[mpich-discuss] messages queue

[Jarosław Bułat]

Changing MPI_Send to MPI_Isend + MPI_Wait does not change anything. The
system is to complex to send a small test program, however, I'm working
on it - I'm trying to extract a smal fragment of it.

I've tested a few configuration with the following results:

mpich2-1.0.7:
1) ch3:nemesis
2) ch3:sock
3) ch3:shm

First configuration crash after 67 (every time) unprocessed messages,
second configuration freeze after 2000-4000 unprocessed messages and
third after 18 (every time) unprocessed messages. 
Freeze means I wasn't be able to send another message, however I was
able to receive and process queued messages and thus shorten queue and
send another message which is expected behaviour.

The length of one message described above is 28 Bytes, however before
this test (second phase) several other (longer, up to 1.2 MBytes)
messages have been successfully send, received and processed (first
phase).

configuration of MPI:
mpich2version
MPICH2 Version:        1.0.7
MPICH2 Release date:    Unknown, built on Fri Jul  4 15:06:00 CEST 2008
MPICH2 Device:        ch3:shm
MPICH2 configure:     --enable-sharedlibs=gcc -prefix=/usr/ --enable-cxx
--with-device=ch3:shm
MPICH2 CC:     gcc  -O2
MPICH2 CXX:     g++  -O2
MPICH2 F77:     g77  -O2

Everything is working on the Ubuntu 8.04 with CoreDuo processor (2core).
MPICH as well as program was compile by means of gcc 4.2.3 (Ubuntu
4.2.3-2-ubuntu7).

Any ideas? how can I test it more precisely? 


Regards,
Jarek !


On Thu, 2008-07-03 at 14:51 -0500, Rajeev Thakur wrote:
> A queue of 100 messages of 100 bytes is not too big. What happens if you
> replace MPI_Send with MPI_Isend? Can you send us a small test program?
> 
> Rajeev
>  
> 
> > -----Original Message-----
> > From: owner-mpich-discuss at mcs.anl.gov 
> > [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Jaroslaw Bulat
> > Sent: Thursday, July 03, 2008 7:57 AM
> > To: mpich2
> > Subject: [mpich-discuss] messages queue
> > 
> > Hi All!
> > 
> > I found the following problem using MPICH2 (1.0.6 and 1.0.7 with sock
> > and nemesis channel). There are 5 unique process which interchange
> > messages by means of MPI_Send() and MPI_Irecv() + MPI_Waitany() or
> > MPI_Testany(). Since the MPI_Send() doesn't wait until 
> > receiver receive
> > message and process it, it is possible to see a queue of messages
> > waiting for processing at the receiver.  In such a situation my sender
> > proces is crashing during calling MPI_Send() function.  Queue of
> > unprocessed messages is of the length of ~100 messages of the 
> > length 100
> > Bytes each.
> > I cannot use MPI_Ssend() which resolve this problem because 
> > in this way
> > my system is less responsive.
> > 
> > How can I control length of queue? 
> > Is it possible to allocate more memory for internal MPI buffer? 
> > 
> > 
> > Regards,
> > Jarek!
> > 
> > 
> > 
> >