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
/*
Copyright (C) 2010 Fredrik Johansson
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 "ulong_extras.h"
#include "nmod_mat.h"
int nmod_mat_inv(nmod_mat_t B, const nmod_mat_t A)
{
nmod_mat_t I;
slong i, dim;
int result;
dim = A->r;
switch (dim)
{
case 0:
result = 1;
break;
case 1:
if (nmod_mat_entry(A, 0, 0) == UWORD(0))
{
result = 0;
}
else
{
nmod_mat_entry(B, 0, 0) =
n_invmod(nmod_mat_entry(A, 0, 0), B->mod.n);
result = 1;
}
break;
default:
nmod_mat_init(I, dim, dim, B->mod.n);
for (i = 0; i < dim; i++)
nmod_mat_entry(I, i, i) = UWORD(1);
result = nmod_mat_solve(B, A, I);
nmod_mat_clear(I);
}
return result;
}