arb/dlog/modpe.c

52 lines
1.7 KiB
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) 2016 Pascal Molin
******************************************************************************/
#include "dlog.h"
ulong
dlog_modpe(const dlog_modpe_t t, ulong b)
{
ulong x;
if (t->p == 2)
return dlog_mod2e(t, b);
x = dlog_precomp(t->modp, b % t->p);
if (t->e > 1)
{
ulong b1, y;
#if 0
b1 = nmod_mul(b, nmod_pow_ui(t->inva, x, t->pe), t->pe);
y = dlog_1modpe(t->modpe.rec, b1, t->p, t->e, t->pe);
y = y % t->pe1;
x = x + (t->p - 1) * y;
#else
b1 = nmod_pow_ui(b, t->p - 1, t->pe);
y = dlog_1modpe(t->modpe, b1, t->p, t->e, t->pe);
y = y % t->pe1;
x = n_submod(x, y % (t->p - 1), t->p - 1);
x = y + t->pe1 * x;
#endif
}
return x;
}