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diff --git a/gcc-4.8.1/libstdc++-v3/doc/html/manual/parallel_mode_design.html b/gcc-4.8.1/libstdc++-v3/doc/html/manual/parallel_mode_design.html deleted file mode 100644 index 5c26d9046..000000000 --- a/gcc-4.8.1/libstdc++-v3/doc/html/manual/parallel_mode_design.html +++ /dev/null @@ -1,212 +0,0 @@ -<?xml version="1.0" encoding="UTF-8" standalone="no"?> -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Design</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.77.1" /><meta name="keywords" content="C++, library, parallel" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="parallel_mode.html" title="Chapter 18. Parallel Mode" /><link rel="prev" href="parallel_mode_using.html" title="Using" /><link rel="next" href="parallel_mode_test.html" title="Testing" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Design</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="parallel_mode_using.html">Prev</a> </td><th width="60%" align="center">Chapter 18. Parallel Mode</th><td width="20%" align="right"> <a accesskey="n" href="parallel_mode_test.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.parallel_mode.design"></a>Design</h2></div></div></div><p> - </p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="parallel_mode.design.intro"></a>Interface Basics</h3></div></div></div><p> -All parallel algorithms are intended to have signatures that are -equivalent to the ISO C++ algorithms replaced. For instance, the -<code class="function">std::adjacent_find</code> function is declared as: -</p><pre class="programlisting"> -namespace std -{ - template<typename _FIter> - _FIter - adjacent_find(_FIter, _FIter); -} -</pre><p> -Which means that there should be something equivalent for the parallel -version. Indeed, this is the case: -</p><pre class="programlisting"> -namespace std -{ - namespace __parallel - { - template<typename _FIter> - _FIter - adjacent_find(_FIter, _FIter); - - ... - } -} -</pre><p>But.... why the ellipses? -</p><p> The ellipses in the example above represent additional overloads -required for the parallel version of the function. These additional -overloads are used to dispatch calls from the ISO C++ function -signature to the appropriate parallel function (or sequential -function, if no parallel functions are deemed worthy), based on either -compile-time or run-time conditions. -</p><p> The available signature options are specific for the different -algorithms/algorithm classes.</p><p> The general view of overloads for the parallel algorithms look like this: -</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>ISO C++ signature</p></li><li class="listitem"><p>ISO C++ signature + sequential_tag argument</p></li><li class="listitem"><p>ISO C++ signature + algorithm-specific tag type - (several signatures)</p></li></ul></div><p> Please note that the implementation may use additional functions -(designated with the <code class="code">_switch</code> suffix) to dispatch from the -ISO C++ signature to the correct parallel version. Also, some of the -algorithms do not have support for run-time conditions, so the last -overload is therefore missing. -</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="parallel_mode.design.tuning"></a>Configuration and Tuning</h3></div></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="parallel_mode.design.tuning.omp"></a>Setting up the OpenMP Environment</h4></div></div></div><p> -Several aspects of the overall runtime environment can be manipulated -by standard OpenMP function calls. -</p><p> -To specify the number of threads to be used for the algorithms globally, -use the function <code class="function">omp_set_num_threads</code>. An example: -</p><pre class="programlisting"> -#include <stdlib.h> -#include <omp.h> - -int main() -{ - // Explicitly set number of threads. - const int threads_wanted = 20; - omp_set_dynamic(false); - omp_set_num_threads(threads_wanted); - - // Call parallel mode algorithms. - - return 0; -} -</pre><p> - Some algorithms allow the number of threads being set for a particular call, - by augmenting the algorithm variant. - See the next section for further information. -</p><p> -Other parts of the runtime environment able to be manipulated include -nested parallelism (<code class="function">omp_set_nested</code>), schedule kind -(<code class="function">omp_set_schedule</code>), and others. See the OpenMP -documentation for more information. -</p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="parallel_mode.design.tuning.compile"></a>Compile Time Switches</h4></div></div></div><p> -To force an algorithm to execute sequentially, even though parallelism -is switched on in general via the macro <code class="constant">_GLIBCXX_PARALLEL</code>, -add <code class="classname">__gnu_parallel::sequential_tag()</code> to the end -of the algorithm's argument list. -</p><p> -Like so: -</p><pre class="programlisting"> -std::sort(v.begin(), v.end(), __gnu_parallel::sequential_tag()); -</pre><p> -Some parallel algorithm variants can be excluded from compilation by -preprocessor defines. See the doxygen documentation on -<code class="code">compiletime_settings.h</code> and <code class="code">features.h</code> for details. -</p><p> -For some algorithms, the desired variant can be chosen at compile-time by -appending a tag object. The available options are specific to the particular -algorithm (class). -</p><p> -For the "embarrassingly parallel" algorithms, there is only one "tag object -type", the enum _Parallelism. -It takes one of the following values, -<code class="code">__gnu_parallel::parallel_tag</code>, -<code class="code">__gnu_parallel::balanced_tag</code>, -<code class="code">__gnu_parallel::unbalanced_tag</code>, -<code class="code">__gnu_parallel::omp_loop_tag</code>, -<code class="code">__gnu_parallel::omp_loop_static_tag</code>. -This means that the actual parallelization strategy is chosen at run-time. -(Choosing the variants at compile-time will come soon.) -</p><p> -For the following algorithms in general, we have -<code class="code">__gnu_parallel::parallel_tag</code> and -<code class="code">__gnu_parallel::default_parallel_tag</code>, in addition to -<code class="code">__gnu_parallel::sequential_tag</code>. -<code class="code">__gnu_parallel::default_parallel_tag</code> chooses the default -algorithm at compiletime, as