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Subject: [OMPI users] mpi test program "ring" failed: blocked at MPI_Send
From: Richard (codemonkee_at_[hidden])
Date: 2012-09-25 06:51:47


I have setup a small cluster with 3 nodes, named A, B and C respectively.
I tested the ring_c.c program in the examples. For debugging purpose,
I have added some print statements as follows in the original ring_c.c
>> 60 printf("rank %d, message %d,start===========\n", rank, message);
>> 61 MPI_Send(&message, 1, MPI_INT, ! next, tag, MPI_COMM_WORLD);
>> 62 printf("rank %d, message %d,end-------------\n", rank, message);
I lauched my mpi program as follows:
$mpirun -np 3 --hostfile myhostfile ./ring
the content in myhost file is:
=========
hostA slots=1
hostB slots=1
hostC slots=1
============
I got the follow output:
==========================
Process 0 sending 10 to 1, tag 201 (3 processes in ring)
Process 0 sent to 1
rank 1, message 10,start===========
rank 1, message 10,end-------------
rank 2, message 10,start===========
Process 0 decremented value: 9
rank 0, message 9,start===========
rank 0, message 9,end-------------
rank 2, message 10,end-------------
rank 1, message 9,start===========
=========================
I assumed there is communication problem between B and C, so I launched the program with 2 processes on B and C.
the output is as follows:
===============
Process 0 sending 10 to 1, tag 201 (2 processes in ring)
Process 0 sent to 1
rank 1, message 10,start===========
rank 1, message 10,end-------------
Process 0 decremented value: 9
rank 0, message 9,start===========
===============
Again, in the second round of pass, B failed to send message to C.
I checked firewall config using chkconfig --list iptables on all the nodes. none of them are set as "on".

Attached is all the information needed, my openmpi version is 1.6.1.

thanks for your help.
Richard

At 2012-09-25 18:27:15,Richard <codemonkee_at_[hidden]> wrote:

I used "chkconfig --list iptables ", none of computer is set as "on".

At 2012-09-25 17:54:53,"Jeff Squyres" <jsquyres_at_[hidden]> wrote:

>Hav you disabled firewalls on your nodes (e.g., iptables)?
>
>On Sep 25, 2012, at 11:08 AM, Richard wrote:
>
>> sometimes the following message jumped out when I run the ring program, but not always.
>> I do not know this ip address 192.168.122.1, it is not in my list of hosts.
>>
>>
>> [[53402,1],6][btl_tcp_endpoint.c:638:mca_btl_tcp_endpoint_complete_connect] connect() to 192.168.122.1 failed: Connection refused (111
>>
>>
>>
>>
>>
>> At 2012-09-25 16:53:50,Richard <codemonkee_at_[hidden]> wrote:
>>
>> if I tried the ring program, the first round of pass is fine, but the second round is blocked at some node.
>> here is the message printed out
>>
>> Process 0 sending 10 to 1, tag 201 (3 processes! in ring)
>> Process 0 sent to 1
>> rank 1, message 10,start===========
>> rank 1, message 10,end-------------
>> rank 2, message 10,start===========
>> Process 0 decremented value: 9
>> rank 0, message 9,start===========
>> rank 0, message 9,end-------------
>> rank 2, message 10,end-------------
>> rank 1, message 9,start===========
>>
>> I have added some printf statements in the ring_c.c as follows:
>> 60 printf("rank %d, message %d,start===========\n", rank, message);
>> 61 MPI_Send(&message, 1, MPI_INT, ! next, tag, MPI_COMM_WORLD);
>> 62 printf("rank %d, message %d,end-------------\n", rank, message);
>>
>>
>>
>> At 2012-09-25 16:30:01,Richard <codemonkee_at_[hidden]> wrote:
>> Hi Jody,
>> thanks for your suggestion and you are right. if I use the ring example, the same happened.
>> I have put a printf statement, it seems that all the three processed have reached the line
>> calling "PMPI_Allreduce", any further suggestion?
>>
>> Thanks.
>> Richard
>>
>>
>>
>> Message: 12
>> Date: Tue, 25 Sep 2012 09:43:09 +0200
>> From: jody <
>> jody.xha_at_[hidden]
>> >
>> Subject: Re: [OMPI users] mpi job is blocked
>> To: Open MPI Users <
>> users_at_[hidden]
>> >
>> Message-ID:
>> <
>> CAKbzMGfL0tXDYU82HksoHrwh34CbpwbKmrKwC5DcDBT7A7wTxw_at_[hidden]
>> >
>> Content-Type: text/plain; charset=ISO-8859-1
>>
>> Hi Richard
>>
>> When a collective call hangs, this usually means that one (or more)
>> processes did not reach this command.
>> Are you sure that all processes reach the allreduce statement?
>>
>> If something like this happens to me, i insert print statements just
>> before the MPI-call so i can see which processes made
>> it to this point and which ones did not.
>>
>> Hope this helps a bit
>> Jody
>>
>> On Tue, Sep 25, 2012 at 8:20 AM, Richard <
>> codemonkee_at_[hidden]
>> > wrote:
>> > I have 3 computers with the same Linux system. I have setup the mpi cluster
>> > based on ssh connection.
>> > I have tested a very simple mpi program, it works on the cluster.
>> >
>> > To make my story clear, I name the three computer as A, B and C.
>> >
>> > 1) If I run the job with 2 processes on A and B, it works.
>> > 2) if I run the job with 3 processes on A, B and C, it is blocked.
>> > 3) if I run the job with 2 processes on A and C, it works.
>> > 4) If I run the job with all the 3 processes on A, it works.
>> >
>> > Using gdb I found the line at which it is blocked, it is here
>> >
>> > #7 0x00002ad8a283043e in PMPI_Allreduce (sendbuf=0x7fff09c7c578,
>> > recvbuf=0x7fff09c7c570, count=1, datatype=0x627180, op=0x627780,
>> > comm=0x627380)
>> > at pallreduce.c:105
>> > 105 err = comm->c_coll.coll_allreduce(sendbuf, recvbuf, count,
>> >
>> > It seems that there is a communication problem between some computers. But
>> > the above series of test cannot tell me what
>> > exactly it is. Can anyone help me? thanks.
>> >
>> > Richard
>> >
>> >
>> >
>> >
>> > _______________________________________________
>> > users mailing list
>> >
>> users_at_[hidden]
>>
>> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
>>
>>
>>
>>
>>
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>
>
>--
>Jeff Squyres
>jsquyres_at_[hidden]
>For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
>
>
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