[mpich-discuss] discuss Digest, Vol 8, Issue 39

Mon Jun 24 16:30:57 CDT 2013

N threads calling MPI_Barrier corresponds to N different, unrelated
barriers.  A thread calling MPI_Barrier will only synchronize with
other processes, not any other threads.

MPI_Barrier only acts between processes.  It has no effect on threads.
 Just use comm=MPI_COMM_SELF and think about the behavior of
MPI_Barrier.  That is the one-process limit of the multithreaded
problem.

Jeff

On Mon, Jun 24, 2013 at 4:22 PM, Antonio J. Peña <apenya at mcs.anl.gov> wrote:
>
> Hi Jeff,
>
> Please correct me where I'm wrong: if only one thread calls MPI_Barrier, that
> one will get locked while others will go ahead. On the other hand, if every
> thread calls MPI_Barrier, all will get locked in that call until the barrier
> completes. That doesn't mean this will be a replacement for thread-wise
> synchronization mechanisms, but will be effective for all of them waiting for
> the barrier.
>
>   Antonio
>
>
> On Monday, June 24, 2013 04:14:20 PM Jeff Hammond wrote:
>> MPI_Barrier will not sync threads.  If N threads call MPI_Barrier, you will
>> get at best the same result as if you call MPI_Barrier N times from the
>> main thread.
>>
>> If you want to sync threads, you need to sync them with the appropriate
>> thread API.  OpenMP and Pthreads both have barrier calls.  If you want a
>> fast Pthread barrier, you should not use pthread_barrier though.  The
>> Internet has details.
>>
>> Jeff
>>
>> ----- Original Message -----
>> From: "Antonio J. Peña" <apenya at mcs.anl.gov>
>> To: discuss at mpich.org
>> Sent: Monday, June 24, 2013 3:49:08 PM
>> Subject: Re: [mpich-discuss] discuss Digest, Vol 8, Issue 39
>>
>>
>>
>>
>>
>>
>> Sufeng,
>>
>>
>>
>> I'd say you're OK syncing your threads by all of them calling MPI_Barrier,
>> as it's a thread-safe function.
>>
>>
>>
>> Antonio
>>
>>
>>
>>
>>
>> On Monday, June 24, 2013 11:41:44 AM Sufeng Niu wrote:
>>
>>
>> Hi, Antonio
>>
>>
>>
>> Thanks a lot! Now I make sense. Let's say if I am running MPI and
>> multithreads program. If I called MPI_Barrier in each threads
>>
>>
>> what gonna happen? Will threads be synced by MPI_Barrier? or I should use
>> thread level sync?
>>
>>
>>
>> Thank you!
>>
>>
>> Sufeng
>>
>>
>>
>>
>>
>>
>> On Sun, Jun 23, 2013 at 6:54 PM, < discuss-request at mpich.org > wrote:
>>
>>
>> Send discuss mailing list submissions to
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>> When replying, please edit your Subject line so it is more specific
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>>
>>
>> Today's Topics:
>>
>> 1. Re: Error with MPI_Spawn (Jeff Hammond)
>> 2. Re: discuss Digest, Vol 8, Issue 37 (Antonio J. Pe?a)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sun, 23 Jun 2013 17:03:09 -0500
>> From: Jeff Hammond < jeff.science at gmail.com >
>> To: " discuss at mpich.org " < discuss at mpich.org >
>> Subject: Re: [mpich-discuss] Error with MPI_Spawn
>> Message-ID: <-1578386667793986954 at unknownmsgid>
>> Content-Type: text/plain; charset=ISO-8859-1
>>
>> This is the wrong way to use PETSc and to parallelize a code with a
>> parallel library in general.
>>
>> Write the PETSc user list and they will explain to you how to
>> parallelize your code properly with PETSc.
>>
>> Jeff
>>
>> Sent from my iPhone
>>
>> On Jun 23, 2013, at 4:59 PM, Nitel Muhtaroglu < muhtaroglu.n at gmail.com >
> wrote:
>> > Hello,
>> >
>> > I am trying to integrate PETSc library to a serial program. The idea is
>> > that the serial program creates a linear equation system and then calls
>> > PETSc solver by MPI_Spawn and then solves this system in parallel. But
>> > when I execute MPI_Spawn the following error message occurs and the
>> > solver is not called. I couldn't find a solution to this error. Does
>> > anyone have an idea about it?
>> >
>> > Kind Regards,
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Sun, 23 Jun 2013 18:54:38 -0500
>> From: Antonio J. Pe?a < apenya at mcs.anl.gov >
>> To: discuss at mpich.org
>> Subject: Re: [mpich-discuss] discuss Digest, Vol 8, Issue 37
>> Message-ID: <8872211.IGCl89YM8r at localhost.localdomain>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>>
>> Sufeng,
>>
>> The correct way is to use the MPI_Init_thread function with
>> MPI_THREAD_MULTIPLE. This will tell the MPI implementation to be thread
>> safe. It supports OpenMP and Posix Threads (OpenMP primitives in most
>> systems are likely to be implemented on top of PThreads).
