NA Digest Sunday, September 24, 1989 Volume 89 : Issue 37

Today's Editor: Cleve Moler

Today's Topics:


From: Stephen Boyd <>
Date: Sat, 16 Sep 1989 9:26:20 PDT
Subject: Checking Positive Matrices

Does anyone know of an algorithm for determining whether a matrix is P
or P0, that is NOT combinatoric in the size of the matrix? (a matrix
is P if the determinants of all principal submatrices are positive).
I am not interested in algorithms that work for some matrices (eg
symmetric (!!), or less trivially, matrices with negative offdiagonal
elements); the algorithm must work for general matrices.

Stephen Boyd


From: Martin Berzins <>
Date: Mon, 18 Sep 89 09:37:04 EDT
Subject: Address Change for Martin Berzins

Having finished my sabbatical at RPI,
from 24th September my new email address
will be
Martin Berzins.


From: Masaaki Shimasaki <>
Date: Tue, 19 Sep 89 14:11:56 JST
Subject: Address Change of Masaaki Shimasaki

Please change the E-mail address of Simasaki at Data Processing
Center, Kyoto University to

Thank you.


From: Per Christian Hansen <>
Date: Wed, 20 Sep 89 14:07:18 -0100
Subject: Algorithms for Radon Transforms


Does anybody on the na-net have good numerical algorithms
for computing the Radon transform, and for performing the
inverse Radon transformation?

Since this is a very general problem, let me add that I'm
particularly interested in algorithms for use in seismics.

I'm fully aware that the inverse Radon transform is an ill-
posed problem and, preferably, should be treated with this
aspect in mind. However, I do not know the degree of ill-
posedness of the problem, i.e. the decay rate of the singu-
lar values of the Radon integral operator.

Any hints, comments or other advice is welcome.

Per Christian Hansen
UNI-C (the Danish University Computing Center)
Building 305
Technical University of Denmark
DK-2800 Lyngby

email: na.phansen @


From: Herman te Riele <>
Date: Thu, 21 Sep 89 16:56:06 +0200
Subject: CWI-Symposia on Parallel Scientific Computing



in collaboration with TUD, UvA and IMACS

In collaboration with TUD (Technical University Delft), UvA (University of
Amsterdam) and IMACS (International Association for Mathematics and
Computers in Simulation), CWI will organise five one-day Symposia on
Parallel Scientific Computing. Dates are: 2 Febr., 6 April, 8 June,
7 Sept. and 2 Nov. 1990. Place is CWI Amsterdam, The Netherlands.

Attention will focus on new developments in numerical algorithms for
parallel computing systems, on software tools for parallel computing
(including libraries) and on applications in science and technology
(e.g., fluid dynamics, mechanics, chemistry).

Depending on possible external funding, a number of leading experts
in these fields will be invited to speak.

The organising committee consists of Prof.dr. Th.J. Dekker (UvA), H.J.J. te Riele (CWI) and Prof.dr. H.A. van der Vorst (TUD and CWI).
Abstracts of possible contributions to the first three meetings (2 Febr.,
6 April and 8 June 1990) are solicited now.
The deadline for submission of abstracts is Nov. 1, 1989.
Notification of acceptance will be sent by Jan. 1, 1990.

A special issue of the IMACS Journal "Applied Numerical Mathematics"
will be devoted to the proceedings of the symposia. Contributions will be
subject to the usual refereeing process of IMACS.

Please send for electronic application form.

(On behalf of)
the organising committee,

Herman J.J. te Riele
Centre for Mathematics and
Computer Science (CWI)
Kruislaan 413
1098 SJ Amsterdam
The Netherlands


From: Thomas Seidman <>
Date: 21 Sep 89 13:30:00 EDT
Subject: Positions at University of Maryland Baltimore County


The Department of Mathematics and Statistics at the University of
Maryland Baltimore County has been authorized to recruit for three positions
for the Fall of 1990. At least one of these will be at a senior level; at
least one will be in Statistics.

The Department has strengths in control theory and optimization, in
ordinary and partial differential equations and mathematical modelling, in
numerical analysis and scientific computing, and in probability and statistics.
It seeks strong applicants in these or related areas.

Interested candidates should send a curriculum vitae, a list of
publications, and three letters of reference to:
James M. Greenberg, Chairman
Department of Mathematics and Statistics
University of Maryland Baltimore County
Baltimore, MD 21228
Applicants will be considered until three suitable candidates have been found.



From: Robert Voigt <>
Date: Fri, 22 Sep 89 08:22:09 EDT
Subject: David Kamowitz

On September 16 David Kamowitz died of complications associated with a long
bout with cancer.

David came to ICASE from Wisconsin three years ago. He struggled with his
disease for over two years, admonishing his doctors to keep trying up until
the very end. He was one of the most courageous people I have known and I
consider myself fortunate to have been associated with him.

