realocation of <long, double> map takes very long after about 60mil updates about sparsepp HOT 6 CLOSED

vagrant@vagrant-ubuntu-trusty-64:/vagrant/tmp$ g++ -O2 -I.. keys.cc -o keys
vagrant@vagrant-ubuntu-trusty-64:/vagrant/tmp$ ./keys
els:          0, map_size:          0, num_present:          0 at Sun Jan  1 00:01:33 2017
els:   10000000, map_size:    6849514, num_present:    3150486 at Sun Jan  1 00:01:37 2017
els:   20000000, map_size:   10353403, num_present:    6496111 at Sun Jan  1 00:01:42 2017
els:   30000000, map_size:   15231352, num_present:    5122051 at Sun Jan  1 00:01:46 2017
els:   40000000, map_size:   22352845, num_present:    2878507 at Sun Jan  1 00:01:53 2017
els:   50000000, map_size:   28546365, num_present:    3806480 at Sun Jan  1 00:01:58 2017
els:   60000000, map_size:   33967341, num_present:    4579024 at Sun Jan  1 00:02:06 2017
els:   70000000, map_size:   40369410, num_present:    3597931 at Sun Jan  1 00:02:10 2017
els:   80000000, map_size:   46740765, num_present:    3628645 at Sun Jan  1 00:02:15 2017
els:   90000000, map_size:   53220303, num_present:    3520462 at Sun Jan  1 00:02:21 2017
els:  100000000, map_size:   60228564, num_present:    2991739 at Sun Jan  1 00:02:26 2017
els:  110000000, map_size:   64684927, num_present:    5543637 at Sun Jan  1 00:02:31 2017
els:  120000000, map_size:   71014663, num_present:    3670264 at Sun Jan  1 00:02:43 2017
els:  130000000, map_size:   77742400, num_present:    3272263 at Sun Jan  1 00:02:48 2017
els:  140000000, map_size:   83478135, num_present:    4264265 at Sun Jan  1 00:02:53 2017
els:  150000000, map_size:   90135208, num_present:    3342927 at Sun Jan  1 00:02:59 2017
els:  160000000, map_size:   96354061, num_present:    3781147 at Sun Jan  1 00:03:04 2017
els:  170000000, map_size:  102911284, num_present:    3442777 at Sun Jan  1 00:03:10 2017
els:  180000000, map_size:  109286371, num_present:    3624913 at Sun Jan  1 00:03:15 2017
els:  190000000, map_size:  115816683, num_present:    3469688 at Sun Jan  1 00:03:21 2017
els:  200000000, map_size:  121958054, num_present:    3858629 at Sun Jan  1 00:03:27 2017
els:  210000000, map_size:  128693156, num_present:    3264898 at Sun Jan  1 00:03:33 2017
els:  220000000, map_size:  135951840, num_present:    2741316 at Sun Jan  1 00:03:53 2017
els:  230000000, map_size:  141173034, num_present:    4778806 at Sun Jan  1 00:03:58 2017
els:  240000000, map_size:  147978238, num_present:    3194796 at Sun Jan  1 00:04:03 2017

#include <fstream>
#include <iostream>
#include <ctime>
#include <cstdio>
#include <sparsepp.h>

struct Hasher {
    size_t operator()(uint64_t a) const { return a * 1099511628211ULL; }
};

int main() 
{
    std::ifstream f("./keys.tmp", std::ios::binary);
    spp::sparse_hash_map<uint64_t, double, Hasher> map;

    long i = 0, num_present=0;

    while(!f.eof()) 
    {
        time_t ctt = time(0);
        if (i % 10000000ll == 0)
        {
            printf("els: %10lu, map_size: %10lu, num_present: %10lu at %s", 
                   i, map.size(), num_present, asctime(localtime(&ctt)));
            num_present=0;
        }
        uint64_t key;
        f.read((char*)&key, sizeof(key));
        if (map.find(key) != map.end())
            num_present++;

        map[key] += 1.0;
        i++;
    }
    return 0;
}