core/test/modules/RandomTests.cpp

module Tests;
import Core.Random;
import Core.Test;
import Core.Array;

using Core::Random;

static void testAverage(bool light) {
    int limit = light ? 100'000 : 1'000'000;
    Random r(553);
    float sum = 0;
    for(int i = 0; i < limit; i++) {
        sum += static_cast<float>(r.nextU32(2, 11));
    }
    sum /= static_cast<float>(limit);
    Core::testFloat(6.0f, sum, 0.01f);
}

static void testCoin(bool light) {
    int limit = light ? 100'000 : 1'000'000;
    Random r(5533);
    int c[2] = {0, 0};
    for(int i = 0; i < limit; i++) {
        c[r.nextBool()]++;
    }
    Core::testFloat(
        0.0f, static_cast<float>(c[0] - c[1]) / static_cast<float>(limit),
        0.003f);
}

static void testDistribution(bool light) {
    size_t limit = light ? 100'000 : 1'000'000;
    Random r(553);
    Core::Array<int, 102> c;
    for(size_t i = 0; i < limit; i++) {
        c[r.nextSize(1, c.getLength() - 1)]++;
    }
    Core::test(0, c[0]);
    Core::test(0, c[c.getLength() - 1]);
    for(size_t i = 1; i < c.getLength() - 1; i++) {
        Core::testFloat(
            0.01f, static_cast<float>(c[i]) / static_cast<float>(limit),
            0.001f);
    }
}

static void testFloatAverage(bool light) {
    int limit = light ? 100'000 : 1'000'000;
    Core::Random r(553);
    float sum = 0;
    for(int i = 0; i < limit; i++) {
        sum += r.nextFloat();
    }
    sum /= static_cast<float>(limit);
    Core::testFloat(0.5f, sum, 0.001f);
}

static void testFloatCoin(bool light) {
    int limit = light ? 100'000 : 1'000'000;
    Random r(5535);
    Core::Array<int, 2> c;
    for(int i = 0; i < limit; i++) {
        c[r.nextFloat() < 0.5f]++;
    }
    Core::testFloat(
        0.0f, static_cast<float>(c[0] - c[1]) / static_cast<float>(limit),
        0.003f);
}

static void testFloatDistribution(bool light) {
    int limit = light ? 100'000 : 1'000'000;
    Random r(553);
    Core::Array<int, 102> c;
    for(int i = 0; i < limit; i++) {
        c[static_cast<size_t>(1.0f + r.nextFloat() * (c.getLength() - 2))]++;
    }
    Core::test(0, c[0]);
    Core::test(0, c[c.getLength() - 1]);
    for(size_t i = 1; i < c.getLength() - 1; i++) {
        Core::testFloat(
            0.01f, static_cast<float>(c[i]) / static_cast<float>(limit),
            0.003f);
    }
}

static void testRandomI32() {
    Random r(56'346);
    Core::Array<int, 7> c;
    c.fill(0);
    for(int i = 0; i < 10'000; i++) {
        i32 index = r.nextI32(-2, 3) + 3;
        if(Core::testTrue(index >= 0)) {
            c[static_cast<size_t>(index)]++;
        }
    }
    for(size_t i = 0; i < c.getLength(); i++) {
        Core::test(i != 0 && i != c.getLength() - 1, c[i] > 0);
    }
}

void testRandom(bool light) {
    testAverage(light);
    testCoin(light);
    testDistribution(light);
    testFloatAverage(light);
    testFloatCoin(light);
    testFloatDistribution(light);
    testRandomI32();
}