SCENE May 1991

Welcome to the NSCEE

May 1 marks the beginning of the eleventh month of successful operation of the Center. Over 150 users now make use of the Cray Y-MP 2/216 supercomputer, the SUN 4/490 front-end computer, the various SUN SPARCstations and the Silicon Graphics 4D workstation supported by the Center.

The NSCEE was established with $10,000,000 in Congressional funding to provide the computing resource to the State of Nevada for nuclear waste management studies and for use by the University. Current studies on the Cray, conducted by the faculty of the University of Nevada System, include geohydrology, fluid transients, structural analysis, modeling of viscous fluid flows, quantum mechanics, and astrophysics. In each bimonthly issue if this newsletter, we will highlight the work of selected scientists who are employing the NSCEE to further their work. In this issues, the work of Dr. Brikowski of the UNS Desert Research Institute, Dr. Ching Chen of the Mathematics Department at UNLV, James Ventresca, a graduate student in Mechanical Engineering at UNLV, and Dr. Bernard Zygleman of the UNLV Physics Department are discussed. We hope that these articles will give insight into the techniques employed by researchers to use the supercomputing facilities to augment their studies.

Dr. David McNelis, Associate VP for Research, UNLV (left)
and Dr. WIlliam Culbreth, Acting Director, NSCEE (right).

Location

The NSCEE is located on the third floor of the Thomas T. Beam Engineering Complex on the 335-acre campus of the University of Nevada, Las Vegas. UNLV is a doctoral-granting public university with over 18,000 students, serving the State of Nevada. Located in the center if metropolitan Las Vegas with its approximate population of 850,000, the campus is within 2 miles of McCarran International Airport.

NSCEE Affiliates Program

The Center has recently begun a Supercomputing Affiliates Program to provide supercomputing to universities and other entities that lack such resources. To participate in the program, contact the Office of Research at UNLV at (702) 597-4240. Affiliate institutions are asked to identify a contact person that will serve as the institution's source for information on the NSCEE. The contact will receive training in the use of the Cray Y-MP at UNLV, maintain local documentation on the system, and assist in the education of users. The NSCEE provides a grant of a block of computing time annually to its affiliates. Current university affiliates include the Desert Research Institute and the University of Nevada, Reno.

The NSCEE and an Environmental/Energy Initiative

UNLV's National Supercomputing Center for Energy and the Environment (NSCEE) will provide a unique capability to the recently created Energy and Environment research Institute. The Institute is being designed to investigate energy technology, energy alternatives, and the environmental consequences of the various energy options.

A basic goal of the institute will be to promote the development of strong interdisciplinary energy and environmental research programs so that the technology needed to evaluate and implement the various energy alternatives is available. The Institute will emphasize interdisciplinary activities that integrate energy-related/ environmental science and engineering socioeconomics, science/ public policy and ethics, and the regulatory/ legal framework. In addition, a focus will be on the development of the consortia with other universities and public or private research institutions with specific expertise in new/ alternative energy technologies.

An Executive Board, made up of senior representatives from the University, Industry, EPA, DOE and the National Laboratories will provide oversight of the Institute's strategies, plans, and progress. An Advisory Board, which will work with the Institute's management, will provide information, identification of key external linkages and will promote relationships. Finally, the Institute will plan to avail itself of the uncommon advantages and research opportunities provided by the Nevada Test Site, now designated a National Environmental Research Park.

The NSCEE will provide an exceptional capability to UNLV for global-climate change and ground-water investigators in their modeling efforts. It will also serve to link UNLV investigators with others of similar research interests from all over the United States and, in fact, the world.

Scene: The Newsletter Name

One January afternoon, when the first NSCEE bimonthly newsletter was almost finished, I said, "Let's call this something besides 'newsletter.'"

Well, a group of us took the N-S-C-E-E letters and threw them in the air, and they fell to the table: e-n-s-e-c, and then s-n-e-e-c, s-c-e-e-n, n-e-e-c-s, c-e-e-n-s, e-c-e-n-s and then someone yelled out SCENE! The director said yeah, ok, and the editor enthusiastically agreed! We checked the dictionary to make sure it meant what we thought it meant, and we found a *college dictionary defines scene as:

1. The place where some action or event occurs (NSCEE action scene!)

   It also says:

2. Any view or picture. (we have both)
3. An incident or situation in real life (yes, definitely)
4. (no comment)
5. A division of a play, novel, etc. that represents a single episode (How Shakespeare phrased it was more meaningful!)
6. The place in which the action of a story, drama, or dramatic episode is supposed to occur. (It does everyday)
7. Scenery (def. 2) (we have).

Computer Benchmarks

Users who intend to port software to the NSCEE Cray are often interested in the increase in speed of the Cray over their own computers. J. Dongarra* of Argonne National Laboratory has compiled a list of performance times based on the solution of a system of linear equations with LINPACK in full precision using all Fortran code. The NSCEE Cray Y-MP was not tested, however the figures for the Cray Y-MP using only two processors should give an idea of its speed relative to some other machines. Please note that only a fraction of the total number of tested machines in the report are listed below.

