<laugh> I never argue the standard with George, so I'll take his word for it.
I tried your program and it worked just fine for me without the sleep. However,
I still think there is something wrong in it. I tried adjusting the number of
processes and that caused it to hang, for one. Afraid I don't have time to
debug it further, but can only suggest you take the code I sent you as a
working example to use in your debugging.
On Aug 31, 2014, at 11:02 PM, George Bosilca <bosi...@icl.utk.edu> wrote:
> Based on the MPI standard (MPI 3.0 section 10.5.4 page 399) there is no need
> to disconnect the child processes from the parent in order to cleanly
> finalize. From this perspective, the original example is correct, but
> sub-optimal as the parent processes calling MPI_Finalize might block until
> all connected processes (in this case all the children processes) will call
> MPI_Finalize. To be more precise, the disconnect has a single role to
> redivide the application in separated groups of connected processes in order
> to prevent error propagation (such as MPI_Abort).
>
> George.
>
>
>
> On Mon, Sep 1, 2014 at 12:58 AM, Ralph Castain <r...@open-mpi.org> wrote:
> You need to disconnect the parent/child from each other prior to finalizing -
> see the attached example
>
>
>
>
> On Aug 31, 2014, at 9:44 PM, Roy <open...@jsp.selfip.org> wrote:
>
> > Hi all,
> >
> > I'm using MPI_Comm_spawn to start new child process.
> > I found that if the parent process execute MPI_Finalize before the child
> > process, the child process core dump on MPI_Finalize.
> >
> > I couldn't find the correct way to have a clean shutdown of all processes
> > ( parent and child ).
> > What that I found is that sleep(2) in the parent process just before
> > calling MPI_Finalize, gives the CPU cycle for the child process to finish
> > its own MPI_Finalize, and only then there is no core dump.
> >
> > Although this resolve the issue, I can't accept this as acceptable solution.
> >
> > I guess I'm doing something wrong ( implementation or design ), so this is
> > why I'm sending this email to the group ( and yes, I did check the FAQ,
> > and done some search on the distribution list archive ).
> >
> > Here is the entire code to reproduce the issue :
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > #include <stdio.h>
> > #include <string.h>
> > #include <unistd.h>
> > #include <mpi.h>
> > #include <stdlib.h>
> >
> > int main(int argc, char* argv[]){
> > int my_rank; /* rank of process */
> > int p; /* number of processes */
> > int source; /* rank of sender */
> > int dest; /* rank of receiver */
> > int tag=0; /* tag for messages */
> > char message[100]; /* storage for message */
> > MPI_Status status ; /* return status for receive */
> >
> > /* start up MPI */
> >
> > MPI_Init(&argc, &argv);
> >
> > /* find out process rank */
> > MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
> > fprintf(stderr,"My rank is : %d\n",my_rank);
> > /* find out number of processes */
> > MPI_Comm_size(MPI_COMM_WORLD, &p);
> >
> > MPI_Comm parent;
> > MPI_Comm_get_parent(&parent);
> >
> > if ( parent != MPI_COMM_NULL){
> > /* create message */
> > dest = 0;
> > /* use strlen+1 so that '\0' get transmitted */
> >
> > MPI_Recv(message, 100, MPI_CHAR, 0, tag,parent, &status);
> > fprintf(stderr,"Got [%s] from root\n",message);
> > /* shut down MPI */
> > MPI_Finalize();
> >
> > }
> > else{
> > printf("Hello MPI World From process 0: Num processes:
> > %d\n",p);
> > MPI_Comm everyone;
> > MPI_Comm_spawn("mpitest",MPI_ARGV_NULL,1,MPI_INFO_NULL,0,
> > MPI_COMM_SELF,&everyone,
> > MPI_ERRCODES_IGNORE);
> > /* find out number of processes */
> > MPI_Comm_size(everyone, &p);
> > fprintf(stderr,"New world size:%d\n",p);
> > for (source = 0; source < p; source++) {
> > sprintf(message, "Hello MPI World from root to
> > process %d!", source);
> > MPI_Send(message, strlen(message)+1, MPI_CHAR,source,
> > tag, everyone);
> > }
> >
> > /**
> > * Why this sleep resolve my core dump issues ?
> > * Any timing between the parent to child process ?
> > * Based on the document, and FAQ, I couldn't not find an
> > answer for
> > this issue.
> > *
> > * If you comment out the sleep(2), the child process will
> > crash on the
> > MPI_Finalize with
> > * singal 11, Segmentation fault.
> > */
> > //sleep(2); //un-comment this line to have the sleep, and
> > avoid the core
> > dumps.
> >
> > /* shut down MPI */
> > MPI_Finalize();
> >
> > }
> > return 0;
> > }
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Anyone for the rescue ?
> >
> >
> > Thank you,
> > Roy Avidor
> > _______________________________________________
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> > us...@open-mpi.org
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> > Searchable archives:
> > http://www.open-mpi.org/community/lists/users/2014/09/index.php
>
>
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