Clarify one paragraph in the doc

diff --git a/docs/source/Configuring_SimGrid.rst b/docs/source/Configuring_SimGrid.rst
index f581710..029884c 100644 (file)
--- a/docs/source/Configuring_SimGrid.rst
+++ b/docs/source/Configuring_SimGrid.rst
@@ -965,9 +965,14 @@ this into account. For that, the actual duration is measured on the
 host machine and then scaled to the power of the corresponding
 simulated machine. The variable ``smpi/host-speed`` allows one to
 specify the computational speed of the host machine (in flop/s by
 host machine and then scaled to the power of the corresponding
 simulated machine. The variable ``smpi/host-speed`` allows one to
 specify the computational speed of the host machine (in flop/s by

-default) to use when scaling the execution times. It defaults to 20kf
-(i.e., 20000 flop/s), but you really want to adjust it to get accurate
-simulation results.
+default) to use when scaling the execution times.
+
+The default value is ``smpi/host-speed=20kf`` (= 20,000 flop/s). This
+is probably underestimated for most machines, leading SimGrid to
+overestimate the amount of flops in the execution blocks that are
+automatically injected in the simulator. As a result, the execution
+time of the whole application will probably be overestimated until you
+use a realistic value.

 
 When the code consists of numerous consecutive MPI calls, the
 previous mechanism feeds the simulation kernel with numerous tiny
 
 When the code consists of numerous consecutive MPI calls, the
 previous mechanism feeds the simulation kernel with numerous tiny