Pedro -
The configuration parameters are in the device dependent sections, as
the parameter changes based on which device you are using. THe
default device is the usyv shared memory/tcp device, which may not
actually allow you to change the eager limit.
As I mentioned before, this will not solve your problem. LAM will
block MPI_Send calls during resource constrained situations (which are
likely random), regardless of how big you make the eager limit. Your
code is simply incorrect and unsafe, and therefore should be updated
as Davide suggested.
Brian
On Apr 8, 2009, at 3:02 PM, Pedro Petrovitch wrote:
> Hi, first of all thanks for your time and attention.
>
> Could you be a little more specific on which parameter should be set
> or maybe in which section of the document I would find that
> information?
> I've looked for it already and couldn't find it.
>
> Best regards,
> Pedro Petrovitch.
>
> > From: brbarret_at_[hidden]
> > To: lam_at_[hidden]
> > Date: Wed, 8 Apr 2009 13:51:14 -0600
> > Subject: Re: LAM: lam mpi message length without blocking
> >
> > On Apr 7, 2009, at 1:08 AM, Davide Cesari wrote:
> >
> > > Pedro Petrovitch ha scritto:
> > >> I've experienced a lock at my program while using the the pattern
> > >> that guarantees that it won't lock,
> > >> if the send isn't blocking (I use a MPI_Send and then a MPI_Recv
> > >> for both processes). The lock just started to happen
> > >
> > > Well, MPI_Send and MPI_Recv ARE blocking functions, so, if the
> > > communication pattern is such that it may create a deadlock (or as
> > > you say, it will not deadlock only if communication is not
> > > blocking), then you will probably experience locking at a certain
> > > message size.
> >
> > Davide's absolutely correct - MPI_Send may block at any time. With
> > LAM, they may block at any message size (including 0 byte) depending
> > on queue sizes. If your code can't run with all calls to MPI_Send
> > replaced to MPI_Ssend (synchronous send), your code is not correct.
> >
> > >> when the messages being transfered got bigger. I've made some
> > >> research about it and found out that there was
> > >> something called MP_EAGER_LIMIT in IBM's implementation that let
> > >> the user set the size of messages without
> > >> the need of using rendesvouz protocol. Is there something like
> that
> > >> in LAM's implementation?
> > >
> > > I think there is something similar also for LAM, maybe at
> > > compilation time, don't know for sure, but it is not wise to
> rely on
> > > it for avoiding blocking, if you want to guarantee portability and
> > > reliability for your application, you had better use MPI_Isend
> and/
> > > or MPI_Irecv at the cost of a slightly more complex code.
> >
> > The parameter to be set depends on the underlying device, and
> setting
> > it for some devices is not a good idea. Have a look at the LAM/MPI
> > user's guide (http://www.lam-mpi.org/using/docs/) for more
> information.
> >
> > Brian
> >
> >
> > --
> > Brian Barrett
> > LAM/MPI Developer
> > Make today a LAM/MPI day!
> >
> >
> > _______________________________________________
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>
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--
Brian Barrett
LAM/MPI Developer
Make today a LAM/MPI day!
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