OpenXM_contrib/gmp/mpz/ui_pow_ui.c - diff

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Diff for /OpenXM_contrib/gmp/mpz/Attic/ui_pow_ui.c between version 1.1.1.1 and 1.1.1.2

version 1.1.1.1, 2000/01/10 15:35:27

version 1.1.1.2, 2000/09/09 14:13:00

Line 1

/* mpz_ui_pow_ui(res, base, exp) -- Set RES to BASE**EXP.

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 the GNU Library General Public License as published by

it under the terms of the GNU Lesser General Public License as published by

the Free Software Foundation; either version 2 of the License, or (at your

the Free Software Foundation; either version 2.1 of the License, or (at your

option) any later version.

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 Library General Public

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 Library General Public License

You should have received a copy of the GNU Lesser General Public License

along with the GNU MP Library; see the file COPYING.LIB. If not, write to

the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,

MA 02111-1307, USA. */

Line 23 MA 02111-1307, USA. */

Line 24 MA 02111-1307, USA. */

#include "gmp-impl.h"

#include "longlong.h"

static void mpz_pow2 _PROTO ((mpz_ptr r, mp_limb_t blimb, unsigned long int e, mp_limb_t rl));

void

#if __STDC__

mpz_ui_pow_ui (mpz_ptr r, unsigned long int b, unsigned long int e)

Line 33 mpz_ui_pow_ui (r, b, e)

Line 37 mpz_ui_pow_ui (r, b, e)

unsigned long int e;

#endif

{

mp_ptr rp, tp, xp;

mp_size_t rsize;

int cnt, i;

mp_limb_t blimb = b;

TMP_DECL (marker);

mp_limb_t rl;

/* Single out cases that give result == 0 or 1. These tests are here

to simplify the general code below, not to optimize. */

if (e == 0)

{

/* For x^0 we return 1, even if x is 0. */

r->_mp_d[0] = 1;

r->_mp_size = 1;

return;

}

if (blimb == 0)

/* Compute b^e as (b^n)^(e div n) * b^(e mod n), where n is chosen such that

the latter factor is the largest number small enough to fit in a limb. */

rl = 1;

while (e != 0 && blimb < ((mp_limb_t) 1 << BITS_PER_MP_LIMB/2))

{

r->_mp_size = 0;

if ((e & 1) != 0)

return;

rl = rl * blimb;

blimb = blimb * blimb;

e = e >> 1;

}

if (blimb < 0x100)

/* rl is now b^(e mod n). (I.e., the latter factor above.) */

if (e == 0)

{

/* Estimate space requirements accurately. Using the code from the

r->_mp_d[0] = rl;

`else' path would over-estimate space requirements wildly. */

r->_mp_size = rl != 0;

float lb = __mp_bases[blimb].chars_per_bit_exactly;

return;

rsize = 2 + ((mp_size_t) (e / lb) / BITS_PER_MP_LIMB);

}

else

{

/* Over-estimate space requirements somewhat. */

count_leading_zeros (cnt, blimb);

rsize = e - cnt * e / BITS_PER_MP_LIMB + 1;

}

mpz_pow2 (r, blimb, e, rl);

}

/* Multi-precision part of expontialization code. */

static void

#if __STDC__

mpz_pow2 (mpz_ptr r, mp_limb_t blimb, unsigned long int e, mp_limb_t rl)

#else

mpz_pow2 (r, blimb, e, rl)

mpz_ptr r;

mp_limb_t blimb;

unsigned long int e;

mp_limb_t rl;

#endif

{

mp_ptr rp, tp;

mp_size_t ralloc, rsize;

int cnt, i;

TMP_DECL (marker);

TMP_MARK (marker);

/* The two areas are used to alternatingly hold the input and recieve the

/* Over-estimate temporary space requirements somewhat. */

product for mpn_mul. (This scheme is used to fulfill the requirements

count_leading_zeros (cnt, blimb);

of mpn_mul; that the product space may not be the same as any of the

ralloc = e - cnt * e / BITS_PER_MP_LIMB + 1;

input operands.) */

rp = (mp_ptr) TMP_ALLOC (rsize * BYTES_PER_MP_LIMB);

tp = (mp_ptr) TMP_ALLOC (rsize * BYTES_PER_MP_LIMB);

/* The two areas are used to alternatingly hold the input and receive the

product for mpn_mul. (Needed since mpn_mul_n requires that the product

is distinct from either input operand.) */

rp = (mp_ptr) TMP_ALLOC (ralloc * BYTES_PER_MP_LIMB);

tp = (mp_ptr) TMP_ALLOC (ralloc * BYTES_PER_MP_LIMB);

rp[0] = blimb;

rsize = 1;

count_leading_zeros (cnt, e);

for (i = BITS_PER_MP_LIMB - cnt - 2; i >= 0; i--)

{

mpn_mul_n (tp, rp, rp, rsize);

rsize = 2 * rsize;

rsize -= tp[rsize - 1] == 0;

xp = tp; tp = rp; rp = xp;

MP_PTR_SWAP (rp, tp);

if ((e & ((mp_limb_t) 1 << i)) != 0)

{

mp_limb_t cy;

cy = mpn_mul_1 (tp, rp, rsize, blimb);

cy = mpn_mul_1 (rp, rp, rsize, blimb);

if (cy != 0)

rp[rsize] = cy;

{

rsize += cy != 0;

tp[rsize] = cy;

rsize++;

}

xp = tp; tp = rp; rp = xp;

}

/* Now then we know the exact space requirements, reallocate if

/* We will need rsize or rsize+1 limbs for the result. */

necessary. */

if (r->_mp_alloc <= rsize)

if (r->_mp_alloc < rsize)

_mpz_realloc (r, rsize + 1);

_mpz_realloc (r, rsize);

MPN_COPY (r->_mp_d, rp, rsize);

/* Multiply the two factors (in rp,rsize and rl) and put the final result

in place. */

{

mp_limb_t cy;

cy = mpn_mul_1 (r->_mp_d, rp, rsize, rl);

(r->_mp_d)[rsize] = cy;

rsize += cy != 0;

}

r->_mp_size = rsize;

TMP_FREE (marker);

}

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