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Computer Language Benchmarks Game      [[ Play ]]

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 performance measurements

Each table row shows performance measurements for this Go program with a particular command-line input value N.

N	CPU secs	Elapsed secs	Memory KB	Code B	≈ CPU Load
500,000	0.36	0.37	260	1310	0% 3% 0% 100%
5,000,000	3.57	3.58	1,004	1310	1% 0% 0% 100%
50,000,000	35.70	35.71	1,004	1310	0% 1% 0% 100%

Read the ↓ make, command line, and program output logs to see how this program was run.

Read n-body benchmark to see what this program should do.

 notes

go version go1.1.1 linux/386

 n-body Go program source code

/* The Computer Language Benchmarks Game
 * http://benchmarksgame.alioth.debian.org/
 *
 * contributed by The Go Authors.
 * based on C program by Christoph Bauer
 * flag.Arg hack by Isaac Gouy
 */

package main

import (
   "flag"
   "fmt"
   "math"
   "strconv"
)

var n = 0

type Body struct {
   x, y, z, vx, vy, vz, mass float64
}

const (
   solarMass   = 4 * math.Pi * math.Pi
   daysPerYear = 365.24
)

func (b *Body) offsetMomentum(px, py, pz float64) {
   b.vx = -px / solarMass
   b.vy = -py / solarMass
   b.vz = -pz / solarMass
}

type System []*Body

func NewSystem(body []Body) System {
   n := make(System, len(body))
   for i := 0; i < len(body); i++ {
      n[i] = new(Body) // copy to avoid overwriting the inputs
      *n[i] = body[i]
   }
   var px, py, pz float64
   for _, body := range n {
      px += body.vx * body.mass
      py += body.vy * body.mass
      pz += body.vz * body.mass
   }
   n[0].offsetMomentum(px, py, pz)
   return n
}

func (sys System) energy() float64 {
   var e float64
   for i, body := range sys {
      e += 0.5 * body.mass *
         (body.vx*body.vx + body.vy*body.vy + body.vz*body.vz)
      for j := i + 1; j < len(sys); j++ {
         body2 := sys[j]
         dx := body.x - body2.x
         dy := body.y - body2.y
         dz := body.z - body2.z
         distance := math.Sqrt(dx*dx + dy*dy + dz*dz)
         e -= (body.mass * body2.mass) / distance
      }
   }
   return e
}

func (sys System) advance(dt float64) {
   for i, body := range sys {
      for j := i + 1; j < len(sys); j++ {
         body2 := sys[j]
         dx := body.x - body2.x
         dy := body.y - body2.y
         dz := body.z - body2.z

         dSquared := dx*dx + dy*dy + dz*dz
         distance := math.Sqrt(dSquared)
         mag := dt / (dSquared * distance)

         body.vx -= dx * body2.mass * mag
         body.vy -= dy * body2.mass * mag
         body.vz -= dz * body2.mass * mag

         body2.vx += dx * body.mass * mag
         body2.vy += dy * body.mass * mag
         body2.vz += dz * body.mass * mag
      }
   }

   for _, body := range sys {
      body.x += dt * body.vx
      body.y += dt * body.vy
      body.z += dt * body.vz
   }
}

var (
   jupiter = Body{
      x: 4.84143144246472090e+00,
      y: -1.16032004402742839e+00,
      z: -1.03622044471123109e-01,
      vx: 1.66007664274403694e-03 * daysPerYear,
      vy: 7.69901118419740425e-03 * daysPerYear,
      vz: -6.90460016972063023e-05 * daysPerYear,
      mass: 9.54791938424326609e-04 * solarMass,
   }
   saturn = Body{
      x: 8.34336671824457987e+00,
      y: 4.12479856412430479e+00,
      z: -4.03523417114321381e-01,
      vx: -2.76742510726862411e-03 * daysPerYear,
      vy: 4.99852801234917238e-03 * daysPerYear,
      vz: 2.30417297573763929e-05 * daysPerYear,
      mass: 2.85885980666130812e-04 * solarMass,
   }
   uranus = Body{
      x: 1.28943695621391310e+01,
      y: -1.51111514016986312e+01,
      z: -2.23307578892655734e-01,
      vx: 2.96460137564761618e-03 * daysPerYear,
      vy: 2.37847173959480950e-03 * daysPerYear,
      vz: -2.96589568540237556e-05 * daysPerYear,
      mass: 4.36624404335156298e-05 * solarMass,
   }
   neptune = Body{
      x: 1.53796971148509165e+01,
      y: -2.59193146099879641e+01,
      z: 1.79258772950371181e-01,
      vx: 2.68067772490389322e-03 * daysPerYear,
      vy: 1.62824170038242295e-03 * daysPerYear,
      vz: -9.51592254519715870e-05 * daysPerYear,
      mass: 5.15138902046611451e-05 * solarMass,
   }
   sun = Body{
      mass: solarMass,
   }
)

func main() {
   flag.Parse()
   if flag.NArg() > 0 { n,_ = strconv.Atoi( flag.Arg(0) ) }

   system := NewSystem([]Body{sun, jupiter, saturn, uranus, neptune})
   fmt.Printf("%.9f\n", system.energy())
   for i := 0; i < n; i++ {
      system.advance(0.01)
   }
   fmt.Printf("%.9f\n", system.energy())
}

 make, command-line, and program output logs

Thu, 13 Jun 2013 20:52:31 GMT

MAKE:
/usr/local/src/go/bin/go build -o nbody.go_run
0.30s to complete and log all make actions

COMMAND LINE:
./nbody.go_run 50000000

PROGRAM OUTPUT:
-0.169075164
-0.169059907

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