Pointers, Arrays, Assigning values

[Iconate]

I have zero idea why this is occuring, I have looked at so many examples of pointers and arrays and I just cannot figure this out.

All I am trying to do right now is create an n by m matrix and populate it with random numbers...but all I get are null pointers (ie 0)

#include <stdio.h>
#include <stdlib.h>
#include "mpi.h"

int main(int argc, char* argv[]){
        int rank;
        int p;
        int i, j;

        double *A;              //Matrix A
        double *b;              //Vector b

        int m = atoi(argv[1]);
        int n = atoi(argv[2]);

        //printf("M=%d, N=%d\n", m,n);  //Strictly used for testing purposes

        A = malloc((n*m)*sizeof(double));

        for (i=0; i<n; i++){
                for(j=0; j<n; j++){
                        A[i*n + j] =  rand() % 100;//assigns *A random numbers between 0 - 99
                        printf("%d\n",A[i*n +j]);
                }
        }

        //genMatrix(n, m, A);
        /*
        MPI_Init(&argc, &argv);
        MPI_Comm_rank(MPI_COMM_WORLD, &rank);
        MPI_Comm_size(MPI_COMM_WORLD, &p);
        MPI_Finalize();
        */

        return 0;
}

I even tried writing

double *A;
...
A = malloc((n*m)*sizeof(double);
...
A[0] = 5;
printf("%d", A[0]);

And this is returning 0, rather, a null pointer as well. Any help would be greatly appreciated

[msh]

srand() before calling rand() and:

for(j=0; j<n; j++);  // change to: for (j = 0; j < m; j++);

[Iconate]

I found the solution to my error...

I am supposed to use %.1f....not %d

>.<

[Salem]

If you're using gcc as your compiler, then seriously consider adding at least -Wall as a command line option.

One of the many things it can diagnose is mis-matched printf/scanf formats.