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| author | Simon Marlow <marlowsd@gmail.com> | 2011-12-06 15:12:07 +0000 |
|---|---|---|
| committer | Simon Marlow <marlowsd@gmail.com> | 2011-12-06 16:00:27 +0000 |
| commit | 92e7d6c92fdd14de424524564376d3522f2a40cc (patch) | |
| tree | 5715d44012b452f5020ca14331a1fe50d5fd9600 /docs/users_guide/using.xml | |
| parent | 8b75acd3ca25165536f18976c8d80cb62ad613e4 (diff) | |
| download | haskell-92e7d6c92fdd14de424524564376d3522f2a40cc.tar.gz | |
Allow the number of capabilities to be increased at runtime (#3729)
At present the number of capabilities can only be *increased*, not
decreased. The latter presents a few more challenges!
Diffstat (limited to 'docs/users_guide/using.xml')
| -rw-r--r-- | docs/users_guide/using.xml | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/docs/users_guide/using.xml b/docs/users_guide/using.xml index 5bd6f11148..441ad5914b 100644 --- a/docs/users_guide/using.xml +++ b/docs/users_guide/using.xml @@ -2112,8 +2112,10 @@ f "2" = 2 <sect2 id="parallel-options"> <title>RTS options for SMP parallelism</title> - <para>To run a program on multiple CPUs, use the - RTS <option>-N</option> option:</para> + <para>There are two ways to run a program on multiple + processors: + call <literal>GHC.Conc.setNumCapabilities</literal> from your + program, or use the RTS <option>-N</option> option.</para> <variablelist> <varlistentry> @@ -2148,7 +2150,13 @@ f "2" = 2 <para>The current value of the <option>-N</option> option is available to the Haskell program - via <literal>GHC.Conc.numCapabilities</literal>.</para> + via <literal>GHC.Conc.getNumCapabilities</literal>, and + it may be changed while the program is running by + calling <literal>GHC.Conc.setNumCapabilities</literal>. + Note: in the current implementation, + the <option>-N</option> value may only + be <emphasis>increased</emphasis>, not decreased, by + calling <literal>GHC.Conc.setNumCapabilities</literal>.</para> </listitem> </varlistentry> </variablelist> |