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+<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Using</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.0" /><meta name="keywords" content=" C++ , library , parallel " /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="parallel_mode.html" title="Chapter 31. Parallel Mode" /><link rel="prev" href="bk01pt12ch31s02.html" title="Semantics" /><link rel="next" href="bk01pt12ch31s04.html" title="Design" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Using</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt12ch31s02.html">Prev</a> </td><th width="60%" align="center">Chapter 31. Parallel Mode</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch31s04.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.parallel_mode.using"></a>Using</h2></div></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="parallel_mode.using.prereq_flags"></a>Prerequisite Compiler Flags</h3></div></div></div><p>
+ Any use of parallel functionality requires additional compiler
+ and runtime support, in particular support for OpenMP. Adding this support is
+ not difficult: just compile your application with the compiler
+ flag <code class="literal">-fopenmp</code>. This will link
+ in <code class="code">libgomp</code>, the GNU
+ OpenMP <a class="ulink" href="http://gcc.gnu.org/onlinedocs/libgomp/" target="_top">implementation</a>,
+ whose presence is mandatory.
+</p><p>
+In addition, hardware that supports atomic operations and a compiler
+ capable of producing atomic operations is mandatory: GCC defaults to no
+ support for atomic operations on some common hardware
+ architectures. Activating atomic operations may require explicit
+ compiler flags on some targets (like sparc and x86), such
+ as <code class="literal">-march=i686</code>,
+ <code class="literal">-march=native</code> or <code class="literal">-mcpu=v9</code>. See
+ the GCC manual for more information.
+</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="parallel_mode.using.parallel_mode"></a>Using Parallel Mode</h3></div></div></div><p>
+ To use the libstdc++ parallel mode, compile your application with
+ the prerequisite flags as detailed above, and in addition
+ add <code class="constant">-D_GLIBCXX_PARALLEL</code>. This will convert all
+ use of the standard (sequential) algorithms to the appropriate parallel
+ equivalents. Please note that this doesn't necessarily mean that
+ everything will end up being executed in a parallel manner, but
+ rather that the heuristics and settings coded into the parallel
+ versions will be used to determine if all, some, or no algorithms
+ will be executed using parallel variants.
+</p><p>Note that the <code class="constant">_GLIBCXX_PARALLEL</code> define may change the
+ sizes and behavior of standard class templates such as
+ <code class="function">std::search</code>, and therefore one can only link code
+ compiled with parallel mode and code compiled without parallel mode
+ if no instantiation of a container is passed between the two
+ translation units. Parallel mode functionality has distinct linkage,
+ and cannot be confused with normal mode symbols.
+</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="parallel_mode.using.specific"></a>Using Specific Parallel Components</h3></div></div></div><p>When it is not feasible to recompile your entire application, or
+ only specific algorithms need to be parallel-aware, individual
+ parallel algorithms can be made available explicitly. These
+ parallel algorithms are functionally equivalent to the standard
+ drop-in algorithms used in parallel mode, but they are available in
+ a separate namespace as GNU extensions and may be used in programs
+ compiled with either release mode or with parallel mode.
+</p><p>An example of using a parallel version
+of <code class="function">std::sort</code>, but no other parallel algorithms, is:
+</p><pre class="programlisting">
+#include <vector>
+#include <parallel/algorithm>
+
+int main()
+{
+ std::vector<int> v(100);
+
+ // ...
+
+ // Explicitly force a call to parallel sort.
+ __gnu_parallel::sort(v.begin(), v.end());
+ return 0;
+}
+</pre><p>
+Then compile this code with the prerequisite compiler flags
+(<code class="literal">-fopenmp</code> and any necessary architecture-specific
+flags for atomic operations.)
+</p><p> The following table provides the names and headers of all the
+ parallel algorithms that can be used in a similar manner:
+</p><div class="table"><a id="id388611"></a><p class="title"><b>Table 31.1. Parallel Algorithms</b></p><div class="table-contents"><table summary="Parallel Algorithms" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left">Algorithm</th><th align="left">Header</th><th align="left">Parallel algorithm</th><th align="left">Parallel header</th></tr></thead><tbody><tr><td align="left"><code class="function">std::accumulate</code></td><td align="left"><code class="filename">numeric</code></td><td align="left"><code class="function">__gnu_parallel::accumulate</code></td><td align="left"><code class="filename">parallel/numeric</code></td></tr><tr><td align="left"><code class="function">std::adjacent_difference</code></td><td align="left"><code class="filename">numeric</code></td><td align="left"><code class="function">__gnu_parallel::adjacent_difference</code></td><td align="left"><code class="filename">parallel/numeric</code></td></tr><tr><td align="left"><code class="function">std::inner_product</code></td><td align="left"><code class="filename">numeric</code></td><td align="left"><code class="function">__gnu_parallel::inner_product</code></td><td align="left"><code class="filename">parallel/numeric</code></td></tr><tr><td align="left"><code class="function">std::partial_sum</code></td><td align="left"><code class="filename">numeric</code></td><td align="left"><code class="function">__gnu_parallel::partial_sum</code></td><td align="left"><code class="filename">parallel/numeric</code></td></tr><tr><td align="left"><code class="function">std::adjacent_find</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::adjacent_find</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::count</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::count</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::count_if</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::count_if</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::equal</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::equal</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::find</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::find</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::find_if</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::find_if</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::find_first_of</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::find_first_of</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::for_each</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::for_each</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::generate</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::generate</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::generate_n</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::generate_n</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::lexicographical_compare</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::lexicographical_compare</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::mismatch</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::mismatch</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::search</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::search</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::search_n</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::search_n</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::transform</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::transform</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::replace</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::replace</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::replace_if</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::replace_if</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::max_element</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::max_element</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::merge</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::merge</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::min_element</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::min_element</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::nth_element</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::nth_element</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::partial_sort</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::partial_sort</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::partition</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::partition</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::random_shuffle</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::random_shuffle</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::set_union</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::set_union</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::set_intersection</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::set_intersection</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::set_symmetric_difference</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::set_symmetric_difference</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::set_difference</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::set_difference</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::sort</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::sort</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::stable_sort</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::stable_sort</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr><tr><td align="left"><code class="function">std::unique_copy</code></td><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="function">__gnu_parallel::unique_copy</code></td><td align="left"><code class="filename">parallel/algorithm</code></td></tr></tbody></table></div></div><br class="table-break" /></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch31s02.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" 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