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Diffstat (limited to 'libstdc++-v3/doc/xml/manual/parallel_mode.xml')
| -rw-r--r-- | libstdc++-v3/doc/xml/manual/parallel_mode.xml | 79 |
1 files changed, 67 insertions, 12 deletions
diff --git a/libstdc++-v3/doc/xml/manual/parallel_mode.xml b/libstdc++-v3/doc/xml/manual/parallel_mode.xml index faea5a9e7f6..7cb2a05986f 100644 --- a/libstdc++-v3/doc/xml/manual/parallel_mode.xml +++ b/libstdc++-v3/doc/xml/manual/parallel_mode.xml @@ -105,18 +105,45 @@ It might work with other compilers, though.</para> <sect1 id="manual.ext.parallel_mode.using" xreflabel="Using"> <title>Using</title> +<sect2 id="parallel_mode.using.prereq_flags" xreflabel="using.prereq_flags"> + <title>Prerequisite Compiler Flags</title> + +<para> + 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 <literal>-fopenmp</literal>. This will link + in <code>libgomp</code>, the GNU + OpenMP <ulink url="http://gcc.gnu.org/onlinedocs/libgomp/">implementation</ulink>, + whose presence is mandatory. +</para> + +<para> +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 <literal>-march=i686</literal>, + <literal>-march=native</literal> or <literal>-mcpu=v9</literal>. See + the GCC manual for more information. +</para> + +</sect2> + <sect2 id="parallel_mode.using.parallel_mode" xreflabel="using.parallel_mode"> <title>Using Parallel Mode</title> <para> To use the libstdc++ parallel mode, compile your application with - the compiler flag <constant>-D_GLIBCXX_PARALLEL -fopenmp</constant>. This - will link in <code>libgomp</code>, the GNU OpenMP <ulink url="http://gcc.gnu.org/onlinedocs/libgomp/">implementation</ulink>, - whose presence is mandatory. In addition, hardware capable of atomic - operations is mandatory. Actually activating these atomic - operations may require explicit compiler flags on some targets - (like sparc and x86), such as <literal>-march=i686</literal>, - <literal>-march=native</literal> or <literal>-mcpu=v9</literal>. + the prerequisite flags as detailed above, and in addition + add <constant>-D_GLIBCXX_PARALLEL</constant>. 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. </para> <para>Note that the <constant>_GLIBCXX_PARALLEL</constant> define may change the @@ -129,7 +156,7 @@ It might work with other compilers, though.</para> </para> </sect2> -<sect2 id="manual.ext.parallel_mode.usings" xreflabel="using.specific"> +<sect2 id="parallel_mode.using.specific" xreflabel="using.specific"> <title>Using Specific Parallel Components</title> <para>When it is not feasible to recompile your entire application, or @@ -138,9 +165,38 @@ It might work with other compilers, though.</para> 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. The - following table provides the names and headers of the parallel - algorithms: + compiled with either release mode or with parallel mode. +</para> + + +<para>An example of using a parallel version +of <function>std::sort</function>, but no other parallel algorithms, is: +</para> + +<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; +} +</programlisting> + +<para> +Then compile this code with the prerequisite compiler flags +(<literal>-fopenmp</literal> and any necessary architecture-specific +flags for atomic operations.) +</para> + +<para> The following table provides the names and headers of all the + parallel algorithms that can be used in a similar manner: </para> <table frame='all'> @@ -416,7 +472,6 @@ It might work with other compilers, though.</para> <sect2 id="manual.ext.parallel_mode.design.intro" xreflabel="Intro"> <title>Interface Basics</title> - <para> All parallel algorithms are intended to have signatures that are equivalent to the ISO C++ algorithms replaced. For instance, the |