source code
/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
contributed by Isaac Gouy
*/
import Glibc
struct Body {
var x, y, z, vx, vy, vz, mass : Double
mutating func advance(_ dt: Double) {
x += dt * vx
y += dt * vy
z += dt * vz
}
mutating func dec(_ vx: Double, _ vy: Double, _ vz: Double) {
self.vx -= vx
self.vy -= vy
self.vz -= vz
}
mutating func inc(_ vx: Double, _ vy: Double, _ vz: Double) {
self.vx += vx
self.vy += vy
self.vz += vz
}
}
let PI = 3.141592653589793
let SOLAR_MASS = 4 * PI * PI
let DAYS_PER_YEAR = 365.24
var bodies: [Body] = [
Body (
x: 0.0,
y: 0.0,
z: 0.0,
vx: 0.0,
vy: 0.0,
vz: 0.0,
mass: SOLAR_MASS
),
Body (
x: 4.84143144246472090e+00,
y: -1.16032004402742839e+00,
z: -1.03622044471123109e-01,
vx: 1.66007664274403694e-03 * DAYS_PER_YEAR,
vy: 7.69901118419740425e-03 * DAYS_PER_YEAR,
vz: -6.90460016972063023e-05 * DAYS_PER_YEAR,
mass: 9.54791938424326609e-04 * SOLAR_MASS
),
Body (
x: 8.34336671824457987e+00,
y: 4.12479856412430479e+00,
z: -4.03523417114321381e-01,
vx: -2.76742510726862411e-03 * DAYS_PER_YEAR,
vy: 4.99852801234917238e-03 * DAYS_PER_YEAR,
vz: 2.30417297573763929e-05 * DAYS_PER_YEAR,
mass: 2.85885980666130812e-04 * SOLAR_MASS
),
Body (
x: 1.28943695621391310e+01,
y: -1.51111514016986312e+01,
z: -2.23307578892655734e-01,
vx: 2.96460137564761618e-03 * DAYS_PER_YEAR,
vy: 2.37847173959480950e-03 * DAYS_PER_YEAR,
vz: -2.96589568540237556e-05 * DAYS_PER_YEAR,
mass: 4.36624404335156298e-05 * SOLAR_MASS
),
Body (
x: 1.53796971148509165e+01,
y: -2.59193146099879641e+01,
z: 1.79258772950371181e-01,
vx: 2.68067772490389322e-03 * DAYS_PER_YEAR,
vy: 1.62824170038242295e-03 * DAYS_PER_YEAR,
vz: -9.51592254519715870e-05 * DAYS_PER_YEAR,
mass: 5.15138902046611451e-05 * SOLAR_MASS
)
]
func offsetMomentum() {
var px = 0.0
var py = 0.0
var pz = 0.0
for body in bodies {
px += body.vx * body.mass
py += body.vy * body.mass
pz += body.vz * body.mass
}
bodies[0].inc(
-px / SOLAR_MASS,
-py / SOLAR_MASS,
-pz / SOLAR_MASS
)
}
func energy() -> Double {
var dx, dy, dz, distance: Double
var e = 0.0
for i in 0..<bodies.count {
e += 0.5 * bodies[i].mass *
( bodies[i].vx * bodies[i].vx
+ bodies[i].vy * bodies[i].vy
+ bodies[i].vz * bodies[i].vz )
for j in i+1..<bodies.count {
dx = bodies[i].x - bodies[j].x
dy = bodies[i].y - bodies[j].y
dz = bodies[i].z - bodies[j].z
distance = sqrt(dx*dx + dy*dy + dz*dz)
e -= (bodies[i].mass * bodies[j].mass) / distance
}
}
return e;
}
func advance(_ dt: Double) {
var dx, dy, dz, distance, mag: Double
for i in 0..<bodies.count {
for j in i+1..<bodies.count {
dx = bodies[i].x - bodies[j].x
dy = bodies[i].y - bodies[j].y
dz = bodies[i].z - bodies[j].z
distance = sqrt(dx*dx + dy*dy + dz*dz)
mag = dt / (distance * distance * distance)
bodies[i].dec(
dx * bodies[j].mass * mag,
dy * bodies[j].mass * mag,
dz * bodies[j].mass * mag
)
bodies[j].inc(
dx * bodies[i].mass * mag,
dy * bodies[i].mass * mag,
dz * bodies[i].mass * mag
)
}
}
for i in 0..<bodies.count {
bodies[i].advance(dt)
}
}
let n: Int = Int(CommandLine.arguments[1])!
offsetMomentum()
print( energy() )
for _ in 1...n {
advance(0.01)
}
print( energy() )