libgomp.texi (GOMP_CPU_AFFINITY): Updated.

2007-04-19  Daniel Franke  <franke.daniel@gmail.com>

        * libgomp.texi (GOMP_CPU_AFFINITY): Updated.

From-SVN: r123976

1 files changed, 19 insertions, 8 deletions

diff --git a/libgomp/libgomp.texi b/libgomp/libgomp.texi
index c48cf93..f92a5da 100644
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -895,14 +895,25 @@ dynamic scheduling and a chunk size of 1 is used.
 @cindex Environment Variable
 @table @asis
 @item @emph{Description}:
-A patch for this extension has been submitted, but was not yet applied at the
-time of writing.
-
-@item @emph{Reference}: 
-@uref{http://gcc.gnu.org/ml/gcc-patches/2006-05/msg00982.html, 
-GCC Patches Mailinglist}
-@uref{http://gcc.gnu.org/ml/gcc-patches/2006-05/msg01133.html,
-GCC Patches Mailinglist}
+Binds threads to specific CPUs. The variable should contain a space- or
+comma-separated list of CPUs. This list may contain different kind of 
+entries: either single CPU numbers in any order, a range of CPUs (M-N) 
+or a range with some stride (M-N:S). CPU numbers are zero based. For example,
+@code{GOMP_CPU_AFFINITY="0 3 1-2 4-15:2"} will bind the initial thread
+to CPU 0, the second to CPU 3, the third to CPU 1, the fourth to 
+CPU 2, the fifth to CPU 4, the sixth through tenth to CPUs 6, 8, 10, 12,
+and 14 respectively and then start assigning back from the beginning of
+the list. @code{GOMP_CPU_AFFINITY=0} binds all threads to CPU 0.
+
+There is no GNU OpenMP library routine to determine whether a CPU affinity 
+specification is in effect. As a workaround, language-specific library 
+functions, e.g., @code{getenv} in C or @code{GET_ENVIRONMENT_VARIABLE} in 
+Fortran, may be used to query the setting of the @code{GOMP_CPU_AFFINITY} 
+environment variable. A defined CPU affinity on startup cannot be changed 
+or disabled during the runtime of the application.
+
+If this environment variable is omitted, the host system will handle the 
+assignment of threads to CPUs. 
 @end table