**Today's Topics:**

- Who is Working on Moving Boundary Problems?
- Representation in Terms of Vertices
- Stability of Block Toeplitz algorithms
- Knuth's Spectral Test
- Loss of Significance Register
- Optimal Coefficient Lookup
- Special Issue of LAA on Image Reconstruction
- GAMM Meeting in Karlsruhe
- Conference Announcement
- IFIP WG 2.5 Conference Scheduled in 1991

From: George Wilson <wilson@msr.EPM.ORNL.GOV>

Date: Tue, 1 Nov 88 11:58:55 EST

I have been asked by a student from Argentina if I knew of anyone in the

Boston, MA, area who does mathematical and computational work on moving

and/or free boundary problems (examples include: porous media problems,

dam problems, contact problems, phase change processes ...). She is

considering a post doc position at MIT working with an engineering faculty

member, but she is interested in also interacting with a more mathematically

oriented person. Are any of you interested in such problems? Do you know

someone in the (greater) Boston area who is? Incidentally, the student is

bright, energetic and speaks excellent English. George Wilson

bitnet: dgw@ornlstc arpanet: wilson@msr.epm.ornl.gov

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

From: Michael Todd <miketodd@gvax.cs.cornell.edu>

Date: Tue, 1 Nov 88 20:44:35 EST

Last month there were a couple of questions about representing a point in a

polyhedron in terms of its vertices. An easy solution solves at most n+1 LP's.

Let the polyhedron be given by Ax >= b, and assume it is bounded (otherwise,

the claimed result is not necessarily true). Let x-bar be the given point,

and assume it satisfies the subsystem Bx >= c with equality. Now solve the

LP of minimizing d.x subject to Ax >= b, Bx = c, to get a vertex x-hat. Find

the point on the line through x-hat and x-bar that is on the boundary of the

face Ax >= b, Bx = c, say x-tilde. Now x-tilde satisfies at least one more

inequality at equality. If it is a vertex, you're done. Otherwise, use an

inductive argument to express x-tilde as a convex combination of vertices,

whence such a representation for x-bar can easily be found.

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

From: Kletsky Jeff <KLETSKY@GIZMO.SRI.COM>

Date: Thu 3 Nov 88 09:40:18-GMT

We have been using the Block Toeplitz solver TGSLD from the Argonne

Toeplitz Package for some time now on a class of problems containing

128x128 blocks with a block size of 16x16. As our blocks are symmetric

indefinite, the LINPACK routines DSIFA and DSISL have been substituted

for the general routines DGEFA and DGESL.

Recently, we were tasked by an "informed" source to demonstrate

that double precision (VAX Fortran) was sufficient. (He could only

obtain results using quad precision with his own implementation of his

personal pet algorithm.) A quick edit of the Argonne and LINPACK codes

yielded quad precision versions. When we compared results on a case

with moderate conditioning, the solution vectors agreed exactly, save

for the least significant bit in one element.

However, when we examined closely related problem that was poorly

conditioned, although the solution obtained from the double precision

version of the code seemed to be stable and reasonable, the quad precision

version became unstable and yielded unreasonable results, beginning at the

38th block/iteration.

It seems strange to me that improving the numerical precision should

reduce the stability of such an algorithm. Any advice or experience that

others might have on this would be greatly appreciated.

Thanks,

Jeff Kletsky

kletsky@gizmo.sri.com

(415) 859-3948

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From: Ajay <dukempd!ajay@cs.duke.edu>

Date: 2 Nov 88 16:30:21 GMT

I was wondering if anyone had a program (machine readable or

otherwise) in FORTRAN or C for Knuth's Spectral Test, as

described in his book "The Art of Computer Programming"

for testing Random Number Generators. I would be extremely

grateful if someone could help me out. If you can, please

send me e-mail(ajay@dukempd.cs.duke.edu).

Thanks. Ajay

Ajay 1-919-684-8236

Duke University Dept. of Physics ajay@dukempd.uucp

Durham, N.C. 27706 mcnc!duke!dukempd!ajay

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

From: Paul L Schauble <portal!cup.portal.com!PLS@uunet.uu.net>

Date: 5 Nov 88 03:51:25 GMT

Looking through some old paperwork brought back to mind a very old machine I

used to work on. This machine contained an interesting feature. It has a

register that stored the maximum postnormalizing shift performed. This was

updated for each floating point add or subtract. There was an instruction to

store and clear this register.

This seems like a useful feature. You could run a data item through an

algorithm, then store this register and see what precision was actually

maintained through the algorithm.

My question is that I haven't seen this feature or any equivalent in any

modern hardware. Why? Has experience shown it to be useless? Is there some

non-obvious problem with it?

