Metall  v0.28
A persistent memory allocator for data-centric analytics

This is an example of how to use a complex STL map container with Metall.

// Copyright 2019 Lawrence Livermore National Security, LLC and other Metall
// Project Developers. See the top-level COPYRIGHT file for details.
// SPDX-License-Identifier: (Apache-2.0 OR MIT)
#include <iostream>
#include <boost/container/scoped_allocator.hpp>
#include <boost/container/string.hpp>
#include <boost/container/map.hpp>
namespace bc = boost::container;
// Utility to generate a new allocator type for 'new_type'
template <typename allocator_type, typename new_type>
using rebind_alloc = typename std::allocator_traits<
allocator_type>::template rebind_alloc<new_type>;
// Key type
using key_type = int;
// Mapped type
template <typename _allocator_type>
struct mapped_type {
using allocator_type = _allocator_type;
bc::vector<int, rebind_alloc<_allocator_type, int>> vec;
bc::basic_string<char, std::char_traits<char>,
rebind_alloc<_allocator_type, char>>
explicit mapped_type(const allocator_type &allocator)
: vec(allocator), str(allocator) {}
// Value type
template <typename allocator_type>
using value_type = std::pair<const key_type, mapped_type<allocator_type>>;
// Map type
template <typename base_allocator_type>
using map_allocator_type = bc::scoped_allocator_adaptor<
rebind_alloc<base_allocator_type, value_type<base_allocator_type>>>;
template <typename base_allocator_type>
using map_type =
boost::container::map<key_type, mapped_type<base_allocator_type>,
std::less<>, map_allocator_type<base_allocator_type>>;
// Map type instantiated to Metall
using metall_map_type = map_type<metall::manager::allocator_type<std::byte>>;
int main() {
metall::manager manager(metall::create_only, "/tmp/datastore");
auto pmap =
pmap->at(0).str = "hello, world 0";
pmap->at(1).str = "hello, world 1";
metall::manager manager(metall::open_only, "/tmp/datastore");
auto pmap = manager.find<metall_map_type>("map").first;
std::cout << pmap->at(0).vec[0] << std::endl; // Prints out "0"
std::cout << pmap->at(0).str << std::endl; // Prints out "hello, world 0"
std::cout << pmap->at(1).vec[0] << std::endl; // Prints out "1"
std::cout << pmap->at(1).str << std::endl; // Prints out "hello, world 1"
return 0;
A generalized Metall manager class.
Definition: basic_manager.hpp:40
int main()
Definition: jgraph.cpp:24
boost::container::scoped_allocator_adaptor< OuterAlloc, InnerAlloc... > scoped_allocator_adaptor
An allocator which can be used with multilevel containers.
Definition: scoped_allocator.hpp:16
basic_manager<> manager
Default Metall manager class which is an alias of basic_manager with the default template parameters.
Definition: metall.hpp:34