>>
>> Antonio
>>
>>
>> On Sunday, June 23, 2013 11:13:31 AM Sufeng Niu wrote:
>>
>>
>> Hi, Antonio
>>
>>
>> Thanks a lot for your reply, I just figure out that is the firewall issue.
>> after I set the firewall. it works now. Thanks again.
>>
>>
>> But I still got a few questions on MPI and multithreads mixed programming.
>> Currently, I try to run each process on each server, and each process
>> using thread pool to run multiple threads (pthread lib). I am not sure
>> whether it is the correct way or not. I wrote it as:
>>
>>
>> MPI_Init()
>> ....
>> ...
>> /* create thread pool and initial */
>> ......
>> /* fetch job into thread pool */
>> ......
>>
>>
>> MPI_Finalize();
>>
>>
>> When I check the book and notes, I found people use
>>
>>
>> MPI_Init_thread() with MPI_THREAD_MULTIPLE
>>
>>
>> but the some docs said it supported OpenMP, is that possible to use it
>> with pthread library?
>> I am new guy to this hybrid programming. I am not sure which is the proper
>> way to do it. Any suggestions are appreciate. Thank you!
>>
>>
>> Sufeng
>>
>>
>>
>>
>> On Sat, Jun 22, 2013 at 12:12 PM, < discuss-request at mpich.org [1]> wrote:
>>
>>
>> Send discuss mailing list submissions to discuss at mpich.org [2]
>> https://lists.mpich.org/mailman/listinfo/discuss[3]
>> discuss-request at mpich.org [1]
>> discuss-owner at mpich.org [4]
>> sniu at hawk.iit.edu [5]>To: discuss at mpich.org [2]
>> CAFNNHkwpqdGfZXctL0Uz3hpeL25mZZMtB93qGXjc_+tjnV4csA at mail.gmail.c
>> om[6]>Content-Type: text/plain; charset="iso-8859-1"
>>
>> Hi,
>>
>> Sorry to bother you guys on this stupid question. last time I re-install
>> OSfor all blades to keep them the same version. after I mount, set
>> keylessssh, the terimnal gives the error below:
>>
>> [ proxy:0:1 at iocfccd3.aps.anl.gov [7]]
>> HYDU_sock_connect(./utils/sock/sock.c:174): unable to connect from
>> " iocfccd3.aps.anl.gov [8]" to" iocfccd1.aps.anl.gov [9]" (No route to host)
>> [ proxy:0:1 at iocfccd3.aps.anl.gov [7]] main (./pm/pmiserv/pmip.c:189):
>> unable toconnect to server iocfccd1.aps.anl.gov [9] at port 38242 (check
>> for firewalls!)
>>
>> I can ssh from iocfccd1 to iocfccd3 without password. Should I shut downall
>> firewalls on each server? I cannot find out where is the problem. Thankyou
>>
>> --Best Regards,Sufeng NiuECASP lab, ECE department, Illinois Institute of
>> TechnologyTel: 312-731-7219[10]
>> http://lists.mpich.org/pipermail/discuss/attachments/20130621/5503b1bc/a
>> ttachment-0001.html[11] >
>>
>> ------------------------------
>>
>> Message: 2Date: Fri, 21 Jun 2013 10:58:26 -0500From: Antonio J. Pe?a
>> < apenya at mcs.anl.gov [12]>To: discuss at mpich.org [2]
>> iocfccd1.aps.anl.gov [9]" from iocfccd3?[1]
>>
>> Antonio
>>
>>
>> On Friday, June 21, 2013 10:51:50 AM Sufeng Niu wrote:
>>
>>
>> Hi,
>>
>>
>> Sorry to bother you guys on this stupid question. last time I re-install OS
>> forall blades to keep them the same version. after I mount, set keyless
>> ssh,the terimnal gives the error below:
>>
>>
>> proxy:0:1 at iocfccd3.aps.anl.gov [7][2]]
>> HYDU_sock_connect(./utils/sock/sock.c:174): unable to connect from
>> " iocfccd3.aps.anl.gov [8][3]"to " iocfccd1.aps.anl.gov [9][1]" (No route to
>> host)[ proxy:0:1 at iocfccd3.aps.anl.gov [7][2]] main
>> (./pm/pmiserv/pmip.c:189):unable to connect to server
>> iocfccd1.aps.anl.gov [9][1] at port 38242 (checkfor firewalls!)
>>
>>
>>
>> I can ssh from iocfccd1 to iocfccd3 without password. Should I shut downall
>> firewalls on each server? I cannot find out where is the problem. Thankyou
>>
>>
>>
>>
>> -- Best Regards,Sufeng NiuECASP lab, ECE department, Illinois Institute of
>> TechnologyTel: 312-731-7219[4]
>>
>>
>> --------[1] _ http://iocfccd1.aps.anl.gov_
>> proxy%3A0%3A1 at iocfccd3.aps.anl.gov [13]
>> http://iocfccd3.aps.anl.gov [8]
>> 312-731-7219[10]
>> http://lists.mpich.org/pipermail/discuss/attachments/20130621/01b37902/
>> attachment-0001.html[14] >
>>
>> ------------------------------
>>
>> Message: 3Date: Sat, 22 Jun 2013 12:49:10 -0400From: Jiri Simsa
>> < jsimsa at cs.cmu.edu [15]>To: discuss at mpich.org [2]
>> CAHs9ut-_6W6SOHTJ_rD+shQ76bo4cTCuFVAy1f9x-
>> J0gioakHg at mail.gmail.com [16]>Content-Type: text/plain;
>> charset="iso-8859-1"
>>
>> Hi,
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>>
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>> End of discuss Digest, Vol 8, Issue 39
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-- 
Jeff Hammond
jeff.science at gmail.com