Ticket #169: test_conversion.c

/* 
 * Small script to test whether or not multiplying an integer with a
 * floating point number and back changes the integer
 */

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

main(){
   
    // Variables to count the iterations. Loop over all integers from
    // i to max_i.
    int i = 0;
    int max_i = 200000;

    // How many floats should be tested per integer.
    int number_of_floats = 100000;
    // The range of the floating point numbers.
    float min_float = 0.00001;
    float max_float = 100000.0;
    float range = max_float - min_float;
    // Once again because small numbers might cause more problems.
    float small_min_float = 0.00001;
    float small_max_float = 1.0;
    float small_range = small_max_float - small_min_float;

    // Keep count.
    long absolute_error_count = 0;
    long absolute_sample_count = 0;

    // Generate a random number seed based on the time to get different results every time.
    srand(time(NULL));

    // Loop over all integer values.
    while (i<max_i){

        // Only print all 1000 values.
        if (i%1000 == 0){
                printf("Current Integer: %i of %i\n", i, max_i);
        }

        int current_errors = 0;
        int current_count = 0;

        // Loop over random floating point values for every integer.
        int j = 1;
        while (j < number_of_floats){
                // Get the random float normalized between 0 and 1 and scale
                // accordingly.
                float random_float = (float)rand()/(float)RAND_MAX;
                random_float = min_float + random_float * range;
                // Convert integer to floating point.
                float float_i = i * random_float;
                float_i /= random_float;
                // Round to avoid errors.
                float_i = round(float_i);
                // Convert back to integers.
                int int_i = (int) float_i;
                // Check if anything changed.
                if (int_i != i){
                        absolute_error_count += 1;
                }

                // Again for the very small numbers.
                random_float = (float)rand()/(float)RAND_MAX;
                random_float = small_min_float + random_float * small_range;
                // Convert integer to floating point.
                float_i = i * random_float;
                float_i /= random_float;
                // Round to avoid errors.
                float_i = round(float_i);
                // Convert back to integers.
                int_i = (int) float_i;
                // Check if anything changed.
                if (int_i != i){
                        absolute_error_count += 1;
                }
                absolute_sample_count += 2;

                // Increment.
                j += 1;
        }

        i += 1;
    }
    double relative = ((double) absolute_error_count) / ((double) absolute_sample_count);
    printf("\n\n===============\nFinal result:\n\tSamples: %li\nErrors: %li (%.3f %%)\n\n", absolute_sample_count, absolute_error_count, relative);
}