Subject: comms2 and comms3 bugs, mpi release

From: Ron Sercely <[email-masked]>
Date: Mon, 09 Sep 1996 15:39:52 -0500

HP/Convex wants to release lowlevel numbers in two weeks, but we are
trying to
figure out what to do about the bugs we have reported in these codes.

Options are:
Submitting results without these tests
HP/Convex Re-writing the benchmarks to "do the right thing"
other ?

I would appreciate a phone call to discuss these issues.
-- 
Ron Sercely
214.497.4667

HP/CXTC Toolsmith

---

From: Mark Baker <[email-masked]>
Date: Tue, 10 Sep 96 10:10:24

Ron,

Ian Glendenning and I produced the first MPI port of the low-level
codes for Parkbench approximately a year ago. 

Erich Strohmaier (who works for Jack Dongarra at UTK) has been managing
and maintaining all the parkbench codes since then.

I would suggest he reply to you on the subject.

If you do not get a reply I am willing to help.

Regards

Mark

>I would appreciate a phone call to discuss these issues.

-------------------------------------
Dr Mark Baker
DIS, University of Portsmouth, Hants, UK
E-mail: [email-masked]
Date: 10/09/96 - Time: 10:10:24
URL http://www.npac.syr.edu/
-------------------------------------

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From: Vladimir Getov <[email-masked]>
Date: Tue, 10 Sep 96 08:58:36 BST

Hi Ron,

Are you talking about the same or similar bugs as the ones reported for
the comms3 benchmark by Harikumar Sivaraman at the end of June (see the
included message below)?

			-Vladimir Getov

p.s. Apologies if you receive this message more than once - I have 
included [email-masked] on the "To:" line but do not know
the cross membership.
> I would appreciate a phone call to discuss these issues.
____________________________  included message  _______________________
>From [email-masked] Fri Jun 28 15:54:32 1996
From: [email-masked] (Harikumar Sivaraman)
Subject: Bug report on COMMS3.f in PARKBENCH2.0
To: [email-masked], [email-masked]
Date: Fri, 28 Jun 96 9:50:26 CDT
Cc: [email-masked] (Paco Romero)
X-Mailer: ELM [version 2.3 PL11]
Content-Length: 1559
X-Status: 

DISCLAIMER: The contents of this mail are not an official HP position.
	    I do not speak for HP.

The COMMS3 benchmark in PARKBENCH2.0 is in apparent violation of 
the specifications in the MPI standard. The benchmark attempts to do an
MPI_RECV into the same buffer on which it has posted an MPI_ISEND
before it does an MPI_WAIT. The relevant code fragment is as below:

COMMS3  (This code fragments applies in the case of two processors)
------
CALL MPI_ISEND(A, IWORD, MPI_DOUBLE_PRECISION, .....

CALL MPI_RECV(A, IWORD, MPI_DOUBLE_PRECISION, ......

CALL MPI_WAIT(request(NSLAVE), status, ierr)

COMMS3  (Multiple processors)
------

do i = 1, #processors
   CALL MPI_ISEND(A, IWORD, MPI_DOUBLE_PRECISION, .....
enddo

// The MPI_ISEND statements in the loop violate the MPI standard since the buffer "A"
//  is reused inside the loop.

do i = 1, #processors
   CALL MPI_RECV(A, IWORD, MPI_DOUBLE_PRECISION, ......
enddo

do i = 1, #processors
   CALL MPI_WAIT(request(NSLAVE), status, ierr)
enddo

Comments:
---------
The MPI standards (page 40, last but one paragraph) says "the sender should
not access any part of the send buffer after a nonblocking send operation 
is called, until the send completes." Page 41, line 1 of the MPI standards says 
"the functions MPI_WAIT and MPI_TEST are used to complete a nonblocking
communication". Clearly the reuse of buffer "A" in the code fragments
above is in violation of the standard. 

-------
H. Sivaraman                                  (214) 497 - 4374
HP; 3000 Waterview Pk.way
Dallas, TX - 75080

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From: Erich Strohmaier <[email-masked]>
Date: Tue, 10 Sep 1996 08:40:58 -0400

Ron,

We fixed the two bugs you mentioned and we are currently testing the
new codes.  The new version should be out by end of this week.  If you
would like to get it earlier, please let me know.

Best Regards

Erich

===========================================================================
Erich Strohmaier                       email:  [email-masked]
Department of Computer Science         phone:  ++ 1 (423) 974 0293
104 Ayres Hall                         fax  :  ++ 1 (423) 974 8296
Knoxville TN, 37996 - USA              http://www.cs.utk.edu/~erich/