random.c

/* random.c */
#include <stdio.h>
#include <time.h>
#include <stdlib.h>

void parser(char *input, double particles[][4]){
  sscanf(
    input, 
    "p[20] = nullvector(%lf,%lf,%lf,%lf)", 
    &particles[20][3], &particles[20][0],
    &particles[20][1], &particles[20][2]
  );

  printf(
    "energy: %E, p: (%E, %E, %E)\n",
    particles[20][3], particles[20][0],
    particles[20][1], particles[20][2]
  );
}

int main(){
  double particles[22][4];
  int seed,i,x,y;
  double px_buf, py_buf, pz_buf;

  seed=time(NULL);
  srand(seed);

  /* The random numbers are generated between 1E-12 and 10E-12 */
  /*Double precision floats support up to 15 decimal places*/
  for(i=0;i<20;i++){
    px_buf=((double)rand()/RAND_MAX)*9001E-15;
    py_buf=((double)rand()/RAND_MAX)*9001E-15;
    pz_buf=((double)rand()/RAND_MAX)*9001E-15;
    particles[0][i]=px_buf;
    particles[1][i]=py_buf;
    particles[2][i]=pz_buf;
    printf("(step: %i) The following noise momentum was generated: (%.15E,%.15E,%.15E)\n",i,px_buf,py_buf,pz_buf);
  }


  parser("p[20] = nullvector(45.0000000000106,33.03951484238976,14.97124733712793,26.6317895033428)", \
      particles);

  for(y=0;y<22;y++){
    for(x=0;x<3;x++){
      printf("%.15E \t", particles[x][y]);
    }
    printf("\n");
  }
  return 0;
}