mapのイテレーション速度を測定

test-map-iteration.cc

#include <map>
#include <random>
#include <iostream>
#include <cmath>
#include <sys/time.h>

using namespace std;

double mytime() {
    timeval tv;
    gettimeofday(&tv, NULL);
    return tv.tv_sec + tv.tv_usec * 0.000001;
}

int main() {
    random_device r;
    for (int i = 0; i < 2000; ++i) {
        map<int,int> m;
        int jmax = (int)pow(1.01, i);
        for (int j = 0; j < jmax; ++j) {
            int k = r();
            while (m.find(k) != m.end()) k = r();
            m[k] = j;
        }
        volatile int sum = 0;
        double begin = mytime();
        for (auto kv : m) ++sum;
        double e = mytime() - begin;
        cout << i << ' ' << sum << ' ' << e << ' ' << e/(double)sum << ' ' << endl;
    }
}