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![Rob Pike](/assets/img/avatar_default.png)
timing.sh improvements R=rsc DELTA=334 (319 added, 0 deleted, 15 changed) OCL=32734 CL=32736
178 lines
4.9 KiB
Go
178 lines
4.9 KiB
Go
/*
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of "The Computer Language Benchmarks Game" nor the
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name of "The Computer Language Shootout Benchmarks" nor the names of
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its contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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/* The Computer Language Benchmarks Game
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* http://shootout.alioth.debian.org/
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*
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* contributed by The Go Authors.
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* based on C program by Christoph Bauer
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*/
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package main
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import (
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"flag";
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"fmt";
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"math";
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)
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var n = flag.Int("n", 1000, "number of iterations")
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type Body struct {
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x, y, z, vx, vy, vz, mass float64
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}
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const (
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solarMass = 4 * math.Pi * math.Pi;
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daysPerYear = 365.24;
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)
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func (b *Body) offsetMomentum(px, py, pz float64){
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b.vx = -px / solarMass;
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b.vy = -py / solarMass;
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b.vz = -pz / solarMass;
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}
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type System []*Body
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func NewSystem(body []Body) System {
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n := make(System, len(body));
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for i := 0; i < len(body); i++ {
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n[i] = new(Body); // copy to avoid overwriting the inputs
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*n[i] = body[i];
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}
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var px, py, pz float64;
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for _, body := range n {
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px += body.vx * body.mass;
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py += body.vy * body.mass;
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pz += body.vz * body.mass;
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}
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n[0].offsetMomentum(px, py, pz);
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return n;
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}
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func (sys System) energy() float64 {
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var e float64;
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for i, body := range sys {
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e += 0.5 * body.mass *
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(body.vx*body.vx + body.vy*body.vy + body.vz*body.vz);
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for j := i+1; j < len(sys); j++ {
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body2 := sys[j];
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dx := body.x - body2.x;
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dy := body.y - body2.y;
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dz := body.z - body2.z;
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distance := math.Sqrt(dx*dx + dy*dy + dz*dz);
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e -= (body.mass * body2.mass) / distance;
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}
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}
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return e;
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}
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func (sys System) advance(dt float64) {
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for i, body := range sys {
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for j := i+1; j < len(sys); j++ {
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body2 := sys[j];
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dx := body.x - body2.x;
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dy := body.y - body2.y;
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dz := body.z - body2.z;
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dSquared := dx*dx + dy*dy + dz*dz;
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distance := math.Sqrt(dSquared);
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mag := dt / (dSquared * distance);
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body.vx -= dx * body2.mass * mag;
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body.vy -= dy * body2.mass * mag;
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body.vz -= dz * body2.mass * mag;
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body2.vx += dx * body.mass * mag;
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body2.vy += dy * body.mass * mag;
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body2.vz += dz * body.mass * mag;
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}
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}
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for _, body := range sys {
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body.x += dt * body.vx;
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body.y += dt * body.vy;
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body.z += dt * body.vz;
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}
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}
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var (
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jupiter = Body {
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x: 4.84143144246472090e+00,
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y: -1.16032004402742839e+00,
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z: -1.03622044471123109e-01,
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vx: 1.66007664274403694e-03 * daysPerYear,
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vy: 7.69901118419740425e-03 * daysPerYear,
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vz: -6.90460016972063023e-05 * daysPerYear,
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mass: 9.54791938424326609e-04 * solarMass,
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};
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saturn = Body {
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x: 8.34336671824457987e+00,
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y: 4.12479856412430479e+00,
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z: -4.03523417114321381e-01,
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vx: -2.76742510726862411e-03 * daysPerYear,
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vy: 4.99852801234917238e-03 * daysPerYear,
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vz: 2.30417297573763929e-05 * daysPerYear,
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mass: 2.85885980666130812e-04 * solarMass,
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};
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uranus = Body {
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x: 1.28943695621391310e+01,
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y: -1.51111514016986312e+01,
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z: -2.23307578892655734e-01,
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vx: 2.96460137564761618e-03 * daysPerYear,
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vy: 2.37847173959480950e-03 * daysPerYear,
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vz: -2.96589568540237556e-05 * daysPerYear,
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mass: 4.36624404335156298e-05 * solarMass,
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};
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neptune = Body {
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x: 1.53796971148509165e+01,
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y: -2.59193146099879641e+01,
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z: 1.79258772950371181e-01,
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vx: 2.68067772490389322e-03 * daysPerYear,
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vy: 1.62824170038242295e-03 * daysPerYear,
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vz: -9.51592254519715870e-05 * daysPerYear,
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mass: 5.15138902046611451e-05 * solarMass,
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};
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sun = Body {
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mass: solarMass
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}
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)
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func main() {
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flag.Parse();
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system := NewSystem([]Body{sun, jupiter, saturn, uranus, neptune});
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fmt.Printf("%.9f\n", system.energy());
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for i := 0; i < *n; i++ {
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system.advance(0.01)
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}
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fmt.Printf("%.9f\n", system.energy());
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}
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