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
59
60
61
62
63
64
65
66
67
68
69
70
71
/*
Copyright (C) 2011, 2012 Sebastian Pancratz
Copyright (C) 2012 Andres Goens
Copyright (C) 2013 Mike Hansen
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_vec.h"
#include "nmod_poly.h"
#include "fq_nmod.h"
static void _fq_nmod_inv(ulong *rop, const ulong *op, slong len,
const fq_nmod_ctx_t ctx)
{
const slong d = fq_nmod_ctx_degree(ctx);
if (len == 1)
{
rop[0] = n_invmod(op[0], ctx->mod.n);
_nmod_vec_zero(rop + 1, d - 1);
}
else
{
_nmod_poly_invmod(rop, op, len, ctx->modulus->coeffs, d + 1, ctx->mod);
}
}
void fq_nmod_inv(fq_nmod_t rop, const fq_nmod_t op, const fq_nmod_ctx_t ctx)
{
if (fq_nmod_is_zero(op, ctx))
{
flint_throw(FLINT_ERROR, "Exception (fq_nmod_inv). Zero is not invertible.\n");
}
else
{
const slong d = fq_nmod_ctx_degree(ctx);
ulong *t;
if (rop == op)
{
t = _nmod_vec_init(d);
}
else
{
nmod_poly_fit_length(rop, d);
t = rop->coeffs;
}
_fq_nmod_inv(t, op->coeffs, op->length, ctx);
if (rop == op)
{
_nmod_vec_clear(rop->coeffs);
rop->coeffs = t;
rop->alloc = d;
rop->length = d;
}
else
{
_nmod_poly_set_length(rop, d);
}
_nmod_poly_normalise(rop);
}
}