Thread: Parallel programming : Game of Life.

Can someone help me fix my code. It is supposed to stop after 2 iterations that are the same. All it does stop after 2 iterations.

Attachments are code and pic of the input file.

Code:

#include <stdio.h>
#include <string.h>
#include <omp.h>
#include <stdlib.h>
#include <assert.h>
#define MAX_N 2000

int plate[2][(MAX_N + 2) * (MAX_N + 2)];
int which = 0;
int n;


int live(int index)
{
    return (plate[which][index - n - 3] + plate[which][index - n - 2] + plate[which][index - n - 1]
    + plate[which][index - 1] + plate[which][index + 1] + plate[which][index + n + 1]
    + plate[which][index + n + 2] + plate[which][index + n + 3]);
}

int iteration() // specifying return-type as int
{
    // variable change is initialized to 0, indicating there's no change in plate till now. This variable is returned at the end of the function
    int change = 0; 
    #pragma omp parallel for schedule(static)
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n; j++)
        {
            int index = i * (n + 2) + j;
            int num = live(index);
            int prevStatus = plate[!which][index]; //Storing the previous Status of the row and column of the plate which is to be evaluated.
            if(plate[which][index])
            {
                plate[!which][index] = (num == 2 || num == 3) ? 1 : 0;
            }
            else
            {
                plate[!which][index] = (num == 3);
            }
            if(prevStatus==plate[!which][index]) // After evaluation of a particular row and column of the plate it checking if the previous Status is same as the new Status and if it is new then changing the variable change to 1, indicating the plate is changed
            {
                change = 1;
            }
        }
    }
    which = !which;
    return change; //Return change
}

void print_plate()
{
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n; j++)
        {
            printf("%d", plate[which][i * (n + 2) + j]);
        }
        printf("\n");
    }
    printf("\0");
}

int main()
{

    double start, finish;
    //start = omp_get_wtime();
    int M;
    char line[MAX_N];
    memset(plate[0], 0, sizeof(int) * (n + 2) * (n + 2));
    memset(plate[1], 0, sizeof(int) * (n + 2) * (n + 2));
    
    if(scanf("%d %d", &n, &M) == 2)
    {
        for(int i = 1; i <= n; i++)
        {
            scanf("%s", &line);
            for(int j = 0; j < n; j++)
            {
                plate[0][i * (n + 2) + j + 1] = line[j] - '0';
            }
        }
        printf("Initial Configuration \n");
        print_plate();
        printf("\n");
        int count = 0; //A new count variable is initialized with 0, indicating there's been 0 changes consecutively.
        
        for(int i = 0; i < M; i++)
        {
            int change = iteration(); //Storing the return value of iteration to variable change
            if(change==1) //If change is occurred then increase the count value by 1
            {
                count++;
            }
            else
            {
                count = 0; //If no change occurred in the plate then again reassign count to 0.
            }
            if(count==2) //Check if count reaches 2, if it does then add break statement to come out of loop
                break;
            printf("Generation: %d", i);
            printf("\n");
            print_plate();
            printf("\n");
        }
        printf("Last Generation.\n");
        print_plate();
        //finish = omp_get_wtime();
        //printf("Time: \t %f \n", finish - start);
    }
    return 0;
}

life_test.c

You're using n before it's initialized. This shouldn't be a problem, though, since you're writing over the array anyway and on a modern compiler that should be 0 even if it's "uninitialized" memory. Those memsets don't do anything if n is 0.

Line 77 you're passing &line when you mean line. There absolutely should be a compiler warning about this. Do not ignore warnings. Again, you dodged a bullet because in this case &line and line are the same thing, just a different type.

Line 59 does nothing at all. You're printing an empty string. Did you mean to print \n?

But the real reason why this doesn't work is line 99. You're explicitly breaking when you hit 2 generations with changes. Oh, and line 39, don't you mean !=? If the previous state is not equal to the new state, then set changed. Ultimately, most simulations will never end for you like this though. If there's just one blinker on the field then it will go on forever.

You also seem to be using the border trick to do wrapping, but where are you initializing the border? I would really work on getting the basics of this working before you start trying to add parallelism into the mix.