[Neolith-users] Updated information about Scali MPI

[Mattias Slabanja]

To all Neolith test users.

1. No Scali MPI until next week

I regret to inform you that we will have to do without a new Scali 
license until some day next week. It is a consequence of Neolith still 
being in test phase.


2. Alternatives to Scali MPI

Until we have the new license, please try out Open MPI, which is also 
installed on the system.
The procedure to build a program with Open MPI is identical to building 
with Scali MPI; just make sure to have the openmpi-module loaded.
For example, if using the intel C-compiler, icc.

$ module load openmpi
$ icc -Nmpi -o hello hello.c
icc INFO: Linking with MPI openmpi/1.2.4-i100026.

The binary 'hello' can now be started with mpprun as usual.


3. Further information about -Nmpi

If you would like to now more about what happens when using the flag 
-Nmpi, add also the flag -Nverbose. Enabling -Nverbose makes the 
compiler wrapper display more verbose information about what it does.
N.b. -Nmpi will do different things depending on which mpi-module is 
currently loaded and depending on which compiler you are using.
For example.

$ module load openmpi
$ icc -Nverbose -Nmpi -o hello hello.c
icc INFO: Linking with MPI openmpi/1.2.4-i100026.
icc INFO: -Nmpi resolved to: 
-I/software/mpi/openmpi/1.2.4/i100026/include -pthread 
-L/software/mpi/openmpi/1.2.4/i100026/lib -lmpi -lopen-rte -lopen-pal 
-ldl -Wl,--export-dynamic -lnsl -lutil 
-Wl,--rpath,/software/mpi/openmpi/1.2.4/i100026/lib

Also remember that the compiler wrapper will display a help summary if 
given the flag -Nhelp.


Best regards,
Mattias Slabanja
NSC