Skip to content

Rcpp interface to sparsepp - efficient hash map for C++

License

Notifications You must be signed in to change notification settings

dselivanov/r-sparsepp

Folders and files

NameName
Last commit message
Last commit date
Mar 5, 2018
Sep 22, 2018
Mar 5, 2018
Sep 22, 2018
Dec 30, 2016
Sep 22, 2018
Sep 22, 2018
Dec 30, 2016
Dec 29, 2016
Sep 22, 2018
Aug 7, 2017
Aug 7, 2017
Dec 29, 2016
Sep 22, 2018

Repository files navigation

CRAN_Status_Badge License

Benchmarks

Check original sparsepp repository and write-up which compares hashmap implementations.

insert-benchmark

Use sparsepp from another package

To use C++ code from sparsepp:

  1. In DESCRIPTION, add LinkingTo: sparsepp.
  2. In the C++ file, add: #include <sparsepp/spp.h>

Simple example

#include <sparsepp/spp.h>
using spp::sparse_hash_map;
sparse_hash_map<string, int> smap;

Defining custom hash function

#include <iostream>
#include <functional>
#include <string>
#include <sparsepp/spp.h>

using std::string;

struct Person 
{
    bool operator==(const Person &o) const 
    { return _first == o._first && _last == o._last; }

    string _first;
    string _last;
};

namespace std
{
    // inject specialization of std::hash for Person into namespace std
    // ----------------------------------------------------------------
    template<> 
    struct hash<Person>
    {
        std::size_t operator()(Person const &p) const
        {
            std::size_t seed = 0;
            spp::hash_combine(seed, p._first);
            spp::hash_combine(seed, p._last);
            return seed;
        }
    };
}

int main()
{
    // As we have defined a specialization of std::hash() for Person, 
    // we can now create sparse_hash_set or sparse_hash_map of Persons
    // ----------------------------------------------------------------
    spp::sparse_hash_set<Person> persons = { { "John", "Galt" }, 
                                             { "Jane", "Doe" } };
    for (auto& p: persons)
        std::cout << p._first << ' ' << p._last << '\n';
}