-- Paul Schauble

The Portal System

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

From: Peter Mikes <under!pom@mordor.s1.gov>

Date: 2 Nov 88 18:38:22 GMT

I would like references and or pointers to any work which is addressing

the question described below as OCL (it already may have a name -

I just made the OCL up, not knowing any better)

It is a mundane problem, but it is quite ubiquious and general -

so it may deserve some name and optimalization study:

The OCL problem: I am writing an PDE solver ( PDE = Partial Differential

Equation) in which the coefficients c depend in various ways on the both

dependent and independent variables. Since these functions tend to be

evaluated over and over again, in the course of the solution and iterations,

they are often pre-calculated and stored in the look-up tables.

That is one extreme solution - taking lot of memory and memory lookup time.

On the other extreme, one may store nothing, but original few coefficients

and recalculate the value of the coefficient each time when it is neeeded.

The optimum seems to be somewhere in between - for example, one can

break the coeficient domain in the regions - and each region aproximate with

sufficient precision the coeficient i = c[i] with some simple function, e.g

with linear or polynomial or rational function with parameters a[...],

e.g.: c[i] = SUM.over.j a[i,j,l] *X[l]^j

where j (the powers ) range from j.min to j.max.

For example, one would have D(T) = a0 + a2 /T for a temperature

dependent Diffusion coeficient - and in this case j.min= -1,j.max=0 , etc

OCL problems asks:

what is the optimal j.min and j.max, given ..

well given all that affects the optimum : relative cost of CPUtime and

memory, memory latency (or latencies), number N of evaluations needed, etc

Extended OCL question deals with the fact that coefficients may

not be exactly known (the often are not) and so we a)only want to have

them aproximated with certain precision and b) we may want to know the

sensitivity of the solution (without repeating the whole solution with

the second set of values). Iin this case we have a range of coefficients

c[i] +/- delta c[i] and want to obtain the 'class of the solutions' which

corresponds to this range. The question again is : what is the numerically

'best' way for representing the functions c[i]( X[l] ), where X represents

physical space and fields (e.g. temperature) variables, so that MINIMAL TIME T

is spent in multiple (=N.times) evaluation of these functions?

The time T(N) represents essentially the CPU time - but we may include

the memory cost by adding a memory latency time T.mem as =cost of retrieving a

precalculated value...

So, in summary, the OCL problem asks:

Find J.min,Jmax (for given N) which will minimize T[J.min, J.max]

needed to aproximate (within epsilon) class of functions c[i](X[l]),

which are continuous (except at small number of the 'phase transition'

boundaries) and otherwise 'reasonable'.

Since N >>>1, the cost of computing the aproximation (preparation

of look-ups) is neglected and does not enter the T. the Time T however

includes the time Tc 'cost of checking whether we are crossing the

region boundary' N-times - to keep the number of regions reasonably small.

Any suggestions, references, pointers will be appreciated

and those e-mailed will be summarized.

Peter O. Mikes

Supercomputer R&D Project, LLNL

pom@under.s1.gov.

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

From: Hans Schneider <hans@pade.math.wisc.edu>

Date: Wed, 2 Nov 88 19:09:41 cst

LINEAR ALGEBRA AND ITS APPLICATIONS

Special Issue on

LINEAR ALGEBRA IN IMAGE RECONSTRUCTION FROM PROJECTIONS

Reminder

This special special issue of LAA is still open for submissions. It

is intended to include papers in linear algebra and optimization

theory which are related to computerized tomography and other image

reconstruction techniques for medical and other purposes. See LAA,

Vol.99 (1988), for the full announcement of the issue and see

Censor's article in SIAM News, Vol.21 (#4, July 1988) pp.14-15, for

a general description of the area. The special editors wish to

encourage you to submit your paper for consideration.

Yair Censor, Haifa, Israel.

(e-mail: rsma403@haifauvm.bitnet).

Gabor T. Herman, Philadelphia, PA, USA

(e-mail: herman@cis.upenn.edu).

Tommy Elfving, Linkoping, Sweden

(e-mail: t-elfving%linnea.liu.se@uunet.uu.net).

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

From: Goetz Alefeld <AE02%DKAUNI48.BITNET@Forsythe.Stanford.EDU>

Date: 11/03/88 14:00:50 CET

The Gesellschaft fuer Angewandte Mathematik und Mechanik

invites you to attend its Annual Scientific Conference

at Karlsruhe University

from March 28 to March 31, 1989

The regular General Assembly of GAMM will be held on Thursday,

March 30, 1989, at 12:00 a.m. in Gerthsen-Hoersaal.

Plenary Lectures

E.Hoerbst, Siemens AG Muenchen

Methoden des Halbleiterentwurfs - eine Aufgabe fuer den Mathematiker ?

