mirror of
https://github.com/vale981/arb
synced 2025-03-06 09:51:39 -05:00
fa1a85b746
- try to handle even and odd components the same way in the dirichlet group - switch from phi_q_odd to smaller expo = exponent of the group all character orders divide this number, and a character of that order exists - use conrey logarithm to reuse log and to loop efficiently over the group (see the diff on l.c, only 1 log in computed instead of 2 * q) - NOT TESTED, for the moment it just compiles, I know some errors (e.g. the FIXME in group_init.c : the generators have to be lifted mod q) this commit is just a proof of concept.
91 lines
2.5 KiB
C
91 lines
2.5 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) 2015 Jonathan Bober
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Copyright (C) 2016 Fredrik Johansson
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******************************************************************************/
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#include "acb_dirichlet.h"
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/* todo: modular arithmetic
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discrete log can be computed along exponents or using p-adic log
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*/
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void
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acb_conrey_init(acb_conrey_t x, const acb_dirichlet_group_t G) {
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x->log = flint_malloc(G->num * sizeof(ulong));
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}
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void
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acb_conrey_one(acb_conrey_t x, const acb_dirichlet_group_t G) {
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ulong k;
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for (k = 0; k < G->num ; k++)
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x->log[k] = 0;
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x->n = 1;
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}
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void
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acb_conrey_clear(acb_conrey_t x) {
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flint_free(x->log);
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}
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/* TODO: use precomputations in G if present */
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void
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acb_conrey_log(acb_conrey_t x, const acb_dirichlet_group_t G, ulong m)
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{
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ulong k, pk, gk;
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/* even part */
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if (G->neven >= 1)
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x->log[0] = (m % 4 == 3);
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if (G->neven == 2)
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{
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ulong q_even = G->q_even;
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ulong g2 = 5;
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ulong m2 = (m % 4 == 3) ? n_negmod(m, q_even) : m % q_even;
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x->log[1] = n_discrete_log_bsgs(m2, g2, q_even);
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}
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/* odd part */
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for (k = G->neven; k < G->num; k++)
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{
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pk = n_pow(G->primes[k], G->exponents[k]);
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gk = G->generators[k] % pk;
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x->log[k] = n_discrete_log_bsgs(m % pk, gk, pk);
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}
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/* keep value m */
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x->n = m;
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}
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int
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acb_conrey_next(acb_conrey_t x, const acb_dirichlet_group_t G)
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{
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/* update index */
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ulong k;
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for (k=0; k < G->num ; k++)
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{
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x->n = x->n * G->generators[k];
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if(x->log[k]++ < G->phi[k])
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break;
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x->log[k] = 0;
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}
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/* return last index modified */
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return k;
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}
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