344 lines
12 KiB
C++
344 lines
12 KiB
C++
// -*- C++ -*-
|
|
|
|
// Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
|
|
//
|
|
// This file is part of the GNU ISO C++ Library. This library is free
|
|
// software; you can redistribute it and/or modify it under the terms
|
|
// of the GNU General Public License as published by the Free Software
|
|
// Foundation; either version 3, or (at your option) any later
|
|
// version.
|
|
|
|
// This library is distributed in the hope that it will be useful, but
|
|
// WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
// General Public License for more details.
|
|
|
|
// Under Section 7 of GPL version 3, you are granted additional
|
|
// permissions described in the GCC Runtime Library Exception, version
|
|
// 3.1, as published by the Free Software Foundation.
|
|
|
|
// You should have received a copy of the GNU General Public License and
|
|
// a copy of the GCC Runtime Library Exception along with this program;
|
|
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
|
|
// <http://www.gnu.org/licenses/>.
|
|
|
|
/** @file parallel/settings.h
|
|
* @brief Runtime settings and tuning parameters, heuristics to decide
|
|
* whether to use parallelized algorithms.
|
|
* This file is a GNU parallel extension to the Standard C++ Library.
|
|
*
|
|
* @section parallelization_decision
|
|
* The decision whether to run an algorithm in parallel.
|
|
*
|
|
* There are several ways the user can switch on and __off the parallel
|
|
* execution of an algorithm, both at compile- and run-time.
|
|
*
|
|
* Only sequential execution can be forced at compile-time. This
|
|
* reduces code size and protects code parts that have
|
|
* non-thread-safe side effects.
|
|
*
|
|
* Ultimately, forcing parallel execution at compile-time makes
|
|
* sense. Often, the sequential algorithm implementation is used as
|
|
* a subroutine, so no reduction in code size can be achieved. Also,
|
|
* the machine the program is run on might have only one processor
|
|
* core, so to avoid overhead, the algorithm is executed
|
|
* sequentially.
|
|
*
|
|
* To force sequential execution of an algorithm ultimately at
|
|
* compile-time, the user must add the tag
|
|
* gnu_parallel::sequential_tag() to the end of the parameter list,
|
|
* e. g.
|
|
*
|
|
* \code
|
|
* std::sort(__v.begin(), __v.end(), __gnu_parallel::sequential_tag());
|
|
* \endcode
|
|
*
|
|
* This is compatible with all overloaded algorithm variants. No
|
|
* additional code will be instantiated, at all. The same holds for
|
|
* most algorithm calls with iterators not providing random access.
|
|
*
|
|
* If the algorithm call is not forced to be executed sequentially
|
|
* at compile-time, the decision is made at run-time.
|
|
* The global variable __gnu_parallel::_Settings::algorithm_strategy
|
|
* is checked. _It is a tristate variable corresponding to:
|
|
*
|
|
* a. force_sequential, meaning the sequential algorithm is executed.
|
|
* b. force_parallel, meaning the parallel algorithm is executed.
|
|
* c. heuristic
|
|
*
|
|
* For heuristic, the parallel algorithm implementation is called
|
|
* only if the input size is sufficiently large. For most
|
|
* algorithms, the input size is the (combined) length of the input
|
|
* sequence(__s). The threshold can be set by the user, individually
|
|
* for each algorithm. The according variables are called
|
|
* gnu_parallel::_Settings::[algorithm]_minimal_n .
|
|
*
|
|
* For some of the algorithms, there are even more tuning options,
|
|
* e. g. the ability to choose from multiple algorithm variants. See
|
|
* below for details.
|
|
*/
|
|
|
|
// Written by Johannes Singler and Felix Putze.
|
|
|
|
#ifndef _GLIBCXX_PARALLEL_SETTINGS_H
|
|
#define _GLIBCXX_PARALLEL_SETTINGS_H 1
|
|
|
|
#include <parallel/types.h>
|
|
|
|
/**
|
|
* @brief Determine at compile(?)-time if the parallel variant of an
|
|
* algorithm should be called.
|
|
* @param __c A condition that is convertible to bool that is overruled by
|
|
* __gnu_parallel::_Settings::algorithm_strategy. Usually a decision
|
|
* based on the input size.
|
|
*/
|
|
#define _GLIBCXX_PARALLEL_CONDITION(__c) \
|
|
(__gnu_parallel::_Settings::get().algorithm_strategy \
|
|
!= __gnu_parallel::force_sequential \
|
|
&& ((__gnu_parallel::__get_max_threads() > 1 && (__c)) \
|
|
|| __gnu_parallel::_Settings::get().algorithm_strategy \
|
|
== __gnu_parallel::force_parallel))
|
|
|
|
/*
|
|
inline bool
|
|
parallel_condition(bool __c)
|
|
{
|
|
bool ret = false;
|
|
const _Settings& __s = _Settings::get();
|
|
if (__s.algorithm_strategy != force_seqential)
|
|
{
|
|
if (__s.algorithm_strategy == force_parallel)
|
|
ret = true;
|
|
else
|
|
ret = __get_max_threads() > 1 && __c;
|
|
}
|
|
return ret;
|
|
}
|
|
*/
|
|
|
|
namespace __gnu_parallel
|
|
{
|
|
/// class _Settings
|
|
/// Run-time settings for the parallel mode including all tunable parameters.
