1 /* mpn_add_n_sub_n -- Add and Subtract two limb vectors of equal, non-zero length.
2
3 THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY
4 SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
5 GUARANTEED THAT IT'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
6
7 Copyright 1999-2001, 2006 Free Software Foundation, Inc.
8
9 This file is part of the GNU MP Library.
10
11 The GNU MP Library is free software; you can redistribute it and/or modify
12 it under the terms of either:
13
14 * the GNU Lesser General Public License as published by the Free
15 Software Foundation; either version 3 of the License, or (at your
16 option) any later version.
17
18 or
19
20 * the GNU General Public License as published by the Free Software
21 Foundation; either version 2 of the License, or (at your option) any
22 later version.
23
24 or both in parallel, as here.
25
26 The GNU MP Library is distributed in the hope that it will be useful, but
27 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
28 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
29 for more details.
30
31 You should have received copies of the GNU General Public License and the
32 GNU Lesser General Public License along with the GNU MP Library. If not,
33 see https://www.gnu.org/licenses/. */
34
35 #include "gmp-impl.h"
36
37 #ifndef L1_CACHE_SIZE
38 #define L1_CACHE_SIZE 8192 /* only 68040 has less than this */
39 #endif
40
41 #define PART_SIZE (L1_CACHE_SIZE / GMP_LIMB_BYTES / 6)
42
43
44 /* mpn_add_n_sub_n.
45 r1[] = s1[] + s2[]
46 r2[] = s1[] - s2[]
47 All operands have n limbs.
48 In-place operations allowed. */
49 mp_limb_t
50 mpn_add_n_sub_n (mp_ptr r1p, mp_ptr r2p, mp_srcptr s1p, mp_srcptr s2p, mp_size_t n)
51 {
52 mp_limb_t acyn, acyo; /* carry for add */
53 mp_limb_t scyn, scyo; /* carry for subtract */
54 mp_size_t off; /* offset in operands */
55 mp_size_t this_n; /* size of current chunk */
56
57 /* We alternatingly add and subtract in chunks that fit into the (L1)
58 cache. Since the chunks are several hundred limbs, the function call
59 overhead is insignificant, but we get much better locality. */
60
61 /* We have three variant of the inner loop, the proper loop is chosen
62 depending on whether r1 or r2 are the same operand as s1 or s2. */
63
64 if (r1p != s1p && r1p != s2p)
65 {
66 /* r1 is not identical to either input operand. We can therefore write
67 to r1 directly, without using temporary storage. */
68 acyo = 0;
69 scyo = 0;
70 for (off = 0; off < n; off += PART_SIZE)
71 {
72 this_n = MIN (n - off, PART_SIZE);
73 #if HAVE_NATIVE_mpn_add_nc
74 acyo = mpn_add_nc (r1p + off, s1p + off, s2p + off, this_n, acyo);
75 #else
76 acyn = mpn_add_n (r1p + off, s1p + off, s2p + off, this_n);
77 acyo = acyn + mpn_add_1 (r1p + off, r1p + off, this_n, acyo);
78 #endif
79 #if HAVE_NATIVE_mpn_sub_nc
80 scyo = mpn_sub_nc (r2p + off, s1p + off, s2p + off, this_n, scyo);
81 #else
82 scyn = mpn_sub_n (r2p + off, s1p + off, s2p + off, this_n);
83 scyo = scyn + mpn_sub_1 (r2p + off, r2p + off, this_n, scyo);
84 #endif
85 }
86 }
87 else if (r2p != s1p && r2p != s2p)
88 {
89 /* r2 is not identical to either input operand. We can therefore write
90 to r2 directly, without using temporary storage. */
91 acyo = 0;
92 scyo = 0;
93 for (off = 0; off < n; off += PART_SIZE)
94 {
95 this_n = MIN (n - off, PART_SIZE);
96 #if HAVE_NATIVE_mpn_sub_nc
97 scyo = mpn_sub_nc (r2p + off, s1p + off, s2p + off, this_n, scyo);
98 #else
99 scyn = mpn_sub_n (r2p + off, s1p + off, s2p + off, this_n);
100 scyo = scyn + mpn_sub_1 (r2p + off, r2p + off, this_n, scyo);
101 #endif
102 #if HAVE_NATIVE_mpn_add_nc
103 acyo = mpn_add_nc (r1p + off, s1p + off, s2p + off, this_n, acyo);
104 #else
105 acyn = mpn_add_n (r1p + off, s1p + off, s2p + off, this_n);
106 acyo = acyn + mpn_add_1 (r1p + off, r1p + off, this_n, acyo);
107 #endif
108 }
109 }
110 else
111 {
112 /* r1 and r2 are identical to s1 and s2 (r1==s1 and r2==s2 or vice versa)
113 Need temporary storage. */
114 mp_limb_t tp[PART_SIZE];
115 acyo = 0;
116 scyo = 0;
117 for (off = 0; off < n; off += PART_SIZE)
118 {
119 this_n = MIN (n - off, PART_SIZE);
120 #if HAVE_NATIVE_mpn_add_nc
121 acyo = mpn_add_nc (tp, s1p + off, s2p + off, this_n, acyo);
122 #else
123 acyn = mpn_add_n (tp, s1p + off, s2p + off, this_n);
124 acyo = acyn + mpn_add_1 (tp, tp, this_n, acyo);
125 #endif
126 #if HAVE_NATIVE_mpn_sub_nc
127 scyo = mpn_sub_nc (r2p + off, s1p + off, s2p + off, this_n, scyo);
128 #else
129 scyn = mpn_sub_n (r2p + off, s1p + off, s2p + off, this_n);
130 scyo = scyn + mpn_sub_1 (r2p + off, r2p + off, this_n, scyo);
131 #endif
132 MPN_COPY (r1p + off, tp, this_n);
133 }
134 }
135
136 return 2 * acyo + scyo;
137 }
138
139 #ifdef MAIN
140 #include <stdlib.h>
141 #include <stdio.h>
142 #include "timing.h"
143
144 long cputime ();
145
146 int
147 main (int argc, char **argv)
148 {
149 mp_ptr r1p, r2p, s1p, s2p;
150 double t;
151 mp_size_t n;
152
153 n = strtol (argv[1], 0, 0);
154
155 r1p = malloc (n * GMP_LIMB_BYTES);
156 r2p = malloc (n * GMP_LIMB_BYTES);
157 s1p = malloc (n * GMP_LIMB_BYTES);
158 s2p = malloc (n * GMP_LIMB_BYTES);
159 TIME (t,(mpn_add_n(r1p,s1p,s2p,n),mpn_sub_n(r1p,s1p,s2p,n)));
160 printf (" separate add and sub: %.3f\n", t);
161 TIME (t,mpn_add_n_sub_n(r1p,r2p,s1p,s2p,n));
162 printf ("combined addsub separate variables: %.3f\n", t);
163 TIME (t,mpn_add_n_sub_n(r1p,r2p,r1p,s2p,n));
164 printf (" combined addsub r1 overlap: %.3f\n", t);
165 TIME (t,mpn_add_n_sub_n(r1p,r2p,r1p,s2p,n));
166 printf (" combined addsub r2 overlap: %.3f\n", t);
167 TIME (t,mpn_add_n_sub_n(r1p,r2p,r1p,r2p,n));
168 printf (" combined addsub in-place: %.3f\n", t);
169
170 return 0;
171 }
172 #endif