added info on optimization level

README

@@ -239,9 +239,11 @@ later, in the section "Alternative configurations".
     mpdboot and other options for starting the mpd's are in
     mpich2-1.0.6/src/pm/mpd/README.
 
+ !! ***************************
     If you are still having problems getting the mpd ring established,
-    see the Installation Guide for instructions on how to diagnose
-    problems with your system configuration that may be preventing it.
+    you can use the mpdcheck utility as described in the Installation Guide 
+    to diagnose problems with your system configuration.
+ !! ***************************
 
 12. Test the ring you have just created:
 
@@ -342,6 +344,24 @@ in the mpich2 directory.  The alternatives described below are
 configured by adding arguments to the configure step.
 
 
+Compiler Optimization Levels
+============================
+
+By default, from version 1.0.6 onwards the MPICH2 library is built
+with the -O2 optimization level if it is available. The mpicc and
+other scripts that are used to compile applications do not include any
+optimization flag by default. If you want to build the MPICH2 library
+with a specific optimization level, set the environment variable
+CFLAGS to that level before running configure. If you do not want this
+CFLAGS value to be included in the mpicc script, set the environment
+variable MPI_CFLAGS to MPI_CFLAGS_EMPTY. For example, to build a
+"production" MPICH2 in a GNU environment, you may want to do:
+     setenv CFLAGS -O3
+     setenv MPI_CFLAGS MPI_CFLAGS_EMPTY
+before running configure. This will cause the MPICH2 library to be
+built with -O3, but -O3 will not be included in the mpicc script.
+
+
 Alternative Process Managers
 ============================
 

doc/installguide/install.tex

@@ -383,11 +383,12 @@ to see which machines are in the ring so far.  More details on
 \texttt{mpdboot} and other options for starting the mpd's are in
 \texttt{mpich2-1.0.6/src/pm/mpd/README}.
 
-In case of persistent difficulties getting the ring of mpd's up and
-running on the machines you want, please see Appendix~\ref{app:mpd}.
-There we discuss the mpd's in more detail, together with some programs
-for testing the configuration of your systems to make sure that they
-allow the mpd's to run.
+{\em In case of persistent difficulties getting the ring of mpd's up
+and running on the machines you want, please see
+Appendix~\ref{app:mpd}.  There we discuss the mpd's in more detail and
+describe how you can use the \texttt{mpdcheck} utility to diagnose
+problems with the networking configuration of your systems.}
+
 
 \item
 Test the ring you have just created:
@@ -479,6 +480,24 @@ If you have completed all of the above steps, you have successfully
 installed MPICH2 and run an MPI example.  
 
 
+\subsection{Compiler Optimization Levels}
+From version 1.0.6 onwards, by default, the MPICH2 library is built
+with the -O2 optimization level if it is available. The mpicc and
+other scripts that are used to compile applications do not include any
+optimization flag by default. If you want to build the MPICH2 library
+with a specific optimization level, set the environment variable
+\texttt{CFLAGS} to that level before running configure. If you do not want this
+\texttt{CFLAGS} value to be included in the mpicc script, set the environment
+variable \texttt{MPI\_CFLAGS} to \texttt{MPI\_CFLAGS\_EMPTY}. For example, to build a
+``production'' MPICH2 in a GNU environment, you may want to do:
+\begin{verbatim}
+     setenv CFLAGS -O3
+     setenv MPI_CFLAGS MPI_CFLAGS_EMPTY
+\end{verbatim}
+before running configure. This will cause the MPICH2 library to be
+built with -O3, but -O3 will not be included in the mpicc script.
+
+
 \subsection{Common Non-Default Configuration Options}
 \label{sec:non-default}