[MPICH] MPICH2 Thread-safety

[Sylvain Jeaugey]

Seems to work much, much, much better.
Thanks !

Sylvain

On Fri, 9 Jun 2006, Rajeev Thakur wrote:

> What happens if you just configure with --enable-threads?
>
> Rajeev
>
>> -----Original Message-----
>> From: Sylvain Jeaugey [mailto:sylvain.jeaugey at bull.net]
>> Sent: Friday, June 09, 2006 9:10 AM
>> To: Rajeev Thakur
>> Cc: 'Sylvain Jeaugey'; mpich-discuss at mcs.anl.gov
>> Subject: RE: [MPICH] MPICH2 Thread-safety
>>
>> On Fri, 9 Jun 2006, Rajeev Thakur wrote:
>>
>>> Sylvain,
>>>        A lot of things are happening thread-safety-wise in
>> MPICH2. 1.0.4
>>> will have much better support.
>> Good to hear !
>>> Nonetheless, the paragraph you quote will
>>> work in 1.0.3 as well because the lock is released
>> somewhere inside the
>>> progress engine before a receive blocks. (It's not obvious
>> from looking at
>>> the code for MPI_Recv.)
>> Ok. Good.
>>
>>> What exactly doesn't work for you? We have fixed a
>>> couple of bugs that were found.
>> It doesn't compile with
>> ./configure --enable-threads=multiple:global_mutex
>> typing 'make' after configure gives :
>> In file included from ../../../../include/mpiimpl.h:83,
>>                   from sock.c:9:
>> ../../../../include/mpiimplthread.h:10:49: syntax error ':'
>> without preceding '?'
>> ... and a lot of other errors after that.
>>
>>> Another fix that is coming is that you won't need to build
>> MPICH2 separately
>>> to get a thread safe version. Support for thread safety
>> will be there by
>>> default and will be enabled when the user selects it with
>> MPI_Init_thread.
>>> If the user doesn't call MPI_Init_thread, the code will not
>> use any thread
>>> locks, so there is no penalty.
>> That's a very, very good thing ! I'm eager to have this new version !
>>
>> Thanks for your help,
>>
>> Sylvain
>>
>>>> -----Original Message-----
>>>> From: owner-mpich-discuss at mcs.anl.gov
>>>> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of
>> Sylvain Jeaugey
>>>> Sent: Friday, June 09, 2006 7:04 AM
>>>> To: mpich-discuss at mcs.anl.gov
>>>> Subject: [MPICH] MPICH2 Thread-safety
>>>>
>>>> Hi all,
>>>>
>>>> After some tries, it looks like MPICH2 is still a little far
>>>> from being
>>>> thread-safe.
>>>>
>>>> Nothing seems to be currently done in this direction, so I'm
>>>> posting here
>>>> to know what I could do to improve this.
>>>>
>>>> The only thread policy is "global_mutex", which -in my view-
>>>> contradicts
>>>> Section 8.7.1 of the standard :
>>>>
>>>> "Example Process 0 consists of two threads. The first thread
>>>> executes a
>>>> blocking send call MPI_Send(buff1, count, type, 0, 0, comm),
>>>> whereas the
>>>> second thread executes a blocking receive call
>> MPI_Recv(buff2, count,
>>>> type, 0, 0, comm, &status). I.e., the first thread sends a
>>>> message that is
>>>> received by the second thread. This communication should
>>>> always succeed."
>>>>
>>>> There is a lot of code for "thread-safety". Still, I can't
>>>> get something
>>>> working.
>>>> Is there a chance that things will be better in 1.0.4 ? Where
>>>> should I
>>>> begin if I want to improve things (and not destroy what's
>> already be
>>>> done) ?
>>>>
>>>> Thanks in advance,
>>>>
>>>> Sylvain
>>>>
>>>>
>>>
>>>
>>
>>
>
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