1// +build ignore
2
3/*
4Redistribution and use in source and binary forms, with or without
5modification, are permitted provided that the following conditions are met:
6
7 * Redistributions of source code must retain the above copyright
8 notice, this list of conditions and the following disclaimer.
9
10 * Redistributions in binary form must reproduce the above copyright
11 notice, this list of conditions and the following disclaimer in the
12 documentation and/or other materials provided with the distribution.
13
14 * Neither the name of "The Computer Language Benchmarks Game" nor the
15 name of "The Computer Language Shootout Benchmarks" nor the names of
16 its contributors may be used to endorse or promote products derived
17 from this software without specific prior written permission.
18
19THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
23LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29POSSIBILITY OF SUCH DAMAGE.
30*/
31
32/*
33 * The Great Computer Language Shootout
34 * http://shootout.alioth.debian.org/
35 *
36 * contributed by Christoph Bauer
37 *
38 */
39
40#include <math.h>
41#include <stdio.h>
42#include <stdlib.h>
43
44#define pi 3.141592653589793
45#define solar_mass (4 * pi * pi)
46#define days_per_year 365.24
47
48struct planet {
49 double x, y, z;
50 double vx, vy, vz;
51 double mass;
52};
53
54void advance(int nbodies, struct planet * bodies, double dt)
55{
56 int i, j;
57
58 for (i = 0; i < nbodies; i++) {
59 struct planet * b = &(bodies[i]);
60 for (j = i + 1; j < nbodies; j++) {
61 struct planet * b2 = &(bodies[j]);
62 double dx = b->x - b2->x;
63 double dy = b->y - b2->y;
64 double dz = b->z - b2->z;
65 double distance = sqrt(dx * dx + dy * dy + dz * dz);
66 double mag = dt / (distance * distance * distance);
67 b->vx -= dx * b2->mass * mag;
68 b->vy -= dy * b2->mass * mag;
69 b->vz -= dz * b2->mass * mag;
70 b2->vx += dx * b->mass * mag;
71 b2->vy += dy * b->mass * mag;
72 b2->vz += dz * b->mass * mag;
73 }
74 }
75 for (i = 0; i < nbodies; i++) {
76 struct planet * b = &(bodies[i]);
77 b->x += dt * b->vx;
78 b->y += dt * b->vy;
79 b->z += dt * b->vz;
80 }
81}
82
83double energy(int nbodies, struct planet * bodies)
84{
85 double e;
86 int i, j;
87
88 e = 0.0;
89 for (i = 0; i < nbodies; i++) {
90 struct planet * b = &(bodies[i]);
91 e += 0.5 * b->mass * (b->vx * b->vx + b->vy * b->vy + b->vz * b->vz);
92 for (j = i + 1; j < nbodies; j++) {
93 struct planet * b2 = &(bodies[j]);
94 double dx = b->x - b2->x;
95 double dy = b->y - b2->y;
96 double dz = b->z - b2->z;
97 double distance = sqrt(dx * dx + dy * dy + dz * dz);
98 e -= (b->mass * b2->mass) / distance;
99 }
100 }
101 return e;
102}
103
104void offset_momentum(int nbodies, struct planet * bodies)
105{
106 double px = 0.0, py = 0.0, pz = 0.0;
107 int i;
108 for (i = 0; i < nbodies; i++) {
109 px += bodies[i].vx * bodies[i].mass;
110 py += bodies[i].vy * bodies[i].mass;
111 pz += bodies[i].vz * bodies[i].mass;
112 }
113 bodies[0].vx = - px / solar_mass;
114 bodies[0].vy = - py / solar_mass;
115 bodies[0].vz = - pz / solar_mass;
116}
117
118#define NBODIES 5
119struct planet bodies[NBODIES] = {
120 { /* sun */
121 0, 0, 0, 0, 0, 0, solar_mass
122 },
123 { /* jupiter */
124 4.84143144246472090e+00,
125 -1.16032004402742839e+00,
126 -1.03622044471123109e-01,
127 1.66007664274403694e-03 * days_per_year,
128 7.69901118419740425e-03 * days_per_year,
129 -6.90460016972063023e-05 * days_per_year,
130 9.54791938424326609e-04 * solar_mass
131 },
132 { /* saturn */
133 8.34336671824457987e+00,
134 4.12479856412430479e+00,
135 -4.03523417114321381e-01,
136 -2.76742510726862411e-03 * days_per_year,
137 4.99852801234917238e-03 * days_per_year,
138 2.30417297573763929e-05 * days_per_year,
139 2.85885980666130812e-04 * solar_mass
140 },
141 { /* uranus */
142 1.28943695621391310e+01,
143 -1.51111514016986312e+01,
144 -2.23307578892655734e-01,
145 2.96460137564761618e-03 * days_per_year,
146 2.37847173959480950e-03 * days_per_year,
147 -2.96589568540237556e-05 * days_per_year,
148 4.36624404335156298e-05 * solar_mass
149 },
150 { /* neptune */
151 1.53796971148509165e+01,
152 -2.59193146099879641e+01,
153 1.79258772950371181e-01,
154 2.68067772490389322e-03 * days_per_year,
155 1.62824170038242295e-03 * days_per_year,
156 -9.51592254519715870e-05 * days_per_year,
157 5.15138902046611451e-05 * solar_mass
158 }
159};
160
161int main(int argc, char ** argv)
162{
163 int n = atoi(argv[1]);
164 int i;
165
166 offset_momentum(NBODIES, bodies);
167 printf ("%.9f\n", energy(NBODIES, bodies));
168 for (i = 1; i <= n; i++)
169 advance(NBODIES, bodies, 0.01);
170 printf ("%.9f\n", energy(NBODIES, bodies));
171 return 0;
172}
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