MPICH2 on single machine

Accelerated Computing HPC Compilers Legacy PGI Compilers
#1

I have a single machine with 2 CPU, each with 4 cores. May I assk how could I configure to get it work with multiple processes. I always get the following message

mpdboot -n 4 -f ~/mpd.hosts_cardiac
totalnum=4 numhosts=1
there are not enough hosts on which to start all processes

Thanks,
Tuan

#2

Hi Tuan,

What’s your “machine.LINUX” file look like? Do you list your host 8 times in it or put a “:8” after the name to let the mpdboot know you have 8 cores on this system?

  • Mat
#3

I list my hostname 8 times. I guess the mpdboot only allow each hostname to occur once.

Tuan

#4

Hi,

For MPICH2, you need to start only one daemon per machine. Once the daemon started, then you can run multiple processes.

% mpdboot
%mpiexec -np 2 a.out
%mpdallexit



If you have more than one machine, put all hosts in mpd.hosts and then invoke:
%mpdboot --totalnum=3

where 3 is a number of hosts in mpd.hosts file.

% mpdtrace # test if all hosts list in mpd.hosts starts the daemon

Hongyon

#5

Thanks, Hongyon.

A simple test case on a single-host cluster seem to work. However, when I add collective communication call, MPI_Bcast. It doesn’t work. The error output is

$mpdboot
minhtuan@cardiac:\ $mpiexec -n 3 ./vect
Time to initialize MPI is 0
FORTRAN STOP
FORTRAN STOP
End test
FORTRAN STOP
rank 2 in job 1 cardiac.binf_57734 caused collective abort of all ranks
exit status of rank 2: return code 0
rank 1 in job 1 cardiac.binf_57734 caused collective abort of all ranks
exit status of rank 1: return code 0
rank 0 in job 1 cardiac.binf_57734 caused collective abort of all ranks
exit status of rank 0: return code 0

The test code is given

  IMPLICIT NONE
  INCLUDE 'mpif.h'
  
  
  INTEGER :: mpierror, numprocs, myrank
  DOUBLE PRECISION :: mytime, maxtime, mintime, avgtime
  INTEGER :: count0, count1, count_max, count_rate, dtime
  LOGICAL :: flag
  INTEGER :: data
  CHARACTER (MPI_MAX_ERROR_STRING+1) :: err_msg
  
  CALL MPI_Initialized(flag, mpierror)
  IF (.NOT. flag)  THEN
     ! start timer
     CALL SYSTEM_CLOCK(count0, count_rate, count_max)
     CALL MPI_Init(mpierror)
     IF( mpierror .NE. MPI_SUCCESS) THEN
        PRINT *, "Error Init MPI"
        STOP
     END IF
     CALL MPI_Comm_Size(MPI_COMM_WORLD, numprocs, mpierror)
     IF( mpierror .NE. MPI_SUCCESS) THEN
        PRINT *, "Error Detect Communicator size"
        STOP
     END IF

     CALL MPI_Comm_Rank(MPI_COMM_WORLD, myrank, mpierror)
     IF( mpierror .NE. MPI_SUCCESS) THEN
        PRINT *, "Error Detect process rank"
        STOP
     END IF
     
     ! stop timer
     CALL SYSTEM_CLOCK(count1, count_rate, count_max)
     dtime = (count1-count0)/count_rate
     ! end timer
  END IF
  IF (myrank .EQ. 0) THEN
     PRINT *, "Time to initialize MPI is ", dtime
     ! initialize
     data = 1000
  ENDIF
  CALL MPI_Bcast(data, 1, MPI_INTEGER, 0, MPI_COMM_WORLD, mpierror)
  IF( mpierror .NE. MPI_SUCCESS) THEN
     PRINT *, "Error Broadcast message"
     STOP
  END IF
  
  CALL MPI_Barrier(MPI_COMM_WORLD, mpierror)
  IF( mpierror .NE. MPI_SUCCESS) THEN
     PRINT *, "Error Barrier"
     STOP
  END IF
  
  IF (myrank .EQ. 0) THEN
     PRINT *, "End test"
  END IF
  STOP

Thanks,
Tuan

#6

Remove the last “STOP” statement from your program and add a call to MPI_FINALIZE(some_integer).


Here is more information about MPI:

http://www.mcs.anl.gov/research/projects/mpi/


Hongyon

#7

Thanks, Hongyon. I forgot to add that in the sample code, but in the real code it does have the finalization statement.

I realize one issue, the call to flush() statement (without any argument) doesn’t work properly in MPICH2. It causes the error that I mentioned above. It works if a given device ID is passed as the input. Could you please confirm this.

Thanks,
Tuan

#8

Hi,

Yes, you will need to give the file unit as an argument.

Hongyon

#9

thanks. Hongyon. Did you get any forwarded email from trs. Could you please check and help me to resolve my network problem when I run MPICH2 on a cluster, not a single host machine.

Tuan