mirror of
https://github.com/vale981/arb
synced 2025-03-05 17:31:38 -05:00
92 lines
2.6 KiB
C
92 lines
2.6 KiB
C
/*=============================================================================
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This file is part of ARB.
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ARB is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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ARB is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with ARB; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2016 Pascal Molin
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******************************************************************************/
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#include "dlog.h"
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void
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dlog_crt_init(dlog_crt_t t, ulong a, ulong mod, ulong n, ulong num)
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{
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int k;
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n_factor_t fac;
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ulong * M, * u;
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n_factor_init(&fac);
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n_factor(&fac, n, 1);
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t->num = fac.num;
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t->mod = mod;
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t->n = n;
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M = t->expo = flint_malloc(t->num * sizeof(ulong));
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u = t->crt_coeffs = flint_malloc(t->num * sizeof(ulong));
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t->pre = flint_malloc(t->num * sizeof(dlog_precomp_t));
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for (k = 0; k < t->num; k++)
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t->pre[k] = flint_malloc(sizeof(dlog_precomp_struct));
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for (k = 0; k < t->num; k++)
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{
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ulong p, e, mk;
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p = fac.p[k];
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e = fac.exp[k];
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mk = n_pow(p, e);
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M[k] = n / mk;
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u[k] = M[k] * n_invmod(M[k] % mk, mk) % n;
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/* depends on the power */
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dlog_precomp_pe_init(t->pre[k], n_powmod(a, M[k], mod), mod, p, e, mk, num);
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}
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}
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void
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dlog_crt_clear(dlog_crt_t t)
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{
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int k;
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flint_free(t->expo);
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flint_free(t->crt_coeffs);
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for (k = 0; k < t->num; k++)
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{
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dlog_precomp_clear(t->pre[k]);
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flint_free(t->pre[k]);
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}
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flint_free(t->pre);
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}
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ulong
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dlog_crt(const dlog_crt_t t, ulong b)
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{
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int k;
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ulong r = 0;
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for (k = 0; k < t->num; k++)
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{
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ulong bk, rk;
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bk = n_powmod(b, t->expo[k], t->mod);
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rk = dlog_precomp(t->pre[k], bk);
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#if 0
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flint_printf("##[crt-%d]: log(%wu)=log(%wu^%wu) = %wu [size %wu mod %wu]\n",
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k, bk, b, t->expo[k], rk, t->n/t->expo[k], t->mod);
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#endif
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r = (r + t->crt_coeffs[k] * rk) % t->n;
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}
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return r;
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}
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