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Diffstat (limited to 'Build/source/libs/mpfr/mpfr-3.1.3/src/ui_pow_ui.c')
-rw-r--r-- | Build/source/libs/mpfr/mpfr-3.1.3/src/ui_pow_ui.c | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/Build/source/libs/mpfr/mpfr-3.1.3/src/ui_pow_ui.c b/Build/source/libs/mpfr/mpfr-3.1.3/src/ui_pow_ui.c new file mode 100644 index 00000000000..eabb1fba8b8 --- /dev/null +++ b/Build/source/libs/mpfr/mpfr-3.1.3/src/ui_pow_ui.c @@ -0,0 +1,95 @@ +/* mpfr_ui_pow_ui -- compute the power beetween two machine integer + +Copyright 1999-2015 Free Software Foundation, Inc. +Contributed by the AriC and Caramel projects, INRIA. + +This file is part of the GNU MPFR Library. + +The GNU MPFR Library is free software; you can redistribute it and/or modify +it under the terms of 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. + +The GNU MPFR 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 Lesser General Public +License for more details. + +You should have received a copy of the GNU Lesser General Public License +along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see +http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., +51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ + +#include "mpfr-impl.h" + +int +mpfr_ui_pow_ui (mpfr_ptr x, unsigned long int y, unsigned long int n, + mpfr_rnd_t rnd) +{ + mpfr_exp_t err; + unsigned long m; + mpfr_t res; + mpfr_prec_t prec; + int size_n; + int inexact; + MPFR_ZIV_DECL (loop); + MPFR_SAVE_EXPO_DECL (expo); + + if (MPFR_UNLIKELY (n <= 1)) + { + if (n == 1) + return mpfr_set_ui (x, y, rnd); /* y^1 = y */ + else + return mpfr_set_ui (x, 1, rnd); /* y^0 = 1 for any y */ + } + else if (MPFR_UNLIKELY (y <= 1)) + { + if (y == 1) + return mpfr_set_ui (x, 1, rnd); /* 1^n = 1 for any n > 0 */ + else + return mpfr_set_ui (x, 0, rnd); /* 0^n = 0 for any n > 0 */ + } + + for (size_n = 0, m = n; m; size_n++, m >>= 1); + + MPFR_SAVE_EXPO_MARK (expo); + prec = MPFR_PREC (x) + 3 + size_n; + mpfr_init2 (res, prec); + + MPFR_ZIV_INIT (loop, prec); + for (;;) + { + int i = size_n; + + inexact = mpfr_set_ui (res, y, MPFR_RNDU); + err = 1; + /* now 2^(i-1) <= n < 2^i: i=1+floor(log2(n)) */ + for (i -= 2; i >= 0; i--) + { + inexact |= mpfr_mul (res, res, res, MPFR_RNDU); + err++; + if (n & (1UL << i)) + inexact |= mpfr_mul_ui (res, res, y, MPFR_RNDU); + } + /* since the loop is executed floor(log2(n)) times, + we have err = 1+floor(log2(n)). + Since prec >= MPFR_PREC(x) + 4 + floor(log2(n)), prec > err */ + err = prec - err; + + if (MPFR_LIKELY (inexact == 0 + || MPFR_CAN_ROUND (res, err, MPFR_PREC (x), rnd))) + break; + + /* Actualisation of the precision */ + MPFR_ZIV_NEXT (loop, prec); + mpfr_set_prec (res, prec); + } + MPFR_ZIV_FREE (loop); + + inexact = mpfr_set (x, res, rnd); + + mpfr_clear (res); + + MPFR_SAVE_EXPO_FREE (expo); + return mpfr_check_range (x, inexact, rnd); +} |