G.C.Hsiao, University of Delaware, Newark

The Coupling of Boundary Element and Finite Element Methods

E.Krause, TH Aachen

Anwendungen numerischer Integrationsverfahren in der Stroemungsmechanik

P.C.Mueller, Universitaet Wuppertal

Parameteridentifikation in mechanischen Systemen

F.Obermeier, Max-Planck-Institut Goettingen

Ausbreitung schwacher Stosswellen - Stossfokussierung und

Stossreflexion

M.L.Overton, Courant Institute New York

Numerical Methods for Inverse and Extremal Eigenvalue Problems

S.B.Savage, McGill University Montreal

Dynamics of Avalanches of Granular Materials

J.W.Schmidt, TU Dresden

Monotonie und Einschliessung in der Numerik

H.R.Schwarz, Universitaet Zu

The Deutsche Gesellschaft fuer Luft und Raumfahrt, and the Gesellschaft

fuer Angewandte Mathematik und Mechanik invite you to the

32nd Ludwig Prandtl Memorial Lecture

Professor Dr.K.Gersten, Universitaet Bochum, will lecture on

"The Significance of Prandtl's Boundary Layer Theory after 85 years"

(in German).

Public Lecture

A public lecture titled

"High Tech = Math Tech"

will be held by Professor Dr.H.Neunzert, Universitaet Kaiserslautern.

This lecture will be given in Gerthsen-Hoersaal.

Additional Information

If you are interested in attending the conference send your mailing

address to the Organizing Committee (na.alefeld@na-net.stanford.edu)

We will send you the registration form and the necessary information.

G. Alefeld, Local Organizer

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

From: Claudio Canuto <MAT7%ITOPOLI.BITNET@Forsythe.Stanford.EDU>

Date: Sat, 5 Nov 88 11:34 N

I C O S A H O M '8 9

INTERNATIONAL CONFERENCE ON SPECTRAL AND HIGH ORDER METHODS

FOR PARTIAL DIFFERENTIAL EQUATIONS

Villa Olmo (Lake of Como, Italy) - June 26-29, 1989

TOPICS : Theory, algorithms, applications of Spectral Methods, h-p version

of Finite Element Methods, high-order Finite Difference Methods,

etc. Applications to Fluid Mechanics, Continuum Mechanics, Turbulence,

Combustion and Engineering Sciences in general.

The Conference will try to answer the following question: When,

why and to what extent it is preferable to use high-order methods

in the numerical approximation of differential problems.

SCIENTIFIC COMMITTEE : I.Babuska, C.Canuto, M.Deville, D.Gottlieb,

M.Y.Hussaini, Y.Maday, R.Peyret, A.Quarteroni.

LOCAL ORGANIZING COMMITTE : C.Canuto and A.Quarteroni

FORMAT : The Conference will host 45-minute invited lectures (approximately

16), and 20-minute contributed talks (up to about 30).

INVITED LECTURERS : I.Babuska (University of Maryland), M.Deville (Universite'

Catholique de Louvain), D.Gottlieb (Brown University), M.Y.Hussaini

(ICASE), N.F.Knight (NASA Langley), Y.Maday (Universite' de Paris VI), S.A.

Orszag (Princeton University), S.Osher (UCLA), A.Patera (MIT), R.Peyret

(Universite' de Nice), P.Sguazzero (IBM-ECSEC, Rome), B.A.Szabo (Washington

University), E.Tadmor (Tel Aviv University), L.N.Trefethen (MIT), T.A.Zang

(NASA Langley).

PROCEEDINGS : The proceedings of the Conference will be published by Elsevier-

North-Holland (Amsterdam).

LOCATION : The Conference center is in Villa Olmo, a beautiful neo-classic

building of the 18th century facing the lake, located in Como, a restful town

surrounded by green hills and mountains, close to Milan and the Swiss border.

Como is served by the European railways and motorways system, and by nearby

Milan and Zurich airports. Participants will find the right atmosphere of

calm and peacefulness necessary to ensure successful working.

REGISTRATION : People who wish to attend the Conference are requested to send

----------- IMMEDIATELY -------------

an e-mail message at the following address:

mat7@itopoli.bitnet

(att/n : Claudio Canuto)

in which they say whether they will just participate or also submit the

abstract of a contributed talk (see below).

The registration fee is Lit. 250,000 (Italian Lira) if paid before April 30,

1989, or Lit. 300,000 if paid later on. The fee include the scientific material

as well as daily buffet during the Conference. Graduate students will pay

half the fee.

CALL FOR PAPERS : Researchers in the areas of interest of the Conference are

invited to contribute by submitting an abstract of a possible talk. The

abstracts, not exceeding two typewritten pages, shoud be sent as soon as

possible to the following address:

The Organizers of ICOSAHOM'89

IAN-CNR, Corso Carlo Alberto,5

27100 PAVIA, Italy

Tel.: (39)-382-303740

e-Mail: cqa04@ipvian.bitnet

or : mat7@itopoli.bitnet

All the abstracts will be examined by the Scientific Committee by January

31, 1989, and authors will be promptly informed about acceptance of their

talk. Contributed papers, not exceeding 8 typewritten pages, should be sent

to the address above by April 30, 1989, and should conform to the typing

instructions which will accompany the acceptance notices.

