1 /* mpz_prodlimbs(RESULT, V, LEN) -- Set RESULT to V[0]*V[1]*...*V[LEN-1].
2
3 Contributed to the GNU project by Marco Bodrato.
4
5 THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.
6 IT IS ONLY SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.
7 IN FACT, IT IS ALMOST GUARANTEED THAT IT WILL CHANGE OR
8 DISAPPEAR IN A FUTURE GNU MP RELEASE.
9
10 Copyright 2010-2012 Free Software Foundation, Inc.
11
12 This file is part of the GNU MP Library.
13
14 The GNU MP Library is free software; you can redistribute it and/or modify
15 it under the terms of either:
16
17 * the GNU Lesser General Public License as published by the Free
18 Software Foundation; either version 3 of the License, or (at your
19 option) any later version.
20
21 or
22
23 * the GNU General Public License as published by the Free Software
24 Foundation; either version 2 of the License, or (at your option) any
25 later version.
26
27 or both in parallel, as here.
28
29 The GNU MP Library is distributed in the hope that it will be useful, but
30 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
31 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
32 for more details.
33
34 You should have received copies of the GNU General Public License and the
35 GNU Lesser General Public License along with the GNU MP Library. If not,
36 see https://www.gnu.org/licenses/. */
37
38 #include "gmp-impl.h"
39
40 /*********************************************************/
41 /* Section list-prod: product of a list -> mpz_t */
42 /*********************************************************/
43
44 /* FIXME: should be tuned */
45 #ifndef RECURSIVE_PROD_THRESHOLD
46 #define RECURSIVE_PROD_THRESHOLD (MUL_TOOM22_THRESHOLD)
47 #endif
48
49 /* Computes the product of the j>1 limbs pointed by factors, puts the
50 * result in x. It assumes that all limbs are non-zero. Above
51 * Karatsuba's threshold it uses a binary splitting strategy, to gain
52 * speed by the asymptotically fast multiplication algorithms.
53 *
54 * The list in {factors, j} is overwritten.
55 * Returns the size of the result
56 */
57
58 mp_size_t
mpz_prodlimbs(mpz_ptr x,mp_ptr factors,mp_size_t j)59 mpz_prodlimbs (mpz_ptr x, mp_ptr factors, mp_size_t j)
60 {
61 mp_limb_t cy;
62 mp_size_t size, i;
63 mp_ptr prod;
64
65 ASSERT (j > 1);
66 ASSERT (RECURSIVE_PROD_THRESHOLD > 3);
67
68 if (BELOW_THRESHOLD (j, RECURSIVE_PROD_THRESHOLD)) {
69 j--;
70 size = 1;
71
72 for (i = 1; i < j; i++)
73 {
74 cy = mpn_mul_1 (factors, factors, size, factors[i]);
75 factors[size] = cy;
76 size += cy != 0;
77 };
78
79 prod = MPZ_NEWALLOC (x, size + 1);
80
81 cy = mpn_mul_1 (prod, factors, size, factors[i]);
82 prod[size] = cy;
83 return SIZ (x) = size + (cy != 0);
84 } else {
85 mpz_t x1, x2;
86 TMP_DECL;
87
88 i = j >> 1;
89 j -= i;
90 TMP_MARK;
91
92 MPZ_TMP_INIT (x2, j);
93
94 PTR (x1) = factors + i;
95 ALLOC (x1) = j;
96 j = mpz_prodlimbs (x2, factors + i, j);
97 i = mpz_prodlimbs (x1, factors, i);
98 size = i + j;
99 prod = MPZ_NEWALLOC (x, size);
100 if (i >= j)
101 cy = mpn_mul (prod, PTR(x1), i, PTR(x2), j);
102 else
103 cy = mpn_mul (prod, PTR(x2), j, PTR(x1), i);
104 TMP_FREE;
105
106 return SIZ (x) = size - (cy == 0);
107 }
108 }
109