1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
/*
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"
ulong
dlog_crt_init(dlog_crt_t t, ulong a, ulong mod, ulong n, ulong num)
{
int k;
n_factor_t fac;
ulong * M, * u;
ulong cost = 0;
n_factor_init(&fac);
n_factor(&fac, n, 1);
t->num = fac.num;
nmod_init(&t->mod,mod);
nmod_init(&t->n, n);
M = t->expo = flint_malloc(t->num * sizeof(ulong));
u = t->crt_coeffs = flint_malloc(t->num * sizeof(ulong));
t->pre = flint_malloc(t->num * sizeof(dlog_precomp_struct));
for (k = 0; k < t->num; k++)
{
ulong p, e, mk;
p = fac.p[k];
e = fac.exp[k];
if (0 && mod % p == 0)
{
flint_throw(FLINT_ERROR, "dlog_crt_init: modulus must be prime to order.\n");
}
mk = n_pow(p, e);
M[k] = n / mk;
u[k] = nmod_mul(M[k], n_invmod(M[k] % mk, mk), t->n);
/* depends on the power */
#if 0
flint_printf("[sub-crt -- init for size %wu mod %wu]\n", mk, mod);
#endif
dlog_precomp_pe_init(t->pre + k, nmod_pow_ui(a, M[k], t->mod), mod, p, e, mk, num);
cost += t->pre[k].cost;
}
#if 0
if (cost > 500)
flint_printf("[crt init for size %wu mod %wu -> cost %wu]\n", n,mod,cost);
#endif
return cost;
}