#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <unistd.h>
#include <omp.h>



void qsort_parallel(unsigned *a,int l,int r){
    if(r>l){

        int pivot=a[r],tmp;
        int less=l-1,more;
        for(more=l;more<=r;more++){
            if(a[more]<=pivot){
                less++;
                tmp=a[less];
                a[less]=a[more];
                a[more]=tmp;
            }
        }
            #pragma omp task
            qsort_parallel(a, l,less-1);
            #pragma omp task
            qsort_parallel(a, less+1,r);
            #pragma omp taskwait
    }
}

void readFileUnsigned(unsigned *input, char *filename, int size) {
    FILE *finput;
    if (finput = fopen(filename, "rb")) {
        fread(input, size * sizeof(unsigned), 1 , finput);
    } else {
        printf("Error reading input file");
        exit(1);
    }
}
int main(int argc, char** argv)
{
    int size, omp_num_threads, iterations;
    char * inputFile, *outputFile;
    unsigned *data;

    if (argc == 5) {
        size = atoi(argv[1]);
        omp_num_threads = atoi(argv[2]);
        inputFile = argv[3];
        outputFile = argv[4];
    } else {
        fprintf(stderr, "Usage: %s <input size> <num_threads> <input file> <output file>\n", argv[0]);
        exit(1);
    }

    omp_set_num_threads(omp_num_threads);

    data = (unsigned *)malloc(size*sizeof(unsigned));

    readFileUnsigned(data, inputFile, size);

    #pragma omp parallel
    #pragma omp single
    qsort_parallel(data, 0,size-1);

    FILE *fp;
    if (fp = fopen(outputFile, "wb")) {
        fwrite(data, size * sizeof(unsigned), 1 , fp);
    } else {
        printf("Error writing output file");
        exit(1);
    }
    fclose(fp);

    printf("Done\n");

    return 0;
}