Solve a system with two processors
Hello PETSc's users! I have a problem with my parallel program. If I run it with only one processor (mpirun -np 1...), everything is all right but if I use 2 processors (mpi -np 2...), the problem appears. When I want to solve my matricial system through a solver, after having created my matrices without any hitch, I have the following problem: The two processes that are running in two different processors using 100% of CPU and 14.6% of memory each of them, end up using 0% of CPU and 14.6% of memory and, although the program doesn't break down, both of the processes don't do anything. This looks like a lockup: one processor is waiting for a message from the second one, but the second one thinks that it doesn't have to send anything and is instead waiting for something else from the first processor. But I don't know how to avoid this problem since it is supposed that I don't have to use MPI_Send() and MPI_Recv() functions because PETSc itself deals with it, do I?. Any advice will be welcome. Thanks in advance and best regards Isa
Solve a system with two processors
Isa, The PETSc solvers are all deadlock free, this means that if used with a proper MPI implementation it will never deadlock inside the solvers. The easiest way (and best and the one you should use) to determine what is causing the problem is to use the additional option -start_in_debugger when the two xterms popup then type cont in both debuggers, wait and wait until you think it is stuck and then do control-c in each window and then where, it will show you exactly where it is hanging. (Do this with the debug version of PETSc, that is config/configure.py should not be run with --with-debugging=0. Good luck, Barry Should become a FAQ question On Tue, 9 Jan 2007, Isabel Gil wrote: Hello PETSc's users! I have a problem with my parallel program. If I run it with only one processor (mpirun -np 1...), everything is all right but if I use 2 processors (mpi -np 2...), the problem appears. When I want to solve my matricial system through a solver, after having created my matrices without any hitch, I have the following problem: The two processes that are running in two different processors using 100% of CPU and 14.6% of memory each of them, end up using 0% of CPU and 14.6% of memory and, although the program doesn't break down, both of the processes don't do anything. This looks like a lockup: one processor is waiting for a message from the second one, but the second one thinks that it doesn't have to send anything and is instead waiting for something else from the first processor. But I don't know how to avoid this problem since it is supposed that I don't have to use MPI_Send() and MPI_Recv() functions because PETSc itself deals with it, do I?. Any advice will be welcome. Thanks in advance and best regards Isa
Using library from another linux system
On Wed, 10 Jan 2007, Ben Tay wrote: Hi, I've some problems compiling PETSC on one of my school's server. send us configure.log at petsc-maint at mcs.anl.gov and we take a look at the problem. Its probably easier to get this working than trying the alternatives below.. I've already compiled a working library on another linux system. Is it possible for me to just copy the library from one to another. They are both redhat linux system and I think they're running on xeon processors. What are the things which I must looked out for? e.g. directory location etc... It might work [see notes below] Can the compiler be of different version? The server I compiled on uses ifort 9 or 7 while on the problem system ifort 8 is used. yeah difference in compiler verson can cause problems.. [I'm not sure if there are issues between these intel compiler versions]. If it were to work - you can copy the whole petsc tree with 'rsync -a' Can the original library be shared or must it be static? If PETSc was configured with Sharedlibs, there could be issues after the move. Rebuilding sharedlibs might work arround this problem.. make deleteshraed shared There could also be issues with external libraries. They need to exist on the other machine - in the exact same location as the first one. [otherwise you will get errors at compile time. Satish
