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/*
Copyright (C) 2016 Pascal Molin
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "nmod.h"
#include "dlog.h"
/* todo: recursion could be made quadratic (not very useful for ulongs) */
ulong
dlog_modpe_init(dlog_modpe_t t, ulong a, ulong p, ulong e, ulong pe, ulong num)
{
ulong a1;
t->p = p;
t->e = e;
nmod_init(&t->pe, pe);
t->inva = nmod_inv(a, t->pe);
if (p == 2)
{
t->modp = NULL;
t->pe1 = (e <= 2) ? 2 : pe / 4;
t->modpe->inv1p = t->inva;
t->modpe->invloga1 = 1;
return e - 2;
}
else
{
t->modp = flint_malloc(sizeof(dlog_precomp_struct));
t->pe1 = pe / p;
dlog_precomp_n_init(t->modp, a, p, p - 1, num);
a1 = nmod_pow_ui(a, p - 1, t->pe);
dlog_1modpe_init(t->modpe, a1, p, e, t->pe);
return t->modp->cost + e;
}
}