Sort Determinisim

sorttest.cpp

#include <assert.h>
#include <stdio.h>
#include <algorithm>
#include <random>
#include <vector>

using namespace std;

struct kv {
    unsigned int significant;
    unsigned int insignificant;
};

inline bool operator<(const kv& lhs, const kv& rhs) {
    return lhs.significant < rhs.significant;
}

int main() {
    vector<kv> values(1'000);
    for (size_t idx = 0; idx < 1'000; ++idx) {
        values[idx].significant = idx / 2;
        values[idx].insignificant = idx;
    }

    random_device rd;
    shuffle(values.begin(), values.end(), rd);
    vector<kv> valuesCopy = values;
    sort(values.begin(), values.end());
    sort(valuesCopy.begin(), valuesCopy.end());
    // if this assert can fail, sort is nondeterministic
    assert(memcmp(values.data(), valuesCopy.data(), 1'000 * sizeof(kv)) == 0);
}