Thread: Mutidimensional Array problem

Code:

  int N, i = 0, j = 0, trial, to = 0, dis = 0, maxstep = 0, nstep = 0;
  double tao, tau, dx, counter = 0, u = 0, a = 0, dt = 0, t = 0, g = 0;
  double *array, *b;

printing to file.stderr to have a look in the another file instead of under terminal, but that is not necessary.

Code:

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include <gsl/gsl_rng.h>
#include <gsl/gsl_randist.h>

int main(int argc, char *argv[])
{
  int N, i = 0, j = 0, trial, to = 0, dis = 0, maxstep = 0, nstep = 0;
  double tao, tau, dx, counter = 0, u = 0, a = 0, dt = 0, t = 0, g = 0;
  double *array, *b; 
  
  if(argc != 7)
    {
      printf("Error!\nUsage: N(int), tao(double), a(double), dx(double), to(int), g(double)\n");
      return 0;
    }
  else
    {
      sscanf( argv[1], "%d", &N);
    }
  sscanf( argv[2], "%lf", &tao);
  sscanf( argv[3], "%lf", &a);
  sscanf( argv[4], "%lf", &dx);
  sscanf( argv[5], "%d", &to);
  sscanf( argv[6], "%lf", &g);

  tau = tao * (1 + g * t);
  dt = -log(a) * tau;
  
  const gsl_rng_type * T;
  gsl_rng * r;
  
  gsl_rng_env_setup();
  
  T = gsl_rng_default;
  r = gsl_rng_alloc (T);
  gsl_rng_set (r, time(NULL));

  array = (double*) malloc (to * to * sizeof(double));

  for(i = 0; i < to * to; i++)
    {
      array[i] = 0.0;      
    }

  while(t < to)
    {
      tau = tao * (1 + g * t);
      dt = -log(a) * tau;
      t = t + dt;
      nstep++;
    }
  maxstep = nstep;

  b = (double *) malloc (maxstep * maxstep * sizeof(double));
  
  for(trial = 0; trial < N; trial++)
    {
      b[trial] = 0.0;
      nstep = 0;
      t = 0.0;
      dis = 0;
      counter = 0;
      while(t < to)
	{
	  tau = tao * (1 + g * t);
	  dt = -log(a) * tau;
	  u = gsl_ran_flat (r, 0.0, 1.0);
	  b[nstep * maxstep + dis]++;
	  if(u > a)
	    {
	      dis++;
	    }
	  t = t + dt;
	  nstep++;
	}
    }
  
  for(i = 0; i < maxstep; i++)
    {
      for(j = 0; j < maxstep; j++)
	{
	  fprintf(stderr, "%lf ", b[j * maxstep + i]);
	}
	  fprintf(stderr, "\n");
    }
  free(array);
  free(b);
  return 0;
}

This is a simulation of particle hopping in one dimension. maybe it's easier for you to look at then for me to explain, essentially, I need to print out b(i,j) which stores the number of particles which were at position j after i steps out of all N trials. This is used at the end to calculate the average position after i steps.

Thanks, but could you explain to me why my two columns don't sum up to 20 respectively? I run 20 trials, so it should have a registered position for every step of the 20 trials. The table is of steps(X) * position(Y).

The code is working fine, there are some malfunctions in the results, or it could be that I'm misinterpreting it.

I'm running 20 trials.
Each particle has a position after a certain steps.
The columns represents all the particles at step 1 ( or 2 or 3...etc)
The rows represents where the parctiel is at step 1 (or 2 or 3...etc)

Code:

20.000000 3.000000 0.000000 3.000000 2.000000 1.000000 0.000000 0.000000 
0.000000 8.000000 0.000000 6.000000 4.000000 3.000000 3.000000 2.000000 
0.000000 0.000000 2.000000 9.000000 8.000000 3.000000 2.000000 2.000000 
0.000000 0.000000 0.000000 2.000000 4.000000 8.000000 7.000000 4.000000 
0.000000 0.000000 0.000000 0.000000 2.000000 4.000000 4.000000 7.000000 
0.000000 0.000000 0.000000 0.000000 0.000000 1.000000 3.000000 2.000000 
0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 1.000000 2.000000 
0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 1.000000

at (0,0), all 20 particles are at position 0 because it's the initial position, ie. step 0.
at (0,1), it shows that there are 3 particles at position 0 at step 1.
at (1,1), it shows that there are 8 particles at position 1 at step 1.

etc.

So shouldn't there be 20 particles at step 1, regardless of their position? (there are only 8+3 = 11)

Code:

    b[trial] = 0.0;

That's not supposed to be there, instead there should have been a loop that initializes all the b values. =) I just found that out.

Code:

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include <gsl/gsl_rng.h>
#include <gsl/gsl_randist.h>

int main(int argc, char *argv[])
{
  int N, i = 0, j = 0, trial, to = 0, dis = 0, maxstep = 0, nstep = 0;
  double tao, tau, dx, counter = 0, u = 0, a = 0, dt = 0, t = 0, g = 0;
  double *array, *b, *times; 
  
  if(argc != 7)
    {
      printf("Error!\nUsage: N(int), tao(double), a(double), dx(double), to(int), g(double)\n");
      return 0;
    }
  else
    {
      sscanf( argv[1], "%d", &N);
    }
  sscanf( argv[2], "%lf", &tao);
  sscanf( argv[3], "%lf", &a);
  sscanf( argv[4], "%lf", &dx);
  sscanf( argv[5], "%d", &to);
  sscanf( argv[6], "%lf", &g);

  tau = tao * (1 + g * t);
  dt = -log(a) * tau;
  
  const gsl_rng_type * T;
  gsl_rng * r;
  
  gsl_rng_env_setup();
  
  T = gsl_rng_default;
  r = gsl_rng_alloc (T);
  gsl_rng_set (r, time(NULL));

  array = (double*) malloc (to * to * sizeof(double));

  for(i = 0; i < to * to; i++)
    {
      array[i] = 0.0;      
    }

  while(t < to)
    {
      tau = tao * (1 + g * t);
      dt = -log(a) * tau;
      t = t + dt;
      nstep++;
    }
  maxstep = nstep;

  b = (double *) malloc (maxstep * maxstep * sizeof(double));
  times = (double *) malloc (maxstep *sizeof(double));
 
  for(i = 0; i < maxstep * maxstep; i++)
    {
      b[i] = 0.0;
    }
  
  for(trial = 0; trial < N; trial++)
    {
      nstep = 0;
      t = 0.0;
      dis = 0;
      counter = 0.0;
      while(t < to)
	{
	  tau = tao * (1 + g * t);
	  dt = -log(a) * tau;
	  u = gsl_ran_flat (r, 0.0, 1.0);
	  b[nstep * maxstep + dis]++;
	  if(u > a)
	    {
	      dis++;
	    }
	  t = t + dt;
	  nstep++;
	  times[nstep] = t; //Segmentation Fault...why?
	  counter = counter + nstep * b[nstep * maxstep + dis]/N;
	  fprintf(stdout, "%f %f\n", times[nstep], counter);
	}
    }
  
  for(i = 0; i < maxstep; i++)
    {
      for(j = 0; j < maxstep; j++)
	{
	  fprintf(stderr, "%lf ", b[j * maxstep + i]);
	}
	  fprintf(stderr, "\n");
    }
  free(array);
  free(b);
  return 0;
}

*bump*

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