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

From: Bo Einarsson <B_EINARS%SELIUC51.BITNET@Forsythe.Stanford.EDU>

Date: Mon, 31 Oct 88 14:21 N

INTERNATIONAL FEDERATION FOR INFORMATION PROCESSING

Working Group 2.5 on Numerical Software

Bo Einarsson, 31 October 1988

IFIP TC 2 WORKING CONFERENCE

PROGRAMMING ENVIRONMENTS FOR

HIGH LEVEL SCIENTIFIC PROBLEM SOLVING

First Announcement and Call for Interest

A working conference on Programming Environments for High Level

Scientific Problem Solving, will be arranged 23 - 27 September 1991 in

the Karlsruhe area, Federal Republic of Germany. This will be the

sixth working conference organized by the IFIP Working Group on

Numerical Software (WG 2.5) on behalf of the IFIP Technical Committee

on Programming (TC 2).

This letter is an invitation to you from the preliminary programme

committee to contribute your ideas for this conference. At present we

are very interested in suggestions regarding the scope of the

conference, who to invite to attend and who to invite as speakers, and

on which specific topics, and whether you are interested in

participating.

The conference will concentrate on the construction of high-level

scientific problem solving systems. We are particularly interested in

DESIGN OF USER INTERFACES

Techniques for problem description

Presentation and interpretation of results

Graphical, symbolic and numerical techniques

Multiple modes of I/O (digital, analog, graphical, audio,...)

TECHNIQUES FOR PROBLEM SOLVING

Dynamic selection of algorithms

Use of knowledge bases about problem solving

Integration of numerical, symbolic and graphical methods

User interaction and feedback

Accuracy control and estimation, self-validating systems

IMPLEMENTATION ISSUES

Mixed language programming

Declarative, dynamic and visual programming systems

Integration of libraries and multiple problem solving systems

Tools for integration and portability

Efficient utilization of computing resources, parallel and

distributed architectures, graphics engines

The programme committee will encourage speakers to put together

dynamic (live) talks, using the facilities being described. It is

also intended to complement the presentations with a hardware and

software exhibit, and to produce the proceedings not only as a book

(published by Elsevier) but perhaps also as a video cassette or disk.

The discussions will be recorded in the proceedings. All papers will

be refereed.

Previous working conferences arranged by WG 2.5 have focused on

performance evaluation of numerical software, numerical computation

and programming languages, software for partial differential

equations, problem solving environments, and aspects of computation on

asynchronous parallel processors. The number of participants will be

limited, in order to preserve informality and allow substantial time

for interaction.

The preliminary programme committee consists of Michel Bercovier

(Jerusalem, Israel), Jacques Calmet (Karlsruhe, Germany), Ifay Chang

(IBM, New York), Bo Einarsson (Linkoping, Sweden), Stuart Feldman

(Bell, New Jersey), Brian Ford (NAG, United Kingdom), Lloyd Fosdick

(Boulder, Colorado), Patrick Gaffney (IBM, Norway), Morven Gentleman

(Ottawa, Canada), Elias Houstis (Patras, Greece), Ulrich Kulisch

(Karlsruhe, Germany), John Rice (West Lafayette, Indiana) and Mladen

Vouk (Raleigh, North Carolina).

For further information you are invited to contact the programme

committee co-chairmen

Bo Einarsson, Mathematics Department, University of Linkoping,

S-581 83 Linkoping, SWEDEN.

Telephone +46 13 281432 (office) or 151896 (home).

Electronic mail BOGE@SELIUC51.BITNET or b-einarsson@linnea.liu.se

or na.einarsson@na-net.stanford.edu

Lloyd D. Fosdick, Department of Computer Science, Campus Box 430,

University of Colorado, Boulder, Colorado 80309, USA.

Telephone (303) 492 7507 (office) or 444 1065 (home).

Electronic mail lloyd@boulder.colorado.edu or na.fosdick@na-net.stanford.edu

We hope that you will join us in organizing a stimulating and

enjoyable Working Conference on a challenging and new topic.

Sincerely

Bo Einarsson and Lloyd D Fosdick

..............................................................................

Reply form (return to one of the above, either electronically or by

the conventional mail)

Name:

Mailing Address:

Telephone:

Electronic Mail:

Wishes to participate: Yes/No

Wishes to give a talk: Yes/No

Topic:

Wishes to suggest that the following individuals are contacted (please

give full mailing address and/or electronic mail address):

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

End of NA Digest

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