Created
December 22, 2014 06:45
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#include <iostream> | |
#include <stdlib.h> | |
#include <stdio.h> | |
#include <sys/time.h> | |
//---------------------------------------------------------------------- | |
const int N = 20000; | |
const double L = 10.0; | |
const int D = 3; | |
const int X = 0; | |
const int Y = 1; | |
const int Z = 2; | |
double q[D][N],p[D][N]; | |
const double dt = 0.001; | |
const double C2 = 0.1; | |
const double CUTOFF2 = L*L*0.9*0.9; | |
//---------------------------------------------------------------------- | |
double | |
myrand(void){ | |
return static_cast<double>(rand())/(static_cast<double>(RAND_MAX)); | |
} | |
//---------------------------------------------------------------------- | |
double | |
myclock(void){ | |
struct timeval t; | |
gettimeofday(&t, NULL); | |
return t.tv_sec + t.tv_usec*1e-6; | |
} | |
//---------------------------------------------------------------------- | |
void | |
calcforce(void){ | |
for(int i=0;i<N-1;i++){ | |
for(int j=i+1;j<N;j++){ | |
double dx = q[X][j] - q[X][i]; | |
double dy = q[Y][j] - q[Y][i]; | |
double dz = q[Z][j] - q[Z][i]; | |
double r2 = (dx*dx + dy*dy + dz*dz); | |
double r6 = r2*r2*r2; | |
double df = ((24.0*r6-48.0)/(r6*r6*r2)+C2*8.0)*dt; | |
p[X][i] += df*dx; | |
p[Y][i] += df*dy; | |
p[Z][i] += df*dz; | |
p[X][j] -= df*dx; | |
p[Y][j] -= df*dy; | |
p[Z][j] -= df*dz; | |
} | |
} | |
} | |
//---------------------------------------------------------------------- | |
void | |
measure(void(*pfunc)(),const char *name){ | |
double st = myclock(); | |
pfunc(); | |
double t = myclock()-st; | |
printf("N=%d, %s %f [sec]\n",N,name,t); | |
} | |
//---------------------------------------------------------------------- | |
int | |
main(void){ | |
for(int i=0;i<N;i++){ | |
p[X][i] = 0.0; | |
p[Y][i] = 0.0; | |
p[Z][i] = 0.0; | |
q[X][i] = L*myrand(); | |
q[Y][i] = L*myrand(); | |
q[Z][i] = L*myrand(); | |
} | |
measure(&calcforce,"calcforce"); | |
} | |
//---------------------------------------------------------------------- |
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