Optimizing Polynomial Function: Gorner Algorithm

//
//  Gorner's algorithm test
//
//  See explanation at: http://joydevel.blogspot.com/2012/07/blog-post_05.html
//

#include <stdio.h>
#include <sys/time.h>
#include <math.h>

#define number float

number
polynom (number*a, unsigned int a_length, number x)
{
    number b = a[0];
    for (int i = 1; i < a_length; i++)
    {
        b += a[i]*pow(x, i);
    }
    return b;
}

number
gorner_recursive (number* a, unsigned int a_length, number x, unsigned int i)
{
    if (i > a_length - 1) return 0;
    return a[i] + x * gorner_recursive(a, a_length, x, i + 1);
}

number
gorner_normal (number* a, unsigned int a_length, number x)
{
    number b = a[a_length - 1];
    for (int i = a_length - 2; i >= 0; i--)
    {
        b = a[i] + x * b;
    }
    return b;
}

int
main(int argc, const char * argv[])
{
    #define COEFFS_LENGTH 1000

    number a[COEFFS_LENGTH];
    {
        for (int i = 0; i < COEFFS_LENGTH; i++)
        {
            a[i] = i * 0.2f;
        }
    }

    number x = .1f;

    number normal;
    number recursive;
    number common;

    struct timeval t_start;
    gettimeofday(&t_start, NULL);

    for (int i = 0; i < 1E2; i++)
    {
        normal = gorner_normal(a, COEFFS_LENGTH, x);
    }

    struct timeval t_normal;
    gettimeofday(&t_normal, NULL);

    for (int i = 0; i < 1E2; i++)
    {
        recursive = gorner_recursive(a, COEFFS_LENGTH, x, 0);
    }

    struct timeval t_recursive;
    gettimeofday(&t_recursive, NULL);

    for (int i = 0; i < 1E2; i++)
    {
        common = polynom(a, COEFFS_LENGTH, x);
    }

    struct timeval t_common;
    gettimeofday(&t_common, NULL);

    printf("Results:\n normal %f\n recursive %f\n common %f\n", normal, recursive, common);
    printf("Time consumption:\n normal %i\n recursive %i\n common %i\n",
           t_normal.tv_usec - t_start.tv_usec,
           t_recursive.tv_usec - t_normal.tv_usec,
           t_common.tv_usec - t_recursive.tv_usec
           );

    return 0;
}