[mpich-discuss] ADIOI_Set_lock error

[Rob Latham]

On 11/01/2016 10:00 AM, Luke Van Roekel wrote:
> Thanks Rob, no luck with the mpi_info object and our computing folks are
> not willing to set the necessary option.  Do you know why this is
> specific to intel-mpi?  Openmpi has no issue.  Our HPC people thought
> the MPI_File_write_at_all always requires a file lock, but openmpi seems
> to be fine.

I don't think the collectives (routines ending in _all) will trigger a 
lock request.   ROMIO makes a lock request to guard against false 
sharing when performing a data sieving write

it's called data sieving but it's actually a read-modify-write and we 
need to protect against two processes doing partial updates of the same 
region.

OpenMPI has a different MPI-IO implementation as of I think 1.10.  I 
don't know what optimizations they implement or how they avoid false 
sharing.

==rob



>
> On Tue, Nov 1, 2016 at 8:42 AM, Rob Latham <robl at mcs.anl.gov
> <mailto:robl at mcs.anl.gov>> wrote:
>
>
>
>     On 10/31/2016 11:47 PM, Luke Van Roekel wrote:
>
>         Hello,
>
>         I've been trying to compile and run a very simple mpi test on our
>         cluster with intel-mpi and openmpi.  The test program is below.
>         When I
>         run with openmpi everything is fine.  When I run with intel-mpi, I
>         receive the following error
>
>         This requires fcntl(2) to be implemented. As of 8/25/2011 it is not.
>         Generic MPICH Message: File locking failed in ADIOI_Set_lock(fd
>         6,cmd
>         F_SETLKW/7,type F_WRLCK/1,whence 0) with return value FFFFFFFF
>         and errno 26.
>
>
>
>         - If the file system is NFS, you need to use NFS version 3,
>         ensure that
>         the lockd daemon is running on all the machines, and mount the
>         directory
>         with the 'noac' option (no attribute caching).
>
>         - If the file system is LUSTRE, ensure that the directory is mounted
>         with the 'flock' option.
>
>         ADIOI_Set_lock:: Function not implemented
>
>         ADIOI_Set_lock:offset 0, length 4
>
>
>
>     your site administrator needs to enable fcntl locking with the
>     'flock' mount option .
>
>     You can try disabling data sieving:  you would create an MPI_Info
>     object and add the key "romio_ds_write" with the value "disable"
>
>     ==rob
>
>
>
>         Any thoughts on how to proceed?  The size/format of the file read in
>         seems to make no difference.
>
>         Regards,
>         Luke
>
>
>          #include <stdio.h>
>
>          #include <stdlib.h>
>
>          #include <mpi.h>
>
>
>
>           int main(int argc, char **argv) {
>
>             int buf, err;
>
>             MPI_File fh;
>
>             MPI_Status status;
>
>
>             MPI_Init(&argc, &argv);
>
>             if (argc != 2) {
>
>                 printf("Usage: %s filename\n", argv[0]);
>
>                 MPI_Finalize();
>
>                 return 1;
>
>             }
>
>             err = MPI_File_open(MPI_COMM_WORLD, argv[1], MPI_MODE_CREATE |
>
>                                 MPI_MODE_RDWR, MPI_INFO_NULL, &fh);
>
>             if (err != MPI_SUCCESS) printf("Error: MPI_File_open()\n");
>
>
>             err = MPI_File_write_all(fh, &buf, 1, MPI_INT, &status);
>
>             if (err != MPI_SUCCESS) printf("Error: MPI_File_write_all()\n");
>
>
>             MPI_File_close(&fh);
>
>             MPI_Finalize();
>
>             return 0;
>
>         }
>
>
>
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