You should always assume that MPI_SEND will block. This is the safest
model for MPI applications -- the conditions for which MPI_SEND will
block (or not) are totally dependent upon the MPI implementation and
usually the network that it the message is traversing (e.g., LAM
changes its blocking behavior depending on the RPI used).
So assume that MPI_SEND will block, but don't rely on it for
synchronization. Use MPI_SSEND if you need synchronization.
Hope that helps.
On Feb 11, 2005, at 11:28 AM, Shi Jin wrote:
> Hi, from most MPI books, MPI_Send is said to be
> blocking.
> But I found in the man page of LAM/MPI this is not
> always true:
>
> This function may block until the message is
> received. Whether or not MPI_Send blocks depends on
> factors such as how large the message is, how many
> messages are pending to the specific destination,
> whether LAMD or C2C communication is being used, etc.
>
> Where can I find more information on the exact
> conditions of blocking and nonblocking?
>
> Thanks a lot.
>
> Shi
>
>
>
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--
{+} Jeff Squyres
{+} jsquyres_at_[hidden]
{+} http://www.lam-mpi.org/
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