_limits<Scalar>::digits;
constexpr Scalar max_cap = Scalar(max_exponent + 1);
constexpr Scalar min_cap = -Scalar(max_exponent + digits - 1);
Packet x = pmax(pmin(_x, pset1<Packet>(max_cap)), pset1<Packet>(min_cap));
Packet p_hi, p_lo;
twoprod(pset1<Packet>(Scalar(EIGEN_LN2)), x, p_hi, p_lo);
Packet exp2_hi = pexp(p_hi);
Packet exp2_lo = padd(pset1<Packet>(Scalar(1)), p_lo);
return pmul(exp2_hi, exp2_lo);
}
template <typename Packet>
EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet generic_rint(const Packet& a) {
using Scalar = typename unpacket_traits<Packet>::type;