diff options
author | Thomas Voss <mail@thomasvoss.com> | 2024-06-21 23:36:36 +0200 |
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committer | Thomas Voss <mail@thomasvoss.com> | 2024-06-21 23:42:26 +0200 |
commit | a89a14ef5da44684a16b204e7a70460cc8c4922a (patch) | |
tree | b23b4c6b155977909ef508fdae2f48d33d802813 /vendor/gmp-6.3.0/mpf/pow_ui.c | |
parent | 1db63fcedab0b288820d66e100b1877b1a5a8851 (diff) |
Basic constant folding implementation
Diffstat (limited to 'vendor/gmp-6.3.0/mpf/pow_ui.c')
-rw-r--r-- | vendor/gmp-6.3.0/mpf/pow_ui.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/vendor/gmp-6.3.0/mpf/pow_ui.c b/vendor/gmp-6.3.0/mpf/pow_ui.c new file mode 100644 index 0000000..8d54dc0 --- /dev/null +++ b/vendor/gmp-6.3.0/mpf/pow_ui.c @@ -0,0 +1,83 @@ +/* mpf_pow_ui -- Compute b^e. + +Copyright 1998, 1999, 2001, 2012, 2015 Free Software Foundation, Inc. + +This file is part of the GNU MP Library. + +The GNU MP Library is free software; you can redistribute it and/or modify +it under the terms of either: + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your + option) any later version. + +or + + * the GNU General Public License as published by the Free Software + Foundation; either version 2 of the License, or (at your option) any + later version. + +or both in parallel, as here. + +The GNU MP Library is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received copies of the GNU General Public License and the +GNU Lesser General Public License along with the GNU MP Library. If not, +see https://www.gnu.org/licenses/. */ + +#include "gmp-impl.h" +#include "longlong.h" + +/* This uses a plain right-to-left square-and-multiply algorithm. + + FIXME: When popcount(e) is not too small, it would probably speed things up + to use a k-ary sliding window algorithm. */ + +void +mpf_pow_ui (mpf_ptr r, mpf_srcptr b, unsigned long int e) +{ + mpf_t t; + int cnt; + + if (e <= 1) + { + if (e == 0) + mpf_set_ui (r, 1); + else + mpf_set (r, b); + return; + } + + count_leading_zeros (cnt, (mp_limb_t) e); + cnt = GMP_LIMB_BITS - 1 - cnt; + + /* Increase computation precision as a function of the exponent. Adding + log2(popcount(e) + log2(e)) bits should be sufficient, but we add log2(e), + i.e. much more. With mpf's rounding of precision to whole limbs, this + will be excessive only when limbs are artificially small. */ + mpf_init2 (t, mpf_get_prec (r) + cnt); + + mpf_set (t, b); /* consume most significant bit */ + while (--cnt > 0) + { + mpf_mul (t, t, t); + if ((e >> cnt) & 1) + mpf_mul (t, t, b); + } + + /* Do the last iteration specially in order to save a copy operation. */ + if (e & 1) + { + mpf_mul (t, t, t); + mpf_mul (r, t, b); + } + else + { + mpf_mul (r, t, t); + } + + mpf_clear (t); +} |