[MPICH] Is ther a limitation with MPI_Comm_spawn_multiple

[Rajesh Sudarsan]

Hi Rajeev,
Thanks for the reply. But the same code runs perfectly if num = 4 or 
less. In the example I sent you, the value of num =8 and I had assigned 
memory from 0 to 7. I tried running this code with different value of 
num and it gave the same results. I also thought there is no restriction 
on comm_spawn_multiple command, but I cannot understand why this simple 
code is not working. I dont think it is because of memory allocation.

Regards,
Rajesh

Rajeev Thakur wrote:
> 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
>>
>>
>>     
>
>
>