does omitting the tag. -<code class="code">__gnu_parallel::parallel_tag</code> postpones the decision to runtime -(see next section). -For all tags, the number of threads desired for this call can optionally be -passed to the respective tag's constructor. -</p><p> -The <code class="code">multiway_merge</code> algorithm comes with the additional choices, -<code class="code">__gnu_parallel::exact_tag</code> and -<code class="code">__gnu_parallel::sampling_tag</code>. -Exact and sampling are the two available splitting strategies. -</p><p> -For the <code class="code">sort</code> and <code class="code">stable_sort</code> algorithms, there are -several additional choices, namely -<code class="code">__gnu_parallel::multiway_mergesort_tag</code>, -<code class="code">__gnu_parallel::multiway_mergesort_exact_tag</code>, -<code class="code">__gnu_parallel::multiway_mergesort_sampling_tag</code>, -<code class="code">__gnu_parallel::quicksort_tag</code>, and -<code class="code">__gnu_parallel::balanced_quicksort_tag</code>. -Multiway mergesort comes with the two splitting strategies for multi-way -merging. The quicksort options cannot be used for <code class="code">stable_sort</code>. -</p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="parallel_mode.design.tuning.settings"></a>Run Time Settings and Defaults</h4></div></div></div><p> -The default parallelization strategy, the choice of specific algorithm -strategy, the minimum threshold limits for individual parallel -algorithms, and aspects of the underlying hardware can be specified as -desired via manipulation -of <code class="classname">__gnu_parallel::_Settings</code> member data. -</p><p> -First off, the choice of parallelization strategy: serial, parallel, -or heuristically deduced. This corresponds -to <code class="code">__gnu_parallel::_Settings::algorithm_strategy</code> and is a -value of enum <span class="type">__gnu_parallel::_AlgorithmStrategy</span> -type. Choices -include: <span class="type">heuristic</span>, <span class="type">force_sequential</span>, -and <span class="type">force_parallel</span>. The default is <span class="type">heuristic</span>. -</p><p> -Next, the sub-choices for algorithm variant, if not fixed at compile-time. -Specific algorithms like <code class="function">find</code> or <code class="function">sort</code> -can be implemented in multiple ways: when this is the case, -a <code class="classname">__gnu_parallel::_Settings</code> member exists to -pick the default strategy. For -example, <code class="code">__gnu_parallel::_Settings::sort_algorithm</code> can -have any values of -enum <span class="type">__gnu_parallel::_SortAlgorithm</span>: <span class="type">MWMS</span>, <span class="type">QS</span>, -or <span class="type">QS_BALANCED</span>. -</p><p> -Likewise for setting the minimal threshold for algorithm -parallelization. Parallelism always incurs some overhead. Thus, it is -not helpful to parallelize operations on very small sets of -data. Because of this, measures are taken to avoid parallelizing below -a certain, pre-determined threshold. For each algorithm, a minimum -problem size is encoded as a variable in the -active <code class="classname">__gnu_parallel::_Settings</code> object. This -threshold variable follows the following naming scheme: -<code class="code">__gnu_parallel::_Settings::[algorithm]_minimal_n</code>. So, -for <code class="function">fill</code>, the threshold variable -is <code class="code">__gnu_parallel::_Settings::fill_minimal_n</code>, -</p><p> -Finally, hardware details like L1/L2 cache size can be hardwired -via <code class="code">__gnu_parallel::_Settings::L1_cache_size</code> and friends. -</p><p> -</p><p> -All these configuration variables can be changed by the user, if -desired. -There exists one global instance of the class <code class="classname">_Settings</code>, -i. e. it is a singleton. It can be read and written by calling -<code class="code">__gnu_parallel::_Settings::get</code> and -<code class="code">__gnu_parallel::_Settings::set</code>, respectively. -Please note that the first call return a const object, so direct manipulation -is forbidden. -See <a class="link" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a01005.html" target="_top"> - <code class="filename">settings.h</code></a> -for complete details. -</p><p> -A small example of tuning the default: -</p><pre class="programlisting"> -#include <parallel/algorithm> -#include <parallel/settings.h> - -int main() -{ - __gnu_parallel::_Settings s; - s.algorithm_strategy = __gnu_parallel::force_parallel; - __gnu_parallel::_Settings::set(s); - - // Do work... all algorithms will be parallelized, always. - - return 0; -} -</pre></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="parallel_mode.design.impl"></a>Implementation Namespaces</h3></div></div></div><p> One namespace contain versions of code that are always -explicitly sequential: -<code class="code">__gnu_serial</code>. -</p><p> Two namespaces contain the parallel mode: -<code class="code">std::__parallel</code> and <code class="code">__gnu_parallel</code>. -</p><p> Parallel implementations of standard components, including -template helpers to select parallelism, are defined in <code class="code">namespace -std::__parallel</code>. For instance, <code class="function">std::transform</code> from <code class="filename">algorithm</code> has a parallel counterpart in -<code class="function">std::__parallel::transform</code> from <code class="filename">parallel/algorithm</code>. In addition, these parallel -implementations are injected into <code class="code">namespace -__gnu_parallel</code> with using declarations. -</p><p> Support and general infrastructure is in <code class="code">namespace -__gnu_parallel</code>. -</p><p> More information, and an organized index of types and functions -related to the parallel mode on a per-namespace basis, can be found in -the generated source documentation. -</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="parallel_mode_using.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="parallel_mode.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="parallel_mode_test.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Using </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Testing</td></tr></table></div></body></html>
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