From: Edwin Vollebregt <edwin@pa.twi.tudelft.nl>
Newsgroups: comp.parallel.pvm
Subject: SUNMP: pvmftrecv eating up CPU-cycles
Date: Tue, 15 Dec 1998 18:21:07 +0100
Organization: Delft University of Technology
Message-Id: <36769A83.24424D10@pa.twi.tudelft.nl>
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Hello,

I've been PVM now since a number of years with a lot of pleasure,
but when porting our application to a multi-processor SUN machine
(don't know the exact type from the head, PVM_ARCH=SUNMP) we got
a number of problems.

The application consists of a number of worker processes, finite
difference code, SPMD, working and communicating, and a single
master process for error handling, standard output and so on.

The problem is that the function pvmftrecv in the master is consuming
a lot of cpu-time, which slows down one of the workers considerably,
which in turn kills our so far nice speedup.

Anyone have suggestions/already ran into this problem ?

Using pvm v.3.3.11.  Time-out: 1 sec --> nearly 1 sec cpu-time ??
Time-out: -1sec --> 20% of wall-clock time spent in receiving messages.
pvmfrecv: same problem.

Of course I can build another trecv if I have a means for letting the
master do nothing for T seconds, with T=100*time for probe, with 1%
overhead.  I'm not very familiar with C, so do you know of a good way
to let a process do nothing for T seconds ?

Thanks a lot,
	Edwin Vollebregt