Thanks Patrice. I will be trying it out hopefully nextweek. Also, If we are writing ECAT7 output along with the root where else would I need to make changes?? Just one more question, see below <div>On 11/1/05, patrice descourt <<a href="mailto:patrice.descourt@univ-brest.fr"> patrice.descourt@univ-brest.fr</a>> wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Dear Vandana you do not have to bother about installing geant or gate on each node, MPI logs on each node via rsh or ssh depending on your parameterization. Below are outlines along which you can get parallel jobs I will be pleased to give the final codes in a directory when I have written those because for now I only focus on the second implementation which is far more cumbersome. The first one should not present any problems : You just have to install MPI and compile Geant and Gate with mpicc which replaces gcc and run Gate via mpirun : mpirun -np #number of nodes  your_compiled_code.exe you have to include #include "mpi.h"  in each file using MPI library e.g Gate.cc and G4RunManager.hh >>>Are these the only two files where we have to include "mpi.h" ??? In Gate.cc you need at the beginning of main() to add MPI::Init(argc,argv);   : this is to initialize MPI at the end of Gate.cc main() you put MPI::Finalize(); in G4RunManager::DoEventLoop() you put G4int proc_number = MPI::COMM_WORLD.Get_size(); G4int proc_ID = MPI::COMM_WORLD.Get_rank(); before the for loop which you replace with for(i_event = proc_ID; i_event<n_event; i_event += proc_number) now for the output,  I review the ROOT one but the scheme is the same for any GateVOutputModule : in GateToRoot.hh you put #include "mpi.h" and put at the beginning of GateToRoot:RecordBeginOfAcquisition G4int proc_ID = MPI::COMM_WORLD.Get_rank(); and replace each GetFilePath() by  GetFilePath()+"proc_"+proc_ID I will give all the codes when this is all implemented Cheers P.Descourt _______________________________________________ gate-users mailing list <a href="mailto:gate-users@lphe1pet1.epfl.ch">gate-users@lphe1pet1.epfl.ch </a> <a href="http://lphe1pet1.epfl.ch/mailman/listinfo/gate-users">http://lphe1pet1.epfl.ch/mailman/listinfo/gate-users</a> </blockquote></div>