Newsgroups: comp.parallel.mpi
From: llewins@msmail4.hac.com (Lloyd J Lewins)
Subject: Re: is synchronous and ready mode necessarily non-buffered?
Organization: Hughes Aerospace Electronics Co.
Date: Fri, 15 Dec 1995 10:02:46 -0800
Message-ID: <llewins-1512951002460001@x-147-16-95-58.es.hac.com>

In article <4anfg9$jn7@knot.queensu.ca>, chang@mjs1.Phy.QueensU.CA wrote:

> Synchronous, ready and buffered mode are all listed as communication
> mode, does this means that Synchronous, ready mode are absolutely
> non-buffered? 

NO.

> The standard is not very clear, it says for synchronous
> mode "the send will complete successfully only if a message receive is
> posted, and the receive operation has started to receive the message
> sent by the synchronous send". This doesn't indicate the completing of send
> means the completing of sending data.

Completion of a synchronous send implies two things:
1) A matching receive has been matched with the send.
2) The message has been copied out of the sending buffer.

It doesn't guarantee that the send it totally complete. E.g., the data may have
been buffered in a system buffer, and may be in transit.

> If synchronous send is non-buffered, the completing of send should means
> completing of sending data;

True, but the choice of whether to buffer or not is an implementation detail.

> if synchronous send is buffered, the completing 
> of send would not mean the completing of sending data.

Again true.

--------------------------------------------------------------------------
Lloyd J Lewins                                  Mail Stop: RE/R1/B507
Hughes Aerospace and Electronics Co.            P.O. Box 92426
                                                Los Angeles, CA 90009-2426
Email: llewins@msmail4.hac.com                  USA
Tel: 1 (310) 334-1145
Any opinions are not neccessarily mine, let alone my employers!!

