cli/DefaultsConfigurator.hpp

/**
 *   Copyright 2016, Quickstep Research Group, Computer Sciences Department,
 *     University of Wisconsin—Madison.
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 **/

#ifndef QUICKSTEP_CLI_DEFAULTS_CONFIGURATOR_HPP_
#define QUICKSTEP_CLI_DEFAULTS_CONFIGURATOR_HPP_

#include <thread>  // NOLINT(build/c++11)
#include <unordered_map>
#include <vector>

#include "utility/Macros.hpp"

#ifdef QUICKSTEP_HAVE_LIBNUMA
#include <numa.h>
#endif

namespace quickstep {

/** \addtogroup CLI
 * @{
 **/

/**
 * @brief A static class for setting the default configuration parameters in
 *        Quickstep.
 **/
class DefaultsConfigurator {
 public:
  /**
   * @brief Get the number of concurrent threads supported by the hardware,
   *
   * @note This function will return 0, if it fails (which it may on some
   *       machines/environments).
   **/
  static std::size_t GetNumHardwareThreads() {
    return std::thread::hardware_concurrency();
  }

  /**
   * @brief Get the number of NUMA nodes covered by the given worker affinities
   *        to the CPU cores.
   *
   * @param worker_cpu_affinities A vector V where V[i] is the CPU core to which
   *        worker with index i is affinitized.
   *
   * @return The number of NUMA nodes that are covered by the given set of
   *         workers.
   **/
  static std::size_t GetNumNUMANodesCoveredByWorkers(const std::vector<int> &worker_cpu_affinities) {
    if (!worker_cpu_affinities.empty()) {
     #ifdef QUICKSTEP_HAVE_LIBNUMA
      // Key = NUMA node, value = whether there is at least one worker whose
      // affinity is set to a core on the given NUMA node.
      std::unordered_map<int, bool> any_worker_on_numa_node;
      for (const int curr_cpu_core_id : worker_cpu_affinities) {
        const int curr_numa_node_id = numa_node_of_cpu(curr_cpu_core_id);
        if (curr_numa_node_id >= 0) {
          // Note - For the purpose of this function, the value is always true.
          // Therefore, we can rely on the size of the map to get the count.
          any_worker_on_numa_node[curr_numa_node_id] = true;
        }
      }
      return any_worker_on_numa_node.size();
     #endif
    }
    // When libnuma is not available, or worker affinities are not specified,
    // the default return value is 1.
    return 1;
  }

 private:
  /**
   * @brief Private constructor to disable instantiation of the class.
   **/
  DefaultsConfigurator();

  DISALLOW_COPY_AND_ASSIGN(DefaultsConfigurator);
};
/** @} */

}  // namespace quickstep

#endif  // QUICKSTEP_CLI_DEFAULTS_CONFIGURATOR_HPP_