**Today's Topics:**

- NAG Replies to Proskurowski
- Algorithms and Parallel VLSI Workshop
- Address Change for Zlatev
- Where is George Marsaglia
- FFT's for Solving Elliptic Equations

From: Peter Mayes <NAGPJM%vax.oxford.ac.uk@nsfnet-relay.ac.uk>

Date: Mon, 7 Aug 89 17:05 BST

We would like to thank Professor Proskurowski for his comments on the

NAG multigrid routine D03EEF and its documentation.

Firstly a few words on the philosophy behind the example programs to be

found in the NAG Library manual. These programs are really intended to

give a simple example of how to set up a problem, call the routine and

interpret the results. They are not designed to show the full

capabilities of any particular routine, nor are they intended to show

the behaviour of the routine on particularly "difficult" or "special"

examples. In addition, they are not intended to test the implementation

of the underlying numerical algorithm. For this we have a separate set

of "stringent" test programs.

Turning to the particular routine D03EEF, the example chosen has a

quadratic solution, with zero truncation error for central differences.

This has the unintentional advantage that it gives a demonstration of

the correctness of the implementation in this case. In fact, the results

given by Professor Proskurowski are in good agreement with the multigrid

theory. However, the example has the disadvantage that it gives the

wrong impression about what the user is likely to see from his/her own

problem. It would have been better to give as an example a problem for

which second-order differences gave only second-order accuracy.

We are currently in the process of finalising code and documentation for

Mark 14, and we will change the example to treat a less "special" case.

Thank you very much

Peter Mayes, NAG

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From: Harry Nelis <dutentb!harry@dutentb.tudelft.nl>

Date: Wed, 9 Aug 89 14:35:45 met

International Workshop on

Algorithms and Parallel VLSI Architectures

June 10--16, 1990

Les Houches, France

Announcement and Call for Papers

Conference Committee

Ed Deprettere Patrick Dewilde

Dept. of Electrical Engineering Dept. of Electrical Engineering

Delft University of Technology Delft University of Technology

email: ed@dutentb email: dewilde@dutentb

Thomas Kailath Sun-Yuan Kung

Information Systems Laboratory Dept. of Electrical Engineering

Stanford University Princeton University

email: tk@isl.stanford.edu email: kung@princeton.edu

Henk van der Vorst Prabhakar Rao

Dept. of Mathematics Dept. of Electrical Engineering

Delft University of Technology Drexel University

email: numan@dutinfd email: rao@drexel

The workshop will consist of a number of courses and workshops.

The following topics will be covered:

Courses

Schur's Algorithm and its Applications

Array Forms of Fast Signal Processing Algorithms

Architecture Design

Multiscale Signal Processing

Large Scale Modeling

Solving Large Systems of Linear Equations

Workshops

Computer Graphics Modeling with Finite Elements

Signal Estimation Adaptive and Orthogonal Filtering

Video Architectures Architectures for Control and Communications

Microcoded Architectures Systolic Architectures

Artificial Neural Nets Eigenvalues and Singular Values

The courses will be given by eminent lecturers in the field (names will be

announced shortly).

The workshops will consist of plenary talks by invited speakers and poster

sessions.

We plan to have one course and two workshops per day.

Papers are solicited for contributions to the workshops, and will have to be

presented in poster format.

Authors are invited to submit four copies of a 4-page summary of the paper to

the workshop secretariat for review.

Papers will be severely reviewed --- the number of accepted papers is limited.

Authors of accepted papers will be asked to prepare a version for publication.

Authors' Schedule

Submission of 4-page summary: Februari 19, 1990

Notification of Acceptance: March 30, 1990

Workshop Secretariat

Harry Nelis

Dept. of Electrical Engineering

Delft University of Technology

2628 CD Delft, The Netherlands

email: harry@dutentb

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From: Zahari Zlatev <zlatev@uicsrd.csrd.uiuc.edu>

Date: Wed, 9 Aug 89 11:18:20 -0500

My stay at the Center for Supercomputing Research and Development

at the University of Illinois at Urbana-Champaign is finishing

soon. After August 17 I shall be back in Denmark at the old

address:

Air Pollution Laboratory

Danish Agency for Environmental Protection

Risoe National Laboratory

DK-4000 Roskilde, DENMARK

E-mail address: LFLZL@NEUVM1.BITNET

or NA.ZLATEV@NA-NET.STANFORD.EDU

------------------------------

From: Jim Walker <walkerj%wnre.aecl.cdn@relay.ubc.ca>

Date: 10 Aug 89 13:21 -0600

Does anyone have the email address and FAX number for George Marsaglia

(random numbers etc.)

Jim Walker.

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From: John D. McCalpin <mccalpin@nu.cs.fsu.edu>

Date: 11 Aug 89 12:38:35 GMT

I would like to be able to use an FFT-based method for solving a

finite-difference version of a linear, separable elliptic equation

with Neumann boundary conditions. I routinely use this technique to

solve the same problem with periodic boundaries in one or both

directions.

The one unusual aspect of this problem is that the derivative of the

solution is not specified at a grid point, but exactly midway between

two grid points. (This is a natural specification of a derivative for

the finite-difference part of the equation).

It seems that it should be possible to "twiddle" with the transformed

variables to introduce the appropriate phase shift, but I can't figure

out how to do it.

Solutions which are only first-order accurate in space are not

interesting. On the other hand, the value of the derivative at the

boundaries is _almost_ zero, and I may be able to get away with

calling it zero and trying to use a cosine transform -- if I can

figure out how to apply the appropriate phase shift.

Any pointers wil be appreciated!

John D. McCalpin - mccalpin@masig1.ocean.fsu.edu - mccalpin@nu.cs.fsu.edu

mccalpin@delocn.udel.edu

Supercomputer Computations Research Institute

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End of NA Digest

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