Only add a barrier to 8 collectives. The other ones don't seem to need it

[simgrid.git] / docs / source / Configuring_SimGrid.rst

diff --git a/docs/source/Configuring_SimGrid.rst b/docs/source/Configuring_SimGrid.rst
index f5af4a0..6ed80fd 100644 (file)
--- a/docs/source/Configuring_SimGrid.rst
+++ b/docs/source/Configuring_SimGrid.rst
@@ -1376,13 +1376,13 @@ Add a barrier in all collectives
 
 **Option** ``smpi/barrier-collectives`` **default:** off
 
-This option adds a simple barrier in all collectives operation to catch dangerous
-code that may or may not work depending on the MPI implementation. It is disabled
-by default, and activated by the `-analyze` flag of smpirun.
+This option adds a simple barrier in some collective operations to catch dangerous
+code that may or may not work depending on the MPI implementation: Bcast, Exscan,
+Gather, Gatherv, Scan, Scatter, Scatterv and Reduce.
 
 For example, the following code works with OpenMPI while it deadlocks in MPICH and
-Intel MPI. It seems to mean that OpenMPI has a "fire and forget" implementation for
-Broadcast.
+Intel MPI. Broadcast seem to be "fire and forget" in OpenMPI while other
+implementations expect to receive a message.
 
 .. code-block:: C
 
@@ -1394,6 +1394,9 @@ Broadcast.
     MPI_Bcast(buf1, buff_size, MPI_CHAR, 0, newcom);
   }
 
+The barrier is only simulated and does not involve any additional message (it is a S4U barrier).
+This option is disabled by default, and activated by the `-analyze` flag of smpirun.
+
 .. _cfg=smpi/barrier-finalization:
 
 Add a barrier in MPI_Finalize