source code
/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
contributed by Ralph Ganszky
*/
import Glibc
let SOLAR_MASS = 4 * M_PI * M_PI
let DAYS_PER_YEAR = 365.24
var sun = ( (0.0, 0.0, 0.0), (0.0, 0.0, 0.0), SOLAR_MASS )
var jupiter = ( (4.8414314424647209,
-1.16032004402742839,
-0.103622044471123109),
(1.66007664274403694e-03 * DAYS_PER_YEAR,
7.69901118419740425e-03 * DAYS_PER_YEAR,
-6.90460016972063023e-05 * DAYS_PER_YEAR),
9.54791938424326609e-04 * SOLAR_MASS )
var saturn = ( (8.34336671824457987,
4.12479856412430479,
-4.03523417114321381e-01),
(-2.76742510726862411e-03 * DAYS_PER_YEAR,
4.99852801234917238e-03 * DAYS_PER_YEAR,
2.30417297573763929e-05 * DAYS_PER_YEAR),
2.85885980666130812e-04 * SOLAR_MASS )
var uranus = ( (1.28943695621391310e+01,
-1.51111514016986312e+01,
-2.23307578892655734e-01),
(2.96460137564761618e-03 * DAYS_PER_YEAR,
2.37847173959480950e-03 * DAYS_PER_YEAR,
-2.96589568540237556e-05 * DAYS_PER_YEAR),
4.36624404335156298e-05 * SOLAR_MASS)
var neptune = ( (1.53796971148509165e+01,
-2.59193146099879641e+01,
1.79258772950371181e-01),
(2.68067772490389322e-03 * DAYS_PER_YEAR,
1.62824170038242295e-03 * DAYS_PER_YEAR,
-9.51592254519715870e-05 * DAYS_PER_YEAR),
5.15138902046611451e-05 * SOLAR_MASS)
var bodies = [sun, jupiter, saturn, uranus, neptune]
func advance(_ bodies: inout [((Double,Double,Double),
(Double,Double,Double),
Double)], dt: Double) {
for i in 0..<bodies.count {
for j in i+1..<bodies.count {
let (dx, dy, dz) = (bodies[i].0.0 - bodies[j].0.0,
bodies[i].0.1 - bodies[j].0.1,
bodies[i].0.2 - bodies[j].0.2)
let dSquared = dx*dx + dy*dy + dz*dz
let distance = sqrt(dSquared)
let mag = dt / (dSquared * distance)
bodies[i].1 = (bodies[i].1.0 - dx * bodies[j].2 * mag,
bodies[i].1.1 - dy * bodies[j].2 * mag,
bodies[i].1.2 - dz * bodies[j].2 * mag)
bodies[j].1 = (bodies[j].1.0 + dx * bodies[i].2 * mag,
bodies[j].1.1 + dy * bodies[i].2 * mag,
bodies[j].1.2 + dz * bodies[i].2 * mag)
}
}
for i in 0..<bodies.count {
bodies[i].0 = (bodies[i].0.0 + dt * bodies[i].1.0,
bodies[i].0.1 + dt * bodies[i].1.1,
bodies[i].0.2 + dt * bodies[i].1.2)
}
}
func energy(_ bodies: [((Double,Double,Double),
(Double,Double,Double),
Double)]) -> Double {
var energy = 0.0
for (i, body) in bodies.enumerated() {
energy += 0.5 * body.2 * ( body.1.0*body.1.0
+ body.1.1*body.1.1
+ body.1.2*body.1.2)
for jbody in bodies[i+1..<bodies.count] {
let dx = body.0.0 - jbody.0.0
let dy = body.0.1 - jbody.0.1
let dz = body.0.2 - jbody.0.2
let distance = sqrt(dx*dx + dy*dy + dz*dz)
energy -= (body.2 * jbody.2) / distance
}
}
return energy
}
let n: Int
if CommandLine.argc > 1 {
n = Int(CommandLine.arguments[1]) ?? 1000
} else {
n = 1000
}
// Adjust momentum of the sun
var p = (0.0, 0.0, 0.0)
for body in bodies {
p.0 += body.1.0 * body.2
p.1 += body.1.1 * body.2
p.2 += body.1.2 * body.2
}
bodies[0].1 = (-p.0 / SOLAR_MASS, -p.1 / SOLAR_MASS, -p.2 / SOLAR_MASS)
print("\(energy(bodies))")
for i in 0..<n {
advance(&bodies, dt: 0.01)
}
print("\(energy(bodies))")