diff options
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> |