93 lines
2.2 KiB
C++
93 lines
2.2 KiB
C++
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#pragma once
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namespace {
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// adapted from GNU Scientific Library: https://git.savannah.gnu.org/cgit/gsl.git/tree/sys/pow_int.c
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// need to make sure `exp >= 0` before calling this function
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template<typename T>
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T __nac3_int_exp_impl(T base, T exp) {
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T res = 1;
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/* repeated squaring method */
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do {
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if (exp & 1) {
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res *= base; /* for n odd */
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}
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exp >>= 1;
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base *= base;
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} while (exp);
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return res;
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}
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} // namespace
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#define DEF_nac3_int_exp_(T) \
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T __nac3_int_exp_##T(T base, T exp) { \
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return __nac3_int_exp_impl(base, exp); \
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}
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extern "C" {
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// Putting semicolons here to make clang-format not reformat this into
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// a stair shape.
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DEF_nac3_int_exp_(int32_t);
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DEF_nac3_int_exp_(int64_t);
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DEF_nac3_int_exp_(uint32_t);
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DEF_nac3_int_exp_(uint64_t);
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int32_t __nac3_isinf(double x) {
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return __builtin_isinf(x);
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}
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int32_t __nac3_isnan(double x) {
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return __builtin_isnan(x);
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}
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double tgamma(double arg);
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double __nac3_gamma(double z) {
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// Handling for denormals
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// | x | Python gamma(x) | C tgamma(x) |
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// --- | ----------------- | --------------- | ----------- |
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// (1) | nan | nan | nan |
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// (2) | -inf | -inf | inf |
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// (3) | inf | inf | inf |
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// (4) | 0.0 | inf | inf |
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// (5) | {-1.0, -2.0, ...} | inf | nan |
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// (1)-(3)
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if (__builtin_isinf(z) || __builtin_isnan(z)) {
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return z;
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}
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double v = tgamma(z);
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// (4)-(5)
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return __builtin_isinf(v) || __builtin_isnan(v) ? __builtin_inf() : v;
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}
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double lgamma(double arg);
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double __nac3_gammaln(double x) {
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// libm's handling of value overflows differs from scipy:
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// - scipy: gammaln(-inf) -> -inf
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// - libm : lgamma(-inf) -> inf
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if (__builtin_isinf(x)) {
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return x;
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}
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return lgamma(x);
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}
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double j0(double x);
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double __nac3_j0(double x) {
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// libm's handling of value overflows differs from scipy:
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// - scipy: j0(inf) -> nan
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// - libm : j0(inf) -> 0.0
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if (__builtin_isinf(x)) {
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return __builtin_nan("");
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}
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return j0(x);
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}
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}
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