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
/*
Copyright (C) 2014 Alex J. Best
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 "fmpz.h"
#include "fmpz_mat.h"
/* sets a to gcd(a,b) and b to lcm(a,b) using temporary fmpz_t t */
static void _gcdlcm(fmpz_t t, fmpz_t a, fmpz_t b)
{
if (fmpz_equal(a, b)) return;
fmpz_gcd(t, a, b);
fmpz_divexact(b, b, t);
fmpz_mul(b, b, a);
fmpz_set(a, t);
}
void fmpz_mat_snf_diagonal(fmpz_mat_t S, const fmpz_mat_t A)
{
fmpz_t t;
slong i, j, n = FLINT_MIN(A->r, A->c);
fmpz_init(t);
fmpz_mat_set(S, A);
for (i = 0; i < n; i++)
fmpz_abs(fmpz_mat_entry(S, i, i), fmpz_mat_entry(S, i, i));
for (j = n - 1; j >= 0; j--)
{
for (i = 0; i < j; i++)
{
_gcdlcm(t, fmpz_mat_entry(S, i, i),
fmpz_mat_entry(S, i + 1, i + 1));
}
}
fmpz_clear(t);
}