* renamed nbody to n_body

git-svn-id: trunk@9677 -

.gitattributes

@@ -5974,6 +5974,7 @@ tests/bench/shootout/src/knucleotide.pp svneol=native#text/plain
 tests/bench/shootout/src/mandelbrot.pp svneol=native#text/plain
 tests/bench/shootout/src/message.pp svneol=native#text/plain
 tests/bench/shootout/src/meteorshower.pp svneol=native#text/x-pascal
+tests/bench/shootout/src/n_body.pp svneol=native#text/plain
 tests/bench/shootout/src/nbody.pp svneol=native#text/plain
 tests/bench/shootout/src/nsieve.pp svneol=native#text/plain
 tests/bench/shootout/src/partialsums.pp svneol=native#text/plain

tests/bench/shootout/src/n_body.pp

@@ -0,0 +1,149 @@
+{ The Computer Language Shootout
+  http://shootout.alioth.debian.org
+
+  contributed by Ian Osgood,
+  modified by Florian Klaempfl
+  modified by Ales Katona
+  modified by Vincent Snijders
+}
+{$mode objfpc}
+
+program n_body;
+
+uses Math;
+
+type
+  Body = record
+    x, y, z,
+    vx, vy, vz,
+    mass : double;
+  end;
+  PBody = ^Body;
+
+const pi = 3.141592653589793;
+      solarMass = 4 * sqr(pi);
+      daysPerYear = 365.24;
+
+type
+  tbody = array[1..5] of Body;
+
+const b : tbody = (
+  { Sun }
+  ( x:0; y:0; z:0;  vx:0; vy:0; vz:0;  mass: solarMass ),
+  { Jupiter }
+  ( 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 }
+  ( 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 }
+  ( 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 }
+  ( 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 )
+);
+
+procedure offsetMomentum;
+var px,py,pz : double;
+    i : integer;
+begin
+  px:=0.0; py:=0.0; pz:=0.0;
+  for i := low(b)+1 to high(b) do
+    with b[i] do
+    begin
+      px := px - vx * mass;
+      py := py - vy * mass;
+      pz := pz - vz * mass;
+    end;
+  b[low(b)].vx := px / solarMass;
+  b[low(b)].vy := py / solarMass;
+  b[low(b)].vz := pz / solarMass;
+end;
+
+function distance(i,j : integer) : double;
+begin
+  distance := sqrt(sqr(b[i].x-b[j].x) + sqr(b[i].y-b[j].y) +
+sqr(b[i].z-b[j].z));
+end;
+
+function energy : double;
+var
+  i,j : integer;
+begin
+  result := 0.0;
+  for i := low(b) to high(b) do
+    with b[i] do
+    begin
+      result := result + mass * (sqr(vx) + sqr(vy) + sqr(vz)) / 2;
+      for j := i+1 to high(b) do
+        result := result - mass * b[j].mass / distance(i,j);
+    end;
+end;
+
+procedure advance(dt : double);
+var i,j : integer;
+    dx,dy,dz,mag : double;
+    bi,bj : PBody;
+begin
+  bi:=@b[low(b)];
+  for i := low(b) to high(b)-1 do begin
+    bj := bi;
+    for j := i+1 to high(b) do
+    begin
+      inc(bj);
+      dx := bi^.x - bj^.x;
+      dy := bi^.y - bj^.y;
+      dz := bi^.z - bj^.z;
+      mag := dt / (sqrt(sqr(dx)+sqr(dy)+sqr(dz))*(sqr(dx)+sqr(dy)+sqr(dz)));
+      bi^.vx := bi^.vx - dx * bj^.mass * mag;
+      bi^.vy := bi^.vy - dy * bj^.mass * mag;
+      bi^.vz := bi^.vz - dz * bj^.mass * mag;
+      bj^.vx := bj^.vx + dx * bi^.mass * mag;
+      bj^.vy := bj^.vy + dy * bi^.mass * mag;
+      bj^.vz := bj^.vz + dz * bi^.mass * mag;
+    end;
+    inc(bi);
+  end;
+  bi:=@b[low(b)];
+  for i := low(b) to high(b) do begin
+    with bi^ do
+    begin
+      x := x + dt * vx;
+      y := y + dt * vy;
+      z := z + dt * vz;
+    end;
+    inc(bi);
+  end;
+end;
+
+var i : integer;
+    n : Integer;
+begin
+  SetPrecisionMode(pmDouble);
+  offsetMomentum;
+  writeln(energy:0:9);
+  Val(ParamStr(1), n, i);
+  for i := 1 to n do advance(0.01);
+  writeln(energy:0:9);
+end.