Commit 4fb0efea authored by thakur's avatar thakur
Browse files

added info on optimization level

parent b1c7e2da
......@@ -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
============================
......
......@@ -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}
......
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