random kmers generation with phmap insertion

main.cpp

/*

simple random kmers generator with storage in parallel hash map.
clone: https://github.com/greg7mdp/parallel-hashmap.git

g++ -Ofast -O3 main.cpp

*/


#include "parallel-hashmap/parallel_hashmap/phmap.h"
#include <iostream>
#include <string>
#include <vector>
#include <random>
#include <cstdint>
#include <functional> //for std::function
#include <algorithm>  //for std::generate_n

using namespace std;

typedef std::vector<char> char_array;

char_array charset()
{
    //Change this to suit
    return char_array({'A','C','G','T'});
};    

std::string random_string(size_t length, std::function<char(void)> rand_char )
{
    std::string str(length,0);
    std::generate_n( str.begin(), length, rand_char );
    return str;
}


void dump(phmap::flat_hash_map<uint64_t, string> & kmers){
    for(auto kmer : kmers)
        cout << kmer.second << ": " << kmer.first << endl;
}



int main(){

    // Constanats
    const int kSize = 31;
    const int kmers_no = 1e6; // 1 million kmers
    const int loops = 10;


    // kmers parallel hashmap
    phmap::flat_hash_map<uint64_t, string> kmers;


    // Random kmers generator
    const auto ch_set = charset();
    std::default_random_engine rng(std::random_device{}());
    std::uniform_int_distribution<> dist(0, ch_set.size()-1);
    auto randchar = [ ch_set,&dist,&rng ](){return ch_set[ dist(rng) ];};  

    // hasher
    std::hash<std::string> kmer_hasher;

    
    for(int i = 0; i < loops; i++){
        
        // Insertion
        for(int j=0; j < kmers_no; j++){
            string kmer_str = random_string(kSize,randchar);
            uint64_t kmer_hash = kmer_hasher(kmer_str);
            kmers[kmer_hash] = kmer_str;
        }
        
        // kmers.clear();
    }

    // dump(kmers);
    // cout << "Inserted: " << kmers.size() << " kmers" << endl;


    return 0;
}