N-ary search program in C using openmp is giving error when thread count is less than 4

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This is program for n-ary search . When we give no. of threads less than 4 , it says core dumped (Segmentation fault).But if thread count is 4 or more than 4 it works successfully giving reults. CODE::

#include<stdio.h>
#include<omp.h>
//#include<timer.h>
int a[65536],s,test;
int global_size,global_x,n;

void nary_search(int,int);
main()
{
    int i,size=65536,x=0;

    for(i=0;i<size;i++)
    a[i]=i;
    printf("Enter number to be searched\n");
    scanf("%d",&s);
    printf("enter the number of threads used\n");
    scanf("%d",&n);


    nary_search(size,x);




}



void nary_search(int size,int x)
{
    printf("size = %d\n",size);
    if(size<=n)
    {

        test=0; 
        #pragma omp parallel
        {
            int tid=omp_get_thread_num();
            if(a[global_x+tid]==s)
            {

                printf("found at %d\n",global_x+tid);
                test=1;
            }
        }

        if(test==0)
        {

            printf("not found\n");
        }
    }
    else
    {
        test=0;
        #pragma omp parallel 
        {
            int tid=omp_get_thread_num();
            printf("checking (%d --  %d)with thread %d on cpu %d \n",a[tid*size/n+x],a[tid*size/n+size/n-1+x],tid,sched_getcpu());  
            if(s>=a[tid*size/n+x] && s<=a[tid*size/n+size/n-1+x])
            {
                printf("may be here  %d ---- %d  size=(   %d   )\n",a[tid*size/n+x],a[tid*size/n+size/n-1+x],+size/n);
                global_size=size/n;             
                global_x=tid*global_size+x;
                test=1;
            }
        }
        if(test==1)
            nary_search(global_size,global_x);
        else
            printf("not found in");
    }
}

Can anybody help with this error ?

asked 30 secs ago

Ishwar .Patil

57

N-ary search program in C using openmp is giving error when thread count is less than 4