Program does not execute anything when it enters function

Question

My program runs, but right after asking for the value prob() the .exe stop working.

I thought it was some communication problem between functions on account of the matrix lattice[][4] as an argument, but I have already searched, set up and the same thing keeps happening. I am almost sure that the problem lies in the communication between the main() and the label().

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int random();
float prob();
int label(float lattice[][4],float);
int i, j;

int random()   /* Sorteia um número entre de 0 a 1 */
{
    float x;
    srand((unsigned)time(NULL));
    x = rand()%100+1;
    x = x/100;
    return x;
}

float prob()
{
    float p;
    printf("Probabilidade: ");
    scanf("%f", &p);
    return p;
}

int label(float lattice[][4], float p)
{

for(i=0; i<4 ; i++)
    for(j=0; j<4; i++)
    {
        lattice[i][j] = random();   
    }

for(i=0; i<4; i++)
    for(j=0; j<4; j++)
    {
        if(lattice[i][j] <= p)      
            lattice[i][j] = 1;
        else
            lattice[i][j] = 0;
    }
return 0;
}

int main()
{
     float lattice[4][4];
     float p = prob();
     label(lattice, p);
     system("pause");
     return 0;
}

Answer 1

The error is that you are incrementing the second loop with the wrong variable:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int random() {
    float x;
    srand((unsigned)time(NULL));
    x = rand() % 100 + 1;
    x = x / 100;
    return x;
}

float prob() {
    float p;
    printf("Probabilidade: ");
    scanf("%f", &p);
    return p;
}

int label(float lattice[][4], float p) {
    for (int i = 0; i < 4 ; i++)
        for (int j = 0; j < 4; j++) lattice[i][j] = random();
    for (int i = 0; i < 4; i++)
        for (int j = 0; j < 4; j++) {
            if (lattice[i][j] <= p) lattice[i][j] = 1;
            else lattice[i][j] = 0;
        }
    return 0;
}

int main() {
    float lattice[4][4];
    float p = prob();
    label(lattice, p);
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

Note that I improved the code a little. It would still be cool to use keys even where you don’t need them. Even because it is already used in some places, so maintain consistency. This is very important in programming.

When so, isolate the problem, print the value of the variables step by step or use a tool debug that will show to you. Seeing the program run is the way to find the problem. That’s basically what I did to find the problem, so I needed the code in order to compile.