Bob Voigt


From: Ake Bjorck <>
Date: Fri, 22 Sep 89 14:50:43 +0200
Subject: Householder Symposium XI


The Householder Symposium XI on numerical algebra will be held
during the week of June 18--22, 1990 at Tylosand, Halmstad on the west
coast of Sweden. This meeting is the eleventh in a series, previously called
the Gatlinburg Symposia. It has been agreed to rename all subsequent
Gatlinburg Symposia to honor Alston S. Householder, one of the pioneers
in Numerical Linear Algebra and organizer of the first four
Gatlinburg meetings. The meeting is an international conference of experts
in the field of Numerical Algebra. The format of the meeting is a sequence of
invited papers during the day and special workshops organized by the
participants in the evening. There is no formal program, but traditionally
a few topics are emphasized. For this meeting they will be large scale
nonsymmetric linear algebra problems, least squares, and matrix inertia
and stability.

The meeting is being organized by the Householder committee, in cooperation
with the SIAM Activity Group on Linear Algebra.
Chairman of the committee for this meeting, and in charge of the
local organization is Ake Bjorck of Linkoping University, Sweden.

The traditional format of the Householder Symposia requires that
the attendance is limited. The organizing committee invites all qualified
persons to apply to attend. The application should consist of a vita and an
extended abstract (about two pages) of a paper you would present if invited to
speak. The latter will be used by the committee in planning the program.
Material should be sent before November 1, 1989 to

Ake Bjorck
Department of Mathematics
Linkoping University
S-581 83 Linkoping, SWEDEN

The Gatlinburg Conferences are international workshops on the theoretical
and numerical aspects of linear algebra and its application. They were started
by Alston S. Householder and initially held at Gatlinburg, Tennessee,
approximately once every three years. After the first four meetings it was
decided to hold the conferences under the same name at varying locations.
The custom has become to have every third meeting in Europe. For a review
of the earlier meetings see an article in SIAM Review [1977]. A complete
list of previous meetings is given below:

I. April 1961 Gatlinburg, Tennessee A. S. Householder
II. October 1963 Gatlinburg, Tennessee F. Olver
III. April 1964 Gatlinburg, Tennessee A. S. Householder
IV. April 1969 Gatlinburg, Tennessee A. S. Householder
V. April 1972 Los Alamos, New Mexico A. S. Householder
VI. December 1974 Hopfen am See, Germany F. L. Bauer
VII. December 1977 Asilomar, California G.H. Golub
VIII.July 1981 Oxford, England J.H. Wilkinson
IX. July 1984 Waterloo, Canada J.A. George
X. October 1987 Fairfield Glades, Tennessee G.W. Stewart

The Gatlinburg meetings brings together theoreticians, numerical analysts,
and application researchers from all over the world. During the day, there
are lectures (no parallel sessions) by people judged to be doing especially
interesting work in their areas. In the evenings, the participants organize
special sessions or minisymposia over areas of current interest.
Traditionally the interaction is very open and intense, and many workers
attribute some of their best results to ideas that originated at a
Gatlinburg conference. The meetings have played an important part
in the evolution of scientific computing, and it is hard to overstate the role
these conferences have played in fostering and sustaining international
cooperation in numerical algebra.

Attendance at the Gatlinburg Conferences is by invitation, and procedures
have been devised that hopefully insure that a fair selection is made.
It is anticipated that 100-120 people will be invited to the present meeting.
Even though several open meetings are held in linear algebra, these conferences
are unique in that here the best people in the field from all countries have
a chance to get together and interact informally.

Hotel Tylosand is situated by the sea on the west coast of Sweden. The hotel
has recently been renovated and modernized and is a conference center of the
best international class. The location is removed from any big cities and
offers excellent opportunities for physical exercise.
Room and buffet breakfast is approximately $65 single and $60 double occupancy.
It is hoped that the meeting can be run with the same modest registration
fee $50 as the previous meeting at Fairfield Glades.


From: Rich Sincovec <>
Date: Fri, 22 Sep 89 14:55:07 PDT
Subject: Positions at RIACS




The Research Institute for Advanced Computer Science (RIACS) is an
institute of the Universities Space Research Association operating under
a cooperative agreement with the NASA Ames Research Center and is devoted
to the conduct of research in computer science aimed at the challenging
problems faced by NASA. Current research programs include development,
integration, and evaluation of advanced computer science technologies
supporting the use of multiple resources connected by networks, the study
of advanced numerical algorithms and parallel computing architectures,
and memory models for robotics and other applications.


The RIACS computing facility serves our staff of approximately forty
individuals and consists of the following equipment:

Sequent Balance 21000s, Encore Multimax, Ardent, Stellar, NeXT,
various X Stations, network access to NASA Ames computers including
Cray Y_MP, Cray 2 and CM-2, 26 Sun 3 workstations with 3 dedicated
file servers running Sun OS 4.0, uucp server, internet gateway to

The RIACS facility is principally based on UNIX and X Windows.

* Systems programming and maintenance on the computing facility.
* Systems administration for the Sun network.
* Applications programming supporting research projects
in scientific computing with an emphasis on numerical algorithms
for parallel computer architectures.
* Frequent interaction with RIACS and NASA scientists.

* M.S. in Computer Science or equivalent experience
* Two or more years experience working with UNIX, including
experience with the kernel and net-working.
* Ability to work well with people and excellent communications skills
* U.S. Citizenship or Permanent Residence.

Send your resume to:
Richard Sincovec
RIACS - Research Institute for Advanced Computer Science
Mail Stop 230-5
NASA Ames Research Center
Moffett Field, CA 94035
Office Phone: (415)694-4342 FAX Number: (415)961-8467


End of NA Digest