TestSignbit.cpp

#include <algorithm>
#include <random>
#include <vector>

using namespace std;
using namespace std::chrono;

int main() {

    // First create an instance of an engine.
    random_device rnd_device;
    // Specify the engine and distribution.
    mt19937 mersenne_engine{rnd_device()};  // Generates random integers
    uniform_int_distribution<int> dist{1, 10000};

    auto gen = [&dist, &mersenne_engine]() {
        return static_cast<float>(dist(mersenne_engine)) / 10000;
    };

    int numElements = 100000000;

    vector<float> v1(numElements);
    vector<float> v2(numElements);

    generate(begin(v1), end(v1), gen);
    generate(begin(v2), end(v2), gen);

    vector<float> v3;
    int i(0);
    while (i < numElements) {
        v3.emplace_back(v1[i] - v2[i]);
        ++i;
    }

    i = 0;
    int dummy(0);

    //// Uncomment/comment for IF/ELSE comparison ////
//    while (i < numElements) {
//        if (v3[i] >= 0) {
//            ++dummy;
//        } else {
//            --dummy;
//        }
//        ++i;
//    }

    //// Uncomment/comment for std::signbit comparison ////
    while (i < numElements) {
        if (std::signbit(v3[i])) {
            ++dummy;
        } else {
            --dummy;
        }
        ++i;
    }

    return 0;
}