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accelerated SIMD n-body (https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/nbody-swift-7.html)
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| /* The Computer Language Benchmarks Game | |
| https://salsa.debian.org/benchmarksgame-team/benchmarksgame/ | |
| contributed by Ralph Ganszky | |
| Added dummy element to tuple (because I read an article that this helps | |
| to block less writing back to memory) and store data in | |
| UnsafedMutablePointer to reduce overhead of array access. | |
| modified by Patrick Sy | |
| modified by Jens Kaiser | |
| */ | |
| import Foundation | |
| import simd | |
| typealias Body = ( | |
| r: simd_double3, | |
| v: simd_double3, | |
| m: simd_double1, | |
| d: simd_double1 | |
| ) | |
| let nPlanets: Int = 5 | |
| let solarMass: Double = 4 * Double.pi * Double.pi | |
| let daysPerYear: Double = 365.24 | |
| let sun: Body = ( | |
| r: simd_double3(x: 0.0, y: 0.0, z: 0.0), | |
| v: simd_double3(x: 0.0, y: 0.0, z: 0.0), | |
| m: solarMass, d: 0.0 | |
| ) | |
| let jupiter: Body = ( | |
| r: simd_double3(x: 4.8414314424647209, | |
| y: -1.16032004402742839, | |
| z: -0.103622044471123109), | |
| v: simd_double3(x: 1.66007664274403694e-03 * daysPerYear, | |
| y: 7.69901118419740425e-03 * daysPerYear, | |
| z: -6.90460016972063023e-05 * daysPerYear), | |
| m: 9.54791938424326609e-04 * solarMass, d: 0.0 | |
| ) | |
| let saturn: Body = ( | |
| r: simd_double3(x: 8.34336671824457987, | |
| y: 4.12479856412430479, | |
| z: -4.03523417114321381e-01), | |
| v: simd_double3(x: -2.76742510726862411e-03 * daysPerYear, | |
| y: 4.99852801234917238e-03 * daysPerYear, | |
| z: 2.30417297573763929e-05 * daysPerYear), | |
| m: 2.85885980666130812e-04 * solarMass, d: 0.0 | |
| ) | |
| let uranus: Body = ( | |
| r: simd_double3(x: 1.28943695621391310e+01, | |
| y: -1.51111514016986312e+01, | |
| z: -2.23307578892655734e-01), | |
| v: simd_double3(x: 2.96460137564761618e-03 * daysPerYear, | |
| y: 2.37847173959480950e-03 * daysPerYear, | |
| z: -2.96589568540237556e-05 * daysPerYear), | |
| m: 4.36624404335156298e-05 * solarMass, d: 0.0 | |
| ) | |
| let neptune: Body = ( | |
| r: simd_double3(x: 1.53796971148509165e+01, | |
| y: -2.59193146099879641e+01, | |
| z: 1.79258772950371181e-01), | |
| v: simd_double3(x: 2.68067772490389322e-03 * daysPerYear, | |
| y: 1.62824170038242295e-03 * daysPerYear, | |
| z: -9.51592254519715870e-05 * daysPerYear), | |
| m: 5.15138902046611451e-05 * solarMass, d: 0.0 | |
| ) | |
| let bodies: UnsafeMutablePointer<Body> = UnsafeMutablePointer<Body>.allocate(capacity: nPlanets) | |
| defer { | |
| bodies.deallocate() | |
| } | |
| bodies[0] = sun | |
| bodies[1] = jupiter | |
| bodies[2] = saturn | |
| bodies[3] = uranus | |
| bodies[4] = neptune | |
| func advance(dt: simd_double1) { | |
| for i in 0..<nPlanets { | |
| let iBody: Body = bodies[i] | |
| for j in i+1..<nPlanets { | |
| let jBody: Body = bodies[j] | |
| let d: simd_double3 = iBody.r - jBody.r | |
| let dSquared: simd_double1 = simd_length_squared(d) | |
| let mag: simd_double1 = dt / (dSquared * dSquared.squareRoot()) | |
| // dSquared.squareRoot() == distance | |
| bodies[i].v -= d * (jBody.m * mag) | |
| bodies[j].v += d * (iBody.m * mag) | |
| } | |
| } | |
| for i in 0..<nPlanets { | |
| bodies[i].r = bodies[i].r + bodies[i].v * dt | |
| } | |
| } | |
| func energy() -> simd_double1 { | |
| var energy: simd_double1 = 0.0 | |
| for i in 0..<nPlanets { | |
| let iBody: Body = bodies[i] | |
| energy += 0.5 * iBody.m * simd_length_squared(iBody.v) | |
| for j in i+1..<nPlanets { | |
| let jBody: Body = bodies[j] | |
| let d: simd_double3 = iBody.r - jBody.r | |
| let distance: simd_double1 = simd_length(d) | |
| energy -= (iBody.m * jBody.m) / distance | |
| } | |
| } | |
| return energy | |
| } | |
| var n: Int = 1000 | |
| if CommandLine.argc > 1 { | |
| if let m: Int = Int(CommandLine.arguments[1]) { | |
| n = m | |
| } | |
| } | |
| // Adjust momentum of the sun | |
| var p: simd_double3 = simd_double3(x: 0.0, y: 0.0, z: 0.0) | |
| for i in 0..<nPlanets { | |
| p += bodies[i].v * bodies[i].m | |
| } | |
| bodies[0].v = -p / solarMass | |
| print(String(format: "%.9f", energy())) | |
| for _ in 0..<n { | |
| advance(dt: 0.01) | |
| } | |
| print(String(format: "%.9f", energy())) |
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