flint-sys 0.9.0

Bindings to the FLINT C library
Documentation 
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
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134

/*
    Copyright (C) 2007, 2008 William Hart
    Copyright (C) 2011 Sebastian Pancratz
    Copyright (C) 2014 William Hart

    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 "gr_vec.h"
#include "gr_poly.h"

#define GR_VEC_NORM(status, R, lenR, sz, ctx) \
    do { \
        (void) sz; \
        (status) |= _gr_vec_normalise(&(lenR), (R), (lenR), (ctx)); \
    } while (0)

int
_gr_poly_resultant_euclidean(gr_ptr res, gr_srcptr poly1, slong len1,
                    gr_srcptr poly2, slong len2, gr_ctx_t ctx)
{
    gr_ptr u, v, r, t, w, q;
    slong l0, l1, l2;
    gr_ptr lc;
    int status = GR_SUCCESS;
    slong sz = ctx->sizeof_elem;

    if (len2 == 1)
        return _gr_poly_resultant_small(res, poly1, len1, poly2, len2, ctx);

    /* todo: we can skip the q tmp allocation when we have a dedicated rem() */
    GR_TMP_INIT_VEC(w, 4 * len1 + 1, ctx);

    q = w;
    u = GR_ENTRY(q, len1, sz);
    v = GR_ENTRY(u, len1, sz);
    r = GR_ENTRY(v, len1, sz);
    lc = GR_ENTRY(r, len1, sz);

    status |= gr_one(res, ctx);

    status |= _gr_vec_set(u, poly1, len1, ctx);
    status |= _gr_vec_set(v, poly2, len2, ctx);
    l1 = len1;
    l2 = len2;

    do
    {
        l0 = l1;
        l1 = l2;
        status |= gr_set(lc, GR_ENTRY(v, l1 - 1, sz), ctx);
        /* todo: just rem */
        status |= _gr_poly_divrem(q, r, u, l0, v, l1, ctx);

        if (status != GR_SUCCESS)
            break;

        l2 = l1 - 1;

        GR_VEC_NORM(status, r, l2, sz, ctx);

        {
            t = u;
            u = v;
            v = r;
            r = t;
        }

        if (l2 >= 1)
        {
            status |= gr_pow_ui(lc, lc, l0 - l2, ctx);
            status |= gr_mul(res, res, lc, ctx);

            if (((l0 | l1) & 1) == 0)
                status |= gr_neg(res, res, ctx);
        }
        else
        {
            if (l1 == 1)
            {
                status |= gr_pow_ui(lc, lc, l0 - 1, ctx);
                status |= gr_mul(res, res, lc, ctx);
            }
            else
            {
                status |= gr_zero(res, ctx);
            }
        }
    }
    while (l2 > 0);

    GR_TMP_CLEAR_VEC(w, 4 * len1 + 1, ctx);

    return status;
}

int gr_poly_resultant_euclidean(gr_ptr r, const gr_poly_t f,
                             const gr_poly_t g, gr_ctx_t ctx)
{
    slong len1 = f->length;
    slong len2 = g->length;
    int status = GR_SUCCESS;
    slong sz = ctx->sizeof_elem;

    if (len1 == 0 || len2 == 0)
    {
        return gr_zero(r, ctx);
    }

    if (gr_is_zero(GR_ENTRY(f->coeffs, len1 - 1, sz), ctx) != T_FALSE ||
        gr_is_zero(GR_ENTRY(g->coeffs, len2 - 1, sz), ctx) != T_FALSE)
    {
        return GR_UNABLE;
    }

    if (len1 >= len2)
    {
        status |= _gr_poly_resultant_euclidean(r, f->coeffs, len1,  g->coeffs, len2, ctx);
    }
    else
    {
        status |= _gr_poly_resultant_euclidean(r, g->coeffs, len2, f->coeffs, len1, ctx);

        if (((len1 | len2) & 1) == 0)
            status |= gr_neg(r, r, ctx);
    }

    return status;
}