sintest.c

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

#include "src/utils/math.h"

// Sine lookup table for the range [0..180].
const float sin_table[] = {
    0.0,
    0.01745240643728351, 0.03489949670250097, 0.052335956242943835,
    0.0697564737441253, 0.08715574274765817, 0.10452846326765347,
    0.12186934340514748, 0.13917310096006544, 0.15643446504023087,
    0.17364817766693033, 0.1908089953765448, 0.20791169081775934,
    0.224951054343865, 0.24192189559966773, 0.25881904510252074,
    0.27563735581699916, 0.29237170472273677, 0.3090169943749474,
    0.3255681544571567, 0.3420201433256687, 0.35836794954530027,
    0.374606593415912, 0.39073112848927377, 0.4067366430758002,
    0.42261826174069944, 0.4383711467890774, 0.45399049973954675,
    0.4694715627858908, 0.48480962024633706,
    0.5,
    0.5150380749100542, 0.5299192642332049, 0.5446390350150271,
    0.5591929034707469, 0.573576436351046, 0.5877852522924731,
    0.6018150231520483, 0.6156614753256583, 0.6293203910498374,
    0.6427876096865393, 0.6560590289905073, 0.6691306063588582,
    0.6819983600624985, 0.6946583704589973, 0.7071067811865475,
    0.7193398003386511, 0.7313537016191705, 0.7431448254773942,
    0.7547095802227719, 0.766044443118978, 0.7771459614569708,
    0.7880107536067219, 0.7986355100472928, 0.8090169943749473,
    0.8191520442889917, 0.8290375725550416, 0.838670567945424,
    0.848048096156426, 0.8571673007021123, 0.8660254037844386,
    0.8746197071393957, 0.8829475928589269, 0.8910065241883678,
    0.898794046299167, 0.9063077870366499, 0.9135454576426009,
    0.9205048534524404, 0.9271838545667874, 0.9335804264972017,
    0.9396926207859083, 0.9455185755993167, 0.9510565162951535,
    0.9563047559630354, 0.9612616959383189, 0.9659258262890683,
    0.9702957262759965, 0.9743700647852352, 0.9781476007338056,
    0.981627183447664, 0.984807753012208, 0.9876883405951378,
    0.9902680687415704, 0.992546151641322, 0.9945218953682733,
    0.9961946980917455, 0.9975640502598242, 0.9986295347545738,
    0.9993908270190958, 0.9998476951563913,
    1.0,
    0.9998476951563913, 0.9993908270190958, 0.9986295347545738,
    0.9975640502598242, 0.9961946980917455, 0.9945218953682733,
    0.9925461516413221, 0.9902680687415704, 0.9876883405951378,
    0.984807753012208, 0.981627183447664, 0.9781476007338057,
    0.9743700647852352, 0.9702957262759965, 0.9659258262890683,
    0.9612616959383189, 0.9563047559630355, 0.9510565162951536,
    0.9455185755993168, 0.9396926207859084, 0.9335804264972017,
    0.9271838545667874, 0.9205048534524403, 0.9135454576426009,
    0.90630778703665, 0.8987940462991669, 0.8910065241883679,
    0.8829475928589269, 0.8746197071393959, 0.8660254037844388,
    0.8571673007021123, 0.8480480961564261, 0.838670567945424,
    0.8290375725550418, 0.8191520442889917, 0.8090169943749475,
    0.7986355100472928, 0.788010753606722, 0.7771459614569711,
    0.7660444431189781, 0.7547095802227721, 0.7431448254773942,
    0.7313537016191707, 0.7193398003386511, 0.7071067811865476,
    0.6946583704589971, 0.6819983600624985, 0.6691306063588583,
    0.6560590289905073, 0.6427876096865395, 0.6293203910498374,
    0.6156614753256584, 0.6018150231520482, 0.5877852522924732,
    0.5735764363510459, 0.5591929034707469, 0.5446390350150273,
    0.5299192642332049, 0.5150380749100544,
    0.5,
    0.48480962024633717, 0.4694715627858907, 0.45399049973954686,
    0.4383711467890773, 0.4226182617406995, 0.40673664307580043,
    0.39073112848927377, 0.37460659341591224, 0.3583679495453002,
    0.3420201433256689, 0.3255681544571566, 0.3090169943749475,
    0.2923717047227366, 0.2756373558169992, 0.258819045102521,
    0.24192189559966773, 0.2249510543438652, 0.2079116908177593,
    0.19080899537654497, 0.17364817766693025, 0.15643446504023098,
    0.1391731009600653, 0.12186934340514755, 0.10452846326765373,
    0.0871557427476582, 0.06975647374412552, 0.05233595624294381,
    0.03489949670250114, 0.017452406437283435,
    0.0
};

/**
 * Ensure that a degree value is within [0..360).
 */
int deg_range(int val) {
    while (val < 0) {
        val += 360;
    }
    return val % 360;
}

// Retrieves value from the lookup table, after normalizing the degree
// value to be within [0..360).
float degsin(int deg) {
    deg = deg_range(deg);

    if (deg >= 0 && deg <= 180) {
        return sin_table[deg];
    }
    if (deg > 180 && deg < 360) {
        return -sin_table[deg - 180];
    }
}

// Precomputed float values that we'll pass to sin() for testing.
float vals[360];

int main(int argc, char *argv[]) {
    int a, b;
    clock_t start, diff;

    printf("Speed test for sin() versus a lookup table sin().\r\n");

    printf("Getting ready for sin() test...\r\n");
    // Precompute sin() values.
    for (int b = 0; b < 360; ++b) {
        vals[b] = b * (3.14159265359 / 180);
    }
    // Warming up...
    for (int a = 0; a < 10000; ++a) {
        for (int b = 0; b < 360; ++b) {
            sin(vals[b]);
        }
    }
    for (int a = 0; a < 10000; ++a) {
        for (int b = 0; b < 360; ++b) {
            sin(vals[b]);
        }
    }
    // sin() test.
    start = clock();
    printf("Start sin() test...");
    for (int a = 0; a < 10000; ++a) {
        for (int b = 0; b < 360; ++b) {
            sin(vals[b]);
        }
    }
    printf(" done.\r\n");
    diff = clock() - start;
    printf("10,000 iterations of 360 degrees took %d msec with sin().\r\n", diff * 1000 / CLOCKS_PER_SEC);

    // Warming up for the lookup table test.
    for (int a = 0; a < 10000; ++a) {
        for (int b = 0; b < 360; ++b) {
            degsin(vals[b]);
        }
    }
    for (int a = 0; a < 10000; ++a) {
        for (int b = 0; b < 360; ++b) {
            degsin(vals[b]);
        }
    }
    // Lookup table test.
    start = clock();
    printf("Start degsin() test...");
    for (int a = 0; a < 10000; ++a) {
        for (int b = 0; b < 360; ++b) {
            degsin(b);
        }
    }
    printf(" done.\r\n");
    diff = clock() - start;
    printf("10,000 iterations of 360 degrees took %d msec with degsin().\r\n", diff * 1000 / CLOCKS_PER_SEC);

    return 0;
}

Result: