diff options
Diffstat (limited to 'test/bench/nbody.go')
| -rw-r--r-- | test/bench/nbody.go | 120 |
1 files changed, 60 insertions, 60 deletions
diff --git a/test/bench/nbody.go b/test/bench/nbody.go index 05831bba2..e9f4517e8 100644 --- a/test/bench/nbody.go +++ b/test/bench/nbody.go @@ -37,94 +37,94 @@ POSSIBILITY OF SUCH DAMAGE. package main import ( - "flag"; - "fmt"; - "math"; + "flag" + "fmt" + "math" ) var n = flag.Int("n", 1000, "number of iterations") type Body struct { - x, y, z, vx, vy, vz, mass float64; + x, y, z, vx, vy, vz, mass float64 } const ( - solarMass = 4 * math.Pi * math.Pi; - daysPerYear = 365.24; + 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; + 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)); + 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]; + n[i] = new(Body) // copy to avoid overwriting the inputs + *n[i] = body[i] } - var px, py, pz float64; + var px, py, pz float64 for _, body := range n { - px += body.vx * body.mass; - py += body.vy * body.mass; - pz += body.vz * body.mass; + px += body.vx * body.mass + py += body.vy * body.mass + pz += body.vz * body.mass } - n[0].offsetMomentum(px, py, pz); - return n; + n[0].offsetMomentum(px, py, pz) + return n } func (sys System) energy() float64 { - var e 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); + (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; + 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; + 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; + 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; + body.x += dt * body.vx + body.y += dt * body.vy + body.z += dt * body.vz } } var ( - jupiter = Body{ + jupiter = Body{ x: 4.84143144246472090e+00, y: -1.16032004402742839e+00, z: -1.03622044471123109e-01, @@ -132,8 +132,8 @@ var ( vy: 7.69901118419740425e-03 * daysPerYear, vz: -6.90460016972063023e-05 * daysPerYear, mass: 9.54791938424326609e-04 * solarMass, - }; - saturn = Body{ + } + saturn = Body{ x: 8.34336671824457987e+00, y: 4.12479856412430479e+00, z: -4.03523417114321381e-01, @@ -141,8 +141,8 @@ var ( vy: 4.99852801234917238e-03 * daysPerYear, vz: 2.30417297573763929e-05 * daysPerYear, mass: 2.85885980666130812e-04 * solarMass, - }; - uranus = Body{ + } + uranus = Body{ x: 1.28943695621391310e+01, y: -1.51111514016986312e+01, z: -2.23307578892655734e-01, @@ -150,8 +150,8 @@ var ( vy: 2.37847173959480950e-03 * daysPerYear, vz: -2.96589568540237556e-05 * daysPerYear, mass: 4.36624404335156298e-05 * solarMass, - }; - neptune = Body{ + } + neptune = Body{ x: 1.53796971148509165e+01, y: -2.59193146099879641e+01, z: 1.79258772950371181e-01, @@ -159,19 +159,19 @@ var ( vy: 1.62824170038242295e-03 * daysPerYear, vz: -9.51592254519715870e-05 * daysPerYear, mass: 5.15138902046611451e-05 * solarMass, - }; - sun = Body{ + } + sun = Body{ mass: solarMass, - }; + } ) func main() { - flag.Parse(); + flag.Parse() - system := NewSystem([]Body{sun, jupiter, saturn, uranus, neptune}); - fmt.Printf("%.9f\n", system.energy()); + 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()); + fmt.Printf("%.9f\n", system.energy()) } |