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Subject: Re: [OMPI users] error performing MPI_Comm_spawn
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-12-15 09:58:10


Looks to me like it is a race condition, and the timing between 1.3.3 and 1.4 is just enough to trip it. I can break the race, but it will have to be in a future fix release.

Meantime, your best bet is to either stick with 1.3.3 or add the delay.

On Dec 15, 2009, at 5:51 AM, Marcia Cristina Cera wrote:

> Hi,
>
> I intend to develop an application using the MPI_Comm_spawn to create dynamically new MPI tasks (or processes).
> The structure of the program is like a tree: each node creates 2 new ones until reaches a predefined number of levels.
>
> I developed a small program to explain my problem as can be seen in attachment.
> -- start.c: launches (through MPI_Comm_spawn, in which the argv has the level value) the root of the tree (a ch_rec program). Afterward spawn, a message is sent to child and the process block in an MPI_Recv.
> -- ch_rec.c: gets its level value and receives the parent message, then if its level is less than a predefined limit, it will creates 2 children:
> - set the level value;
> - spawn 1 child;
> - send a message;
> - call an MPI_Irecv;
> - repeat the 4 previous steps for the second child;
> - call an MPI_Waitany waiting for children returns.
> When children messages are received, the process send a message to its parent and call MPI_Finalize.
>
> Using the openmpi-1.3.3 version the program runs as expected but with openmpi-1.4 I get the following error:
>
> $ mpirun -np 1 start
> level 0
> level = 1
> Parent sent: level 0 (pid:4279)
> level = 2
> Parent sent: level 1 (pid:4281)
> [xiru-8.portoalegre.grenoble.grid5000.fr:04278] [[42824,0],0] ORTE_ERROR_LOG: Not found in file base/plm_base_launch_support.c at line 758
>
> The error happens when my program try to launch the second child immediately after the first spawn call.
> In my tests I try to put an sleep of 2 second between the first and the second spawn, and then the program runs as expected.
>
> Some one can help me with this version 1.4 bug?
>
> thanks,
> márcia.
>
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