#include "defs.h"

double get_seconds() {
    struct timeval tp;
    gettimeofday(&tp, NULL);
    return (double) (tp.tv_sec + ((1e-6)*tp.tv_usec));
}

void prefix_sums(LONG_T *input, LONG_T* result, LONG_T* p, LONG_T n) {
    
    LONG_T i;
    
#ifdef _OPENMP
    LONG_T j, r, start, end, add_value;
    int tid, nthreads;

    tid = omp_get_thread_num();
    nthreads = omp_get_num_threads();
    r = n/nthreads;

    result[0] = 0;

    #pragma omp for
    for (i=1; i<n+1; i++)
        result[i] = input[i-1];

    start =  tid*r + 1;
    end   = (tid+1)*r;

    if (tid == nthreads-1)
        end = n+1;

    for (j=start; j<end; j++)
        result[j] = input[j-1] + result[j-1];

    p[tid] = result[end-1];

    #pragma omp barrier

    if (tid == 0) {
        for (j=1; j<nthreads; j++)
            p[j] += p[j-1];
    }

    #pragma omp barrier

    if (tid>0) {
        add_value=p[tid-1];
        for (j=start-1; j<end; j++)
            result[j] += add_value;
    }

#else

    result[0] = 0;
    for (i=1; i<n+1; i++) {
        result[i] = result[i-1] + input[i-1];
    }

#endif
    
}