/
1.kt
191 lines (161 loc) · 5.44 KB
/
1.kt
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/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
Based on Java n-body by Mark C. Lewis, Chad Whipkey
Feldbinder, and Tagir Valeev
Contributed by Hank Grabowski
*/
import kotlin.math.*
fun main(args: Array<String>) {
val n = if (args.size > 0) args[0].toInt() else 1000
val bodies = NBodySystem()
println("%.9f".format(bodies.energy()))
for (i in 0..n - 1) bodies.advance(0.01)
println("%.9f".format(bodies.energy()))
}
internal class NBodySystem {
private val bodies: Array<Body>
init {
bodies = arrayOf(Body.sun(), Body.jupiter(), Body.saturn(), Body.uranus(), Body.neptune())
var px = 0.0
var py = 0.0
var pz = 0.0
for (i in 0..LENGTH - 1) {
px += bodies[i].vx * bodies[i].mass
py += bodies[i].vy * bodies[i].mass
pz += bodies[i].vz * bodies[i].mass
}
bodies[0].offsetMomentum(px, py, pz)
}
fun advance(dt: Double) {
val b = bodies
for (i in 0..LENGTH - 1) {
val iBody = b[i]
val iMass = iBody.mass
val ix = iBody.x
val iy = iBody.y
val iz = iBody.z
var vx = iBody.vx
var vy = iBody.vy
var vz = iBody.vz
for (j in i + 1..LENGTH - 1) {
val jBody = b[j]
val dx = ix - jBody.x
val dy = iy - jBody.y
val dz = iz - jBody.z
val dSquared = dx * dx + dy * dy + dz * dz
val distance = kotlin.math.sqrt(dSquared)
val mag = dt / (dSquared * distance)
val jMass = jBody.mass
val mjMag = jMass * mag
vx -= dx * mjMag
vy -= dy * mjMag
vz -= dz * mjMag
val miMag = iMass * mag
jBody.vx += dx * miMag
jBody.vy += dy * miMag
jBody.vz += dz * miMag
}
iBody.vx = vx
iBody.vy = vy
iBody.vz = vz
iBody.x += dt * vx
iBody.y += dt * vy
iBody.z += dt * vz
}
}
fun energy(): Double {
var dx: Double
var dy: Double
var dz: Double
var distance: Double
var e = 0.0
for (i in bodies.indices) {
val iBody = bodies[i]
e +=
0.5 *
iBody.mass *
(iBody.vx * iBody.vx + iBody.vy * iBody.vy + iBody.vz * iBody.vz)
for (j in i + 1..bodies.size - 1) {
val jBody = bodies[j]
dx = iBody.x - jBody.x
dy = iBody.y - jBody.y
dz = iBody.z - jBody.z
distance = kotlin.math.sqrt(dx * dx + dy * dy + dz * dz)
e -= iBody.mass * jBody.mass / distance
}
}
return e
}
companion object {
private val LENGTH = 5
}
}
internal class Body {
var x: Double = 0.toDouble()
var y: Double = 0.toDouble()
var z: Double = 0.toDouble()
var vx: Double = 0.toDouble()
var vy: Double = 0.toDouble()
var vz: Double = 0.toDouble()
var mass: Double = 0.toDouble()
fun offsetMomentum(px: Double, py: Double, pz: Double): Body {
vx = -px / SOLAR_MASS
vy = -py / SOLAR_MASS
vz = -pz / SOLAR_MASS
return this
}
companion object {
val PI = 3.141592653589793
val SOLAR_MASS = 4.0 * PI * PI
val DAYS_PER_YEAR = 365.24
fun jupiter(): Body {
val p = Body()
p.x = 4.84143144246472090e+00
p.y = -1.16032004402742839e+00
p.z = -1.03622044471123109e-01
p.vx = 1.66007664274403694e-03 * DAYS_PER_YEAR
p.vy = 7.69901118419740425e-03 * DAYS_PER_YEAR
p.vz = -6.90460016972063023e-05 * DAYS_PER_YEAR
p.mass = 9.54791938424326609e-04 * SOLAR_MASS
return p
}
fun saturn(): Body {
val p = Body()
p.x = 8.34336671824457987e+00
p.y = 4.12479856412430479e+00
p.z = -4.03523417114321381e-01
p.vx = -2.76742510726862411e-03 * DAYS_PER_YEAR
p.vy = 4.99852801234917238e-03 * DAYS_PER_YEAR
p.vz = 2.30417297573763929e-05 * DAYS_PER_YEAR
p.mass = 2.85885980666130812e-04 * SOLAR_MASS
return p
}
fun uranus(): Body {
val p = Body()
p.x = 1.28943695621391310e+01
p.y = -1.51111514016986312e+01
p.z = -2.23307578892655734e-01
p.vx = 2.96460137564761618e-03 * DAYS_PER_YEAR
p.vy = 2.37847173959480950e-03 * DAYS_PER_YEAR
p.vz = -2.96589568540237556e-05 * DAYS_PER_YEAR
p.mass = 4.36624404335156298e-05 * SOLAR_MASS
return p
}
fun neptune(): Body {
val p = Body()
p.x = 1.53796971148509165e+01
p.y = -2.59193146099879641e+01
p.z = 1.79258772950371181e-01
p.vx = 2.68067772490389322e-03 * DAYS_PER_YEAR
p.vy = 1.62824170038242295e-03 * DAYS_PER_YEAR
p.vz = -9.51592254519715870e-05 * DAYS_PER_YEAR
p.mass = 5.15138902046611451e-05 * SOLAR_MASS
return p
}
fun sun(): Body {
val p = Body()
p.mass = SOLAR_MASS
return p
}
}
}