|
|
struct _Settings
|
|
{
|
|
_AlgorithmStrategy algorithm_strategy;
|
|
|
|
_SortAlgorithm sort_algorithm;
|
|
_PartialSumAlgorithm partial_sum_algorithm;
|
|
_MultiwayMergeAlgorithm multiway_merge_algorithm;
|
|
_FindAlgorithm find_algorithm;
|
|
|
|
_SplittingAlgorithm sort_splitting;
|
|
_SplittingAlgorithm merge_splitting;
|
|
_SplittingAlgorithm multiway_merge_splitting;
|
|
|
|
// Per-algorithm settings.
|
|
|
|
/// Minimal input size for accumulate.
|
|
_SequenceIndex accumulate_minimal_n;
|
|
|
|
/// Minimal input size for adjacent_difference.
|
|
unsigned int adjacent_difference_minimal_n;
|
|
|
|
/// Minimal input size for count and count_if.
|
|
_SequenceIndex count_minimal_n;
|
|
|
|
/// Minimal input size for fill.
|
|
_SequenceIndex fill_minimal_n;
|
|
|
|
/// Block size increase factor for find.
|
|
double find_increasing_factor;
|
|
|
|
/// Initial block size for find.
|
|
_SequenceIndex find_initial_block_size;
|
|
|
|
/// Maximal block size for find.
|
|
_SequenceIndex find_maximum_block_size;
|
|
|
|
/// Start with looking for this many elements sequentially, for find.
|
|
_SequenceIndex find_sequential_search_size;
|
|
|
|
/// Minimal input size for for_each.
|
|
_SequenceIndex for_each_minimal_n;
|
|
|
|
/// Minimal input size for generate.
|
|
_SequenceIndex generate_minimal_n;
|
|
|
|
/// Minimal input size for max_element.
|
|
_SequenceIndex max_element_minimal_n;
|
|
|
|
/// Minimal input size for merge.
|
|
_SequenceIndex merge_minimal_n;
|
|
|
|
/// Oversampling factor for merge.
|
|
unsigned int merge_oversampling;
|
|
|
|
/// Minimal input size for min_element.
|
|
_SequenceIndex min_element_minimal_n;
|
|
|
|
/// Minimal input size for multiway_merge.
|
|
_SequenceIndex multiway_merge_minimal_n;
|
|
|
|
/// Oversampling factor for multiway_merge.
|
|
int multiway_merge_minimal_k;
|
|
|
|
/// Oversampling factor for multiway_merge.
|
|
unsigned int multiway_merge_oversampling;
|
|
|
|
/// Minimal input size for nth_element.
|
|
_SequenceIndex nth_element_minimal_n;
|
|
|
|
/// Chunk size for partition.
|
|
_SequenceIndex partition_chunk_size;
|
|
|
|
/// Chunk size for partition, relative to input size. If > 0.0,
|
|
/// this value overrides partition_chunk_size.
|
|
double partition_chunk_share;
|
|
|
|
/// Minimal input size for partition.
|
|
_SequenceIndex partition_minimal_n;
|
|
|
|
/// Minimal input size for partial_sort.
|
|
_SequenceIndex partial_sort_minimal_n;
|
|
|
|
/// Ratio for partial_sum. Assume "sum and write result" to be
|
|
/// this factor slower than just "sum".
|
|
float partial_sum_dilation;
|
|
|
|
/// Minimal input size for partial_sum.
|
|
unsigned int partial_sum_minimal_n;
|
|
|
|
/// Minimal input size for random_shuffle.
|
|
unsigned int random_shuffle_minimal_n;
|
|
|
|
/// Minimal input size for replace and replace_if.
|
|
_SequenceIndex replace_minimal_n;
|
|
|
|
/// Minimal input size for set_difference.
|
|
_SequenceIndex set_difference_minimal_n;
|
|
|
|
/// Minimal input size for set_intersection.
|
|
_SequenceIndex set_intersection_minimal_n;
|
|
|
|
/// Minimal input size for set_symmetric_difference.
|
|
_SequenceIndex set_symmetric_difference_minimal_n;
|
|
|
|
/// Minimal input size for set_union.
|
|
_SequenceIndex set_union_minimal_n;
|
|
|
|
/// Minimal input size for parallel sorting.
