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diff --git a/libstdc++-v3/docs/html/parallel_mode.html b/libstdc++-v3/docs/html/parallel_mode.html index 74db8ca..5843ae8 100644 --- a/libstdc++-v3/docs/html/parallel_mode.html +++ b/libstdc++-v3/docs/html/parallel_mode.html @@ -388,26 +388,109 @@ computing.</p> <p> Something about compile-time settings and configuration, ie using <code>__gnu_parallel::Settings</code>. XXX Up in the air.</p> -<h4 class="left">Interface basics and relevant namespaces</h4> +<h4 class="left">Interface basics and general design</h4> + +<p>All parallel algorithms are intended to have signatures that are +equivalent to the ISO C++ algorithms replaced. For instance, the +<code>std::adjacent_find</code> function is declared as: + +<pre> +namespace std +{ + template<typename _FIter> + _FIter + adjacent_find(_FIter, _FIter); +} +</pre> + +Which means that there should be something equivalent for the parallel +version. Indeed, this is the case: + +<pre> +namespace std +{ + namespace __parallel + { + template<typename _FIter> + _FIter + adjacent_find(_FIter, _FIter); + + ... + } +} +</pre> + +<p>But.... why the elipses? +</p> -<p> Two namespaces contain the parallel mode: -<code>std::__parallel</code> and <code>__gnu_parallel</code>. +<p> The elipses 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> Compile-time conditions are referred to as "embarrassingly +parallel," and are denoted with the appropriate dispatch object, ie +one of <code>__gnu_parallel::sequential_tag</code>, +<code>__gnu_parallel::parallel_tag</code>, +<code>__gnu_parallel::balanced_tag</code>, +<code>__gnu_parallel::unbalanced_tag</code>, +<code>__gnu_parallel::omp_loop_tag</code>, or +<code>__gnu_parallel::omp_loop_static_tag</code>. </p> +<p> Run-time conditions depend on the hardware being used, the number +of threads available, etc., and are denoted by the use of the enum +<code>__gnu_parallel::parallelism</code>. Values of this enum include +<code>__gnu_parallel::sequential</code>, +<code>__gnu_parallel::parallel_unbalanced</code>, +<code>__gnu_parallel::parallel_balanced</code>, +<code>__gnu_parallel::parallel_omp_loop</code>, +<code>__gnu_parallel::parallel_omp_loop_static</code>, or +<code>__gnu_parallel::parallel_taskqueue</code>. +</p> + +<p> Putting all this together, the general view of overloads for the +parallel algorithms look like this: +<p> +<ul> + <li>ISO C++ signature</li> + <li>ISO C++ signature + sequential_tag argument</li> + <li>ISO C++ signature + parallelism argument</li> +</ul> + +<p> Please note that the implementation may use additional functions +(designated with the <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> + + +<h4 class="left">Relevant namespaces</h4> + <p> One namespace contain versions of code that are explicitly sequential: <code>__gnu_serial</code>. </p> -<p> Parallel implementations of the sequential standard components are -defined in <code>namespace std::__parallel</code>. For instance, -<code>std::transform</code> from <algorithm> has a parallel -counterpart in <code>std::__parallel::transform</code> from +<p> Two namespaces contain the parallel mode: +<code>std::__parallel</code> and <code>__gnu_parallel</code>. +</p> + +<p> Parallel implementations of standard components, including +template helpers to select parallelism, are defined in <code>namespace +std::__parallel</code>. For instance, <code>std::transform</code> from +<algorithm> has a parallel counterpart in +<code>std::__parallel::transform</code> from <parallel/algorithm>. In addition, these parallel implementatations are injected into <code>namespace -__gnu_parallel</code> with using declarations. +__gnu_parallel</code> with using declarations. </p> -<p> Support and infrastructure is in <code>namespace __gnu_parallel</code>. +<p> Support and general infrastructure is in <code>namespace +__gnu_parallel</code>. </p> <p> More information, and an organized index of types and functions |