When porting music to a new machine, the following things needs to be
taken into consideration:


1. Regeneration of the configure script

The script ./autogen.sh is used to generate/regenerate the configure
script. For this to work, the GNU autotools (autoconf, automake and
libtool) need to be installed.


2. Compilation and linking flags

configure.ac contains mechanisms which try to identify which MPI
implementation/environment is in use and, based on this, decide
automagically which compiler, compilation flags and linking flags to
use. To circumvent, pass variable definitions ro configure, e.g.:

  ./configure MPI_CXXFLAGS="-g -O3 -Wall -pedantic"

The variables are:

MPI_CXX       The compiler to use for MPI code
MPI_CXXFLAGS  C++ compilation flags
MPI_CFLAGS    C compilation flags
MPI_LDFLAGS   Linking flags


3. MPI implementation dependent code

MUSIC depends on two MPI implementation dependent functions: getRank,
which predicts the rank a process is going to be assigned when
executing MPI_Init, and getConfig, which determines the first command
line argument to the music launch utility "music" (also before having
executed MPI_Init.


4. Alternative launch method

On some computers, the standard MUSIC launch method (using the music
utility) does not work, either because it is difficult to supply an
implementation of the functions mention under point 3 above, or
because the compute node OS does not support the system call execvp
used by the music launch utility to replace its image with one of the
binaries in the multi-simulation.

In such cases, it is possible to launch the multi-simulation as an
MPMD/MIMD program. Example: If we have a MUSIC configuration file
myconfig.music, defining two applications named A and B, the standard
way to launch the multi-simulation is:

  mpirun -np N music myconfig.music

where N is the number of processes needed (as specified in
myconfig.music) by the multi-simulation. Using the alternative method,
one first issues the command line:

  music -e myconfig.music

This will write one shell script per application into the current
working directory, in this case A.sh and B.sh. These scripts can then
by used to launch the multi-simulation. Under OpenMPI, the command
line would be:

  mpirun -np NA A.sh : -np NB B.sh

where NA and NB are the number of processes needed (and specified in
myconfig.music) by the applications A and B respectively.

On a machine where the architecture of the login node differs from the
architecture of the compute nodes, it is sometimes convenient to be
able to compile the music launch utility without MPI support on the
login node in order to be able to use the -e option. This is
convenient, for example if the login node is running a script which
prepares jobs to be executed on the compute nodes.  If you need to do
this, MUSIC can be configured without MPI:

  ./configure --disable-mpi