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added softening

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This commit is contained in:
Evghenii
2014-02-21 14:18:29 +01:00
parent f09c74db21
commit 259bb81b1e
2 changed files with 20 additions and 8 deletions
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7
examples/portable/nbody_hermite4/hermite4.cpp
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@@ -20,6 +20,7 @@ struct Hermite4
enum {PP_FLOP=44}; enum {PP_FLOP=44};
const int n; const int n;
const real eta; const real eta;
real eps2;
real *g_mass, *g_gpot; real *g_mass, *g_gpot;
real *g_posx, *g_posy, *g_posz; real *g_posx, *g_posy, *g_posz;
real *g_velx, *g_vely, *g_velz; real *g_velx, *g_vely, *g_velz;
@@ -31,6 +32,8 @@ struct Hermite4
Hermite4(const int _n = 8192, const real _eta = 0.1) : n(_n), eta(_eta) Hermite4(const int _n = 8192, const real _eta = 0.1) : n(_n), eta(_eta)
{ {
eps2 = 4.0/n; /* eps = 4/n to give Ebin = 1 KT */
eps2 *= eps2;
g_mass = new real[n]; g_mass = new real[n];
g_gpot = new real[n]; g_gpot = new real[n];
g_posx = new real[n]; g_posx = new real[n];
@@ -289,7 +292,8 @@ void Hermite4::forces()
g_jrkx, g_jrkx,
g_jrky, g_jrky,
g_jrkz, g_jrkz,
g_gpot); g_gpot,
eps2);
} }
void run(const int nbodies, const real eta, const int nstep) void run(const int nbodies, const real eta, const int nstep)
@@ -312,6 +316,7 @@ int main(int argc, char *argv[])
if (argc > 3) eta = atof(argv[3]); if (argc > 3) eta = atof(argv[3]);
printf("nbodies= %d\n", nbodies); printf("nbodies= %d\n", nbodies);
printf("nstep= %d\n", nstep); printf("nstep= %d\n", nstep);
printf(" eta= %g \n", eta); printf(" eta= %g \n", eta);

21
examples/portable/nbody_hermite4/hermite4.ispc
View File

@@ -17,15 +17,20 @@ void body_body_force(
Force &fi, Force &fi,
const Predictor &pi, const Predictor &pi,
const Predictor &pj, const Predictor &pj,
const real mj) const real mj,
const real eps2)
{ {
const real dx = pj.pos.x - pi.pos.x; const real dx = pj.pos.x - pi.pos.x;
const real dy = pj.pos.y - pi.pos.y; const real dy = pj.pos.y - pi.pos.y;
const real dz = pj.pos.z - pi.pos.z; const real dz = pj.pos.z - pi.pos.z;
const real ds2 = dx*dx + dy*dy + dz*dz; const real ds2 = dx*dx + dy*dy + dz*dz + eps2;
const real inv_ds = ds2 > 1.0d-10 ? rsqrt((float)ds2) : 0.0; #if 1
const real inv_ds = rsqrt((float)ds2);
#else
const real inv_ds = rsqrt(ds2);
#endif
const real inv_ds2 = inv_ds*inv_ds; const real inv_ds2 = inv_ds*inv_ds;
const real minv_ds = inv_ds * mj; const real minv_ds = inv_ds * mj;
const real minv_ds3 = inv_ds2 * minv_ds; const real minv_ds3 = inv_ds2 * minv_ds;
@@ -64,7 +69,8 @@ task void compute_forces_task(
uniform real jrkx[], uniform real jrkx[],
uniform real jrky[], uniform real jrky[],
uniform real jrkz[], uniform real jrkz[],
uniform real gpot[]) uniform real gpot[],
const uniform real eps2)
{ {
const uniform int nibeg = taskIndex * nPerTask; const uniform int nibeg = taskIndex * nPerTask;
const uniform int niend = min(n, nibeg + nPerTask); const uniform int niend = min(n, nibeg + nPerTask);
@@ -112,7 +118,7 @@ task void compute_forces_task(
pj.vel.y = shdata[5][j]; pj.vel.y = shdata[5][j];
pj.vel.z = shdata[6][j]; pj.vel.z = shdata[6][j];
const real jmass = shdata[3][j]; const real jmass = shdata[3][j];
body_body_force(fi,pi,pj,jmass); body_body_force(fi,pi,pj,jmass,eps2);
} }
} }
@@ -141,7 +147,8 @@ export void compute_forces(
uniform real jrkx[], uniform real jrkx[],
uniform real jrky[], uniform real jrky[],
uniform real jrkz[], uniform real jrkz[],
uniform real gpot[]) uniform real gpot[],
const uniform real eps2)
{ {
const uniform int nPerTask = min(128,programCount*8); const uniform int nPerTask = min(128,programCount*8);
const uniform int nTask = (n+nPerTask-1)/nPerTask; const uniform int nTask = (n+nPerTask-1)/nPerTask;
@@ -153,5 +160,5 @@ export void compute_forces(
velx,vely,velz, velx,vely,velz,
accx,accy,accz, accx,accy,accz,
jrkx,jrky,jrkz, jrkx,jrky,jrkz,
gpot); gpot,eps2);
} }