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
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
|
// based on:
// http://shootout.alioth.debian.org/u32/benchmark.php?test=nbody&lang=java
fn main() {
let vec[int] inputs = vec(
50000
//these segfault :(
//500000,
//5000000,
//50000000
);
let vec[Body.props] bodies = NBodySystem.MakeNBodySystem();
for (int n in inputs) {
// TODO: make #fmt handle floats?
log NBodySystem.energy(bodies);
let int i = 0;
while (i < n) {
bodies = NBodySystem.advance(bodies, 0.01);
i = i+1;
}
log NBodySystem.energy(bodies);
}
}
// making a native call to sqrt
native "rust" mod rustrt {
fn squareroot(&float input, &mutable float output);
}
// Body.props is a record of floats, so
// vec[Body.props] is a vector of records of floats
mod NBodySystem {
fn MakeNBodySystem() -> vec[Body.props] {
// can't iterate over a record? how about a vector, then?
let vec[Body.props] bodies = vec(
// these each return a Body.props
Body.sun(),
Body.jupiter(),
Body.saturn(),
Body.uranus(),
Body.neptune());
let float px = 0.0;
let float py = 0.0;
let float pz = 0.0;
for (Body.props body in bodies) {
px += body.vx * body.mass;
py += body.vy * body.mass;
pz += body.vz * body.mass;
}
bodies.(0) = Body.offsetMomentum(bodies.(0), px, py, pz);
ret bodies;
}
fn advance(vec[Body.props] bodies, float dt) -> vec[Body.props] {
for (Body.props ibody in bodies) {
let Body.props iBody = ibody;
for (Body.props jbody in bodies) {
let float dx = iBody.x - jbody.x;
let float dy = iBody.y - jbody.y;
let float dz = iBody.z - jbody.z;
let float dSquared = dx * dx + dy * dy + dz * dz;
let float distance;
rustrt.squareroot(dSquared, distance);
let float mag = dt / (dSquared * distance);
}
}
for (Body.props body in bodies) {
body.x += dt * body.vx;
body.y += dt * body.vy;
body.z += dt * body.vz;
}
ret bodies;
}
fn energy(vec[Body.props] bodies) -> float {
let float dx;
let float dy;
let float dz;
let float distance;
let float e = 0.0;
for (Body.props ibody in bodies) {
// do we need this?
let Body.props iBody = ibody;
e += 0.5 * iBody.mass *
( iBody.vx * iBody.vx
+ iBody.vy * iBody.vy
+ iBody.vz * iBody.vz );
for (Body.props jbody in bodies) {
// do we need this?
let Body.props jBody = jbody;
dx = iBody.x - jBody.x;
dy = iBody.y - jBody.y;
dz = iBody.z - jBody.z;
rustrt.squareroot(dx*dx + dy*dy + dz*dz, distance);
e -= (iBody.mass * jBody.mass) / distance;
}
}
ret e;
}
}
mod Body {
const float PI = 3.141592;
const float SOLAR_MASS = 39.478417; // was 4 * PI * PI originally
const float DAYS_PER_YEAR = 365.24;
type props = rec(float x,
float y,
float z,
float vx,
float vy,
float vz,
float mass);
fn jupiter() -> Body.props {
// current limitation of the float lexer: decimal part has to
// fit into a 32-bit int.
let Body.props p;
p.x = 4.841431e+00;
p.y = -1.160320e+00;
p.z = -1.036220e-01;
p.vx = 1.660076e-03 * DAYS_PER_YEAR;
p.vy = 7.699011e-03 * DAYS_PER_YEAR;
p.vz = -6.904600e-05 * DAYS_PER_YEAR;
p.mass = 9.547919e-04 * SOLAR_MASS;
ret p;
}
fn saturn() -> Body.props {
let Body.props p;
p.x = 8.343366e+00;
p.y = 4.124798e+00;
p.z = -4.035234e-01;
p.vx = -2.767425e-03 * DAYS_PER_YEAR;
p.vy = 4.998528e-03 * DAYS_PER_YEAR;
p.vz = 2.304172e-05 * DAYS_PER_YEAR;
p.mass = 2.858859e-04 * SOLAR_MASS;
ret p;
}
fn uranus() -> Body.props {
let Body.props p;
p.x = 1.289436e+01;
p.y = -1.511115e+01;
p.z = -2.233075e-01;
p.vx = 2.964601e-03 * DAYS_PER_YEAR;
p.vy = 2.378471e-03 * DAYS_PER_YEAR;
p.vz = -2.965895e-05 * DAYS_PER_YEAR;
p.mass = 4.366244e-05 * SOLAR_MASS;
ret p;
}
fn neptune() -> Body.props {
let Body.props p;
p.x = 1.537969e+01;
p.y = -2.591931e+01;
p.z = 1.792587e-01;
p.vx = 2.680677e-03 * DAYS_PER_YEAR;
p.vy = 1.628241e-03 * DAYS_PER_YEAR;
p.vz = -9.515922e-05 * DAYS_PER_YEAR;
p.mass = 5.151389e-05 * SOLAR_MASS;
ret p;
}
fn sun() -> Body.props {
let Body.props p;
p.mass = SOLAR_MASS;
ret p;
}
fn offsetMomentum(Body.props props,
float px,
float py,
float pz) -> Body.props {
// TODO: should we create a new one or mutate the original?
let Body.props p = props;
p.vx = -px / SOLAR_MASS;
p.vy = -py / SOLAR_MASS;
p.vz = -pz / SOLAR_MASS;
ret p;
}
}
|