Mixed Pool Creation and Algorithm Basics¶

This recipe shows how to create a default mixed pool, and one that might be tailored to a specific application’s needs. Mixed pools allocate in an array of umpire::strategy::FixedPool for small allocations, because these have simpler bookkeeping and are very fast, and a umpire::strategy::DynamicPool for larger allocations.

The class umpire::strategy::MixedPool uses a generic choice of umpire::strategy::FixedPool of size 256 bytes to 4MB in increments of powers of 2, while umpire::strategy::MixedPoolImpl has template arguments that select the first, power of 2 increment, and last fixed pool size.

The complete example is included below:

// Copyright (c) 2016-20, Lawrence Livermore National Security, LLC and Umpire
// project contributors. See the COPYRIGHT file for details.
// SPDX-License-Identifier: (MIT)
#include "umpire/strategy/MixedPool.hpp"

#include "umpire/Allocator.hpp"
#include "umpire/ResourceManager.hpp"

#include <iostream>

int main(int, char**) {
  auto& rm = umpire::ResourceManager::getInstance();
  auto allocator = rm.getAllocator("HOST");

   * Create a default mixed pool.
  auto default_mixed_allocator = rm.makeAllocator<umpire::strategy::MixedPool>(
    "default_mixed_pool", allocator);


   * Create a mixed pool using fixed pool bins of size 2^8 = 256 Bytes
   * to 2^14 = 16 kB in increments of 5x, where each individual fixed
   * pool is kept under 4MB in size to begin.
  auto custom_mixed_allocator = rm.makeAllocator<umpire::strategy::MixedPool>(
    "custom_mixed_pool", allocator, 256, 16*1024, 4*1024*1024, 5);

   * Although this calls for only 4*4=16 bytes, this allocation will
   * come from the smallest fixed pool, thus ptr will actually be the
   * first address in a range of 256 bytes.
  void *ptr1 = custom_mixed_allocator.allocate(4 * sizeof(int));

   * This is too beyond the range of the fixed pools, and therefore is
   * allocated from a dynamic pool. The range of address space
   * reserved will be exactly what was requested by the allocate()
   * method.
  void *ptr2 = custom_mixed_allocator.allocate(1 << 18);

   * Clean up

  return 0;