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Subject: Re: [OMPI users] Sending relatively large messages with high frequency
From: Amr Hassan (amr.abdelaziz_at_[hidden])
Date: 2010-02-25 03:56:25

Thanks alot for your reply,

I'm using blocking Send and Receive. All the clients are sending data and
the server is receive the messages from the clients with MPI_ANY_SOURCE as
the sender. Do you think there is a race condition near this pattern?

I searched a lot and used totalview but I couldn't detect such case. I
really appreciate if you send me a link or give an example of a possible
race condition in that scenario .

Also, when I partition the message into smaller parts (send in sequence -
all the other clients wait until the send finish) it works fine. is that
exclude the race condition?


>>We've seen similar things in our code. In our case it is probably due to a

>>race condition. Try running the segv'ing process in a debugger, and it
>>likely show you a bug in your code

>>On Feb 24, 2010 9:36 PM, "Amr Hassan " <amr.abdelaziz_at_[hidden]>

>>Hi All,

>>I'm facing a strange problem with OpenMPI.

>>I'm developing an application which is required to send a message from
>>client (1 MB each) to a server node for around 10 times per second (it's a

>>distributed render application and I'm trying to reach a higher frame rate

>>). The problem is that OpenMPI crash in that case and only works if I
>>partition this messages into a set of 20 k sub-messages with a sleep
>>each one of them for around 1 to 10 ms!! This solution is very expensive
>>term of time needed to send the data. Is there any other solutions?

>>The error i got now is:
>>Signal: Segmentation fault (11)
>>Signal code: Address not mapped (1)
>>Failing at address: xxxxxxxxxxxxx

>>The OS is Linux CentOS. I'm using the latest version of OpenMPI.

>>I appreciate any help regarding that.