#include <stdio.h>

#define SIZE 1000000
#define X  2*((SIZE-1) / 2) + 1
#define T 10000000

int binsearch(int x, int v[], int n);
int binsearch_old(int x, int v[], int n);

/* run binsearch on array of size SIZE
 * if arg is provided use old binsearch */
int main(int argc, char *argv[])
{
    long i;
    int arr[SIZE];

    for (i = 0; i < SIZE; ++i)
        arr[i] = 2 * i;

    if (argc == 1) {
        for (i = 0; i < T; ++i)
            binsearch(X, arr, SIZE);
        printf("binsearch : %d\n", binsearch(X, arr, SIZE));
    }
    else {
        for (i = 0; i < T; ++i)
            binsearch_old(X, arr, SIZE);
        printf("old binsearch : %d\n", binsearch_old(X, arr, SIZE));
    }
    return 0;
}

/* binsearch: find x in sorted v of length n, using one comparison in loop */
int binsearch(int x, int v[], int n)
{
    int low, high, mid;

    low = 0;
    high = n - 1;
    while (low < high) {
        mid = (low + high) / 2;
        if (x <= v[mid])
            high = mid;
        else
            low  = mid + 1;
    }
    if (v[low] == x)
        return low;
    return -1;
}

/* binsearch: find x in sorted v of length n, using two comparisons in loop */
int binsearch_old(int x, int v[], int n)
{
    int low, high, mid;

    low = 0;
    high = n - 1;
    while (low <= high) {
        mid = (low + high) / 2;
        if (x < v[mid])
            high = mid - 1;
        else if (x > v[mid])
            low  = mid + 1;
        else
            return mid;
    }
    return -1;
}