arb/acb_dirichlet/conrey_log.c

/*=============================================================================

    This file is part of ARB.

    ARB is free software; you can redistribute it and/or modify
    it under the terms of 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.

    ARB 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 a copy of the GNU General Public License
    along with ARB; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

=============================================================================*/
/******************************************************************************

    Copyright (C) 2015 Jonathan Bober
    Copyright (C) 2016 Fredrik Johansson
    Copyright (C) 2016 Pascal Molin

******************************************************************************/

#include "acb_dirichlet.h"

/* TODO: use precomputations in G if present */
/* assume m is invertible */
void
acb_dirichlet_conrey_log(acb_dirichlet_conrey_t x, const acb_dirichlet_group_t G, ulong m)
{
    ulong k, pk, gk;
    /* even part */
    if (G->neven >= 1)
    {
      x->log[0] = (m % 4 == 3);
      if (G->neven == 2)
      {
        ulong m2 = (x->log[0]) ? -m % G->q_even : m % G->q_even;
        if (G->dlog == NULL)
            x->log[1] = n_discrete_log_bsgs(m2, 5, G->q_even);
        else
            x->log[1] = dlog_precomp(G->dlog[1], m2);
      }
    }
    /* odd part */
    if (G->dlog == NULL)
    {
        for (k = G->neven; k < G->num; k++)
        {
            pk = G->primepowers[k];
            gk = G->generators[k] % pk;
            x->log[k] = n_discrete_log_bsgs(m % pk, gk, pk);
        }
    }
    else
    {
        for (k = G->neven; k < G->num; k++)
            x->log[k] = dlog_precomp(G->dlog[k], m % G->primepowers[k]);
    }
    /* keep value m */
    x->n = m;
}