Benchmarks
Check original sparsepp repository and write-up which compares hashmap implementations.
Use sparsepp from another package
To use C++ code from sparsepp:
- In DESCRIPTION, add
LinkingTo: sparsepp. - 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';
}