[MPICH] Is ther a limitation with MPI_Comm_spawn_multiple

[Rajeev Thakur]

I haven't run your code, but I don't think you have allocated enough memory
in the commands array to do this:

>        commands=(char**)malloc(sizeof(char)*num);
>        commands[0]="./hello";
>        commands[1]="./hello";
>        commands[2]="./hello";
>        commands[3]="./hello";
>        commands[4]="./hello";
>        commands[5]="./hello";
>        commands[6]="./hello";
>        commands[7]="./hello";
 
There is no limit in comm_spawn_multiple.

Rajeev


> -----Original Message-----
> From: owner-mpich-discuss at mcs.anl.gov 
> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Rajesh Sudarsan
> Sent: Wednesday, April 05, 2006 6:15 PM
> To: mpich-discuss at mcs.anl.gov
> Subject: [MPICH] Is ther a limitation with MPI_Comm_spawn_multiple
> 
> Hi,
> I am using the MPI_Comm_spawn_multiple command in my program to 
> dynamically spawn new processes. But the command does not 
> seem to work 
> when the number of spawned processes is greater than or equal to 5. I 
> tested this using a simple master worker example. I have pasted the 
> sample programs below. Could anyone tell me where I am going 
> wrong or is 
> this a limitation with the implementation?
> 
> MASTER:
> 
> #include<string.h>
> #include<stdlib.h>
> #include<stdio.h>
> #include <mpi.h>
> 
> void
> main(int argc, char **argv)
> {
> 
>         int             tag = 0;
>         int             my_rank;
>         int             num_proc;
>         char         slave[20];
>         int             array_of_errcodes[10];
>         int             num,k;
>         MPI_Status      status;
>         MPI_Comm        inter_comm;
>         char **commands;
>         MPI_Info *info;
>         int *maxprocs;
>         char ***args=NULL;
>         int i=1;   
>      
>         char *host =(char*)"host";
> 
>        num = 8;
> 
>        commands=(char**)malloc(sizeof(char)*num);
>        commands[0]="./hello";
>        commands[1]="./hello";
>        commands[2]="./hello";
>        commands[3]="./hello";
>        commands[4]="./hello";
>        commands[5]="./hello";
>        commands[6]="./hello";
>        commands[7]="./hello";
> 
>         maxprocs=(int *)malloc(sizeof(int)*num);
>         maxprocs[0]=i;
>         maxprocs[1]=i;
>         maxprocs[2]=i;
>         maxprocs[3]=i;
>         maxprocs[4]=i;
>         maxprocs[5]=i;
>         maxprocs[6]=i;
>         maxprocs[7]=i;
>  
>  
>         MPI_Init(&argc, &argv);
>         MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
>         MPI_Comm_size(MPI_COMM_WORLD, &num_proc);
> 
>         info=(MPI_Info *)malloc(sizeof(MPI_Info)*num);
>         MPI_Info_create (&info[0]);
>         MPI_Info_create (&info[1]);
>         MPI_Info_create (&info[2]);
>         MPI_Info_create (&info[3]);
>         MPI_Info_create (&info[4]);
>         MPI_Info_create (&info[5]);
>         MPI_Info_create (&info[6]);
>         MPI_Info_create (&info[7]);
> 
> 
>         MPI_Info_set (info[0],host, "n1026");
>         MPI_Info_set (info[1],host, "n1027");
>         MPI_Info_set (info[2],host, "n1028");
>         MPI_Info_set (info[3],host, "n1029");
>         MPI_Info_set (info[4],host, "n1050");
>         MPI_Info_set (info[5],host, "n1051");
>         MPI_Info_set (info[5],host, "n1052");
>         MPI_Info_set (info[5],host, "n1053");
> 
> 
>     printf("Master %d running on host\n",my_rank);
>     printf("MASTER : spawning  %d slaves ... \n",num);
>    
>         /* spawn slave and send it a message */ 
>     MPI_Comm_spawn_multiple(num, commands, args, maxprocs, info,0, 
> MPI_COMM_WORLD, &inter_comm, array_of_errcodes);
> 
>      MPI_Finalize();
> 
> }
> 
> 
> WORKER:
> 
> #include <stdio.h>
> #include <mpi.h>
> 
> main (int argc, char **argv)
> {
>    int node,k;
>    int data1[1],data2[1]=10;
>    MPI_Status *status;
>    char host[20];
>    MPI_Init(&argc, &argv);
>    MPI_Comm_rank(MPI_COMM_WORLD, &node);
> 
>     status = (MPI_Status*)malloc(sizeof(MPI_Status));
> 
>    if (node == 0) {
>      printf("Rank 0 is present in C version of Hello World.\n");
>      k=gethostname(host,20);
>      printf("hostname = %s\n",host);
>      data1[1]=11;
>       printf("data received on proc %d\n",node);
>        printf("%d\n",data2[1]);
>    }
>     else {
>      k=gethostname(host,20);
>      printf("hostname = %s\n",host);
>      data1[1]=16;
>      printf("  Rank %d of C version says: Hello world!\n", node);
>      printf("data received on proc %d\n",node);
>      printf("-- %d\n",data2[1]);
>    }
> 
>     MPI_Finalize();
> }
> 
> 
> Regards,
> Rajesh Sudarsan
> 
>