|
|
_SequenceIndex sort_minimal_n;
|
|
|
|
/// Oversampling factor for parallel std::sort (MWMS).
|
|
unsigned int sort_mwms_oversampling;
|
|
|
|
/// Such many samples to take to find a good pivot (quicksort).
|
|
unsigned int sort_qs_num_samples_preset;
|
|
|
|
/// Maximal subsequence __length to switch to unbalanced __base case.
|
|
/// Applies to std::sort with dynamically load-balanced quicksort.
|
|
_SequenceIndex sort_qsb_base_case_maximal_n;
|
|
|
|
/// Minimal input size for parallel std::transform.
|
|
_SequenceIndex transform_minimal_n;
|
|
|
|
/// Minimal input size for unique_copy.
|
|
_SequenceIndex unique_copy_minimal_n;
|
|
|
|
_SequenceIndex workstealing_chunk_size;
|
|
|
|
// Hardware dependent tuning parameters.
|
|
|
|
/// size of the L1 cache in bytes (underestimation).
|
|
unsigned long long L1_cache_size;
|
|
|
|
/// size of the L2 cache in bytes (underestimation).
|
|
unsigned long long L2_cache_size;
|
|
|
|
/// size of the Translation Lookaside Buffer (underestimation).
|
|
unsigned int TLB_size;
|
|
|
|
/// Overestimation of cache line size. Used to avoid false
|
|
/// sharing, i.e. elements of different threads are at least this
|
|
/// amount apart.
|
|
unsigned int cache_line_size;
|
|
|
|
// Statistics.
|
|
|
|
/// The number of stolen ranges in load-balanced quicksort.
|
|
_SequenceIndex qsb_steals;
|
|
|
|
/// Minimal input size for search and search_n.
|
|
_SequenceIndex search_minimal_n;
|
|
|
|
/// Block size scale-down factor with respect to current position.
|
|
float find_scale_factor;
|
|
|
|
/// Get the global settings.
|
|
_GLIBCXX_CONST static const _Settings&
|
|
get() throw();
|
|
|
|
/// Set the global settings.
|
|
static void
|
|
set(_Settings&) throw();
|
|
|
|
explicit
|
|
_Settings() :
|
|
algorithm_strategy(heuristic),
|
|
sort_algorithm(MWMS),
|
|
partial_sum_algorithm(LINEAR),
|
|
multiway_merge_algorithm(LOSER_TREE),
|
|
find_algorithm(CONSTANT_SIZE_BLOCKS),
|
|
sort_splitting(EXACT),
|
|
merge_splitting(EXACT),
|
|
multiway_merge_splitting(EXACT),
|
|
accumulate_minimal_n(1000),
|
|
adjacent_difference_minimal_n(1000),
|
|
count_minimal_n(1000),
|
|
fill_minimal_n(1000),
|
|
find_increasing_factor(2.0),
|
|
find_initial_block_size(256),
|
|
find_maximum_block_size(8192),
|
|
find_sequential_search_size(256),
|
|
for_each_minimal_n(1000),
|
|
generate_minimal_n(1000),
|
|
max_element_minimal_n(1000),
|
|
merge_minimal_n(1000),
|
|
merge_oversampling(10),
|
|
min_element_minimal_n(1000),
|
|
multiway_merge_minimal_n(1000),
|
|
multiway_merge_minimal_k(2), multiway_merge_oversampling(10),
|
|
nth_element_minimal_n(1000),
|
|
partition_chunk_size(1000),
|
|
partition_chunk_share(0.0),
|
|
partition_minimal_n(1000),
|
|
partial_sort_minimal_n(1000),
|
|
partial_sum_dilation(1.0f),
|
|
partial_sum_minimal_n(1000),
|
|
random_shuffle_minimal_n(1000),
|
|
replace_minimal_n(1000),
|
|
set_difference_minimal_n(1000),
|
|
set_intersection_minimal_n(1000),
|
|
set_symmetric_difference_minimal_n(1000),
|
|
set_union_minimal_n(1000),
|
|
sort_minimal_n(1000),
|
|
sort_mwms_oversampling(10),
|
|
sort_qs_num_samples_preset(100),
|
|
sort_qsb_base_case_maximal_n(100),
|
|
transform_minimal_n(1000),
|
|
unique_copy_minimal_n(10000),
|
|
workstealing_chunk_size(100),
|
|
L1_cache_size(16 << 10),
|
|
L2_cache_size(256 << 10),
|
|
TLB_size(128),
|
|
cache_line_size(64),
|
|
qsb_steals(0),
|
|
search_minimal_n(1000),
|
|
find_scale_factor(0.01f)
|
|
{ }
|
|
};
|
|
}
|
|
|
|
#endif /* _GLIBCXX_PARALLEL_SETTINGS_H */
|