1 MFLOP = 1 million floating point operations per second* - Dongara, Jack J., "Performance of Various Computers using Standard Linear Equations Software in a Fortran Environment," Technical Memorandum No. 23, June 4, 1989, Argonne National Laboratory.

Computer Names

In order to be accessible through the Internet, each NSCEE computer is assigned a name. The names of the 17 counties in the State of Nevada were chosen as the basis for the names. The Cray Y-MP 2/216 resides in Clark County and borrows its name. The other workstations and computers at the center were named from the remaining counties in alphabetical order.

March SCENE Corrections

In Vol. 1 No. 1, page 6 (that should have been called page 7): The Cray Y-MP Software Available should read:

Product	Version
CC	PCC 5.03
SCC	Standard C2.0

And on page 6 (called page 7), IP address for the Cray Y-MP 2/216 is 131.216.42.2.

Research Reports

Quantum Mechanical Investigations of Atomic Collision Processes

At the atomic scale, the behavior of matter as governed by the laws of quantum mechanics. Much of modern technology, such as the laser, the transistor and other devices exist because of the peculiar way that matter behaves at the atomic, or quantum level.

In the quantum description, a physical system is characterized by a probability amplitude, or a wavefunction. The wavefunction is a solution to the Schrodinger equation, named after Erwin Schrodinger who first wrote this equation down more than sixty years ago. A knowledge of it is equivalent to full knowledge, in the quantum mechanical sense, of the corresponding physical system. A major goal of theoretical atomic physics is to find accurate solutions of the Schrodinger equation for aggregates of atoms, molecules and other atomic particles. Except for a few isolated cases, the Schrodinger equation describing atomic and molecular systems is sufficiently complex so that analytical solutions are not available. In this case, one must rely on numerical methods to solve the equation.

The collision of two atoms, or ions, is a particularly important process, and is relevant to many energy-related technologies. There are several scenarios that can occur during the collision of two atoms and/ or ions. First, the two collision partners can collide elastically, without affecting their internal energy states.

In a more complicated scenario, the atoms exchange energy or even other particles. Such events are called inelastic collisions. Inelastic processes may also be accompanied by the emission of photons. Because of the prodigious number crunching capabilities of supercomputers, it is now possible to obtain accurate solutions to the Schrodinger equation for many of the collision scenarios outlined above. One feature that makes supercomputers such a powerful tool is the vector architecture of the processor. This architecture is ideally suited for algorithms with a degree of parallelism. In the theoretical treatment of atomic collisions, a mathematical procedure called the partial wave decomposition is often employed.

In this method, the Schrodinger equation is expressed as a set of simpler, uncoupled differential equations. Unfortunately, this set is often quite large, sometimes on the order of thousands, rendering the problem almost intractable on ordinary computers. Because the partial wave equations are decoupled, or independent, one can exploit the vector capabilities of the Cray Y-MP machine in the calculation.

Figure: Spectrum of photons emitted during
collision of helium ions and hydrogen nuclei.

The figure illustrates the spectrum of photons emitted when a positively charged helium ion collides with a neutral hydrogen atom. In this collision, an electron is exchanged and photons are emitted.

This spectrum was obtained by solving the Schrodinger equation on a Cray X-MP supercomputer, and is currently being developed on UNLV's Cray Y-MP.

It is well known that finite fields have been used effectively in many applications. Some of these applications include algebraic coding theory, finite geometrics, block designs, Hadamard matrices, design of experiments, linear modular systems, difference sets, shift register sequences, cryptography for the secure transmissions of information and the generation of psuedorandom numbers. In many of these applications, permutation polynomials play an essential role.

If f(x) is a polynomial of degree n over the finite field Fq of order q = p where q = p is a prime and n >= 1, does the associated polynomial function f: c -> f(C) from Fq into Fq permute the elements of Fq, i.e., is f a 1-1 map of Fq onto itself? If f is a permutation of Fq then the polynomial f(x) is called a permutation polynomial of Fq. Very few good algorithms exist to test whether a given polynomial is a permutation polynomial.

As indicated in [2] very little is known concerning permutation polynomials and in fact [1] provides a description of nine open problems concerning permutation polynomials over finite fields. Problem 9 discusses the Carlitz conjecture from 1966 concerning permutative of even a degree over fields of odd order. This conjecture remains open and so we plan to focus our attention on permutatitve of small degree. All permutatives of degrees 2, 4,and 6 are known and so we will begin by considering permutations of degree 8. The objective of my resent research will attempt by computer to determine all permutations of degree 8 over field of small order q, since the determination of permutation polynomials is rather complicated. As the Carlitz conjecture suggests that for large q in no permutation of degree 8, we hope to be able to determine all permutations of degree 8.

We have achieved some exciting results of testing permutation polynomials of degree 8 with order up to q=37 by using the Cray supercomputer at UNLV. It took approximately 24 CPU hours on the Cray on the case of degree 8 with q-37. The necessary machine time will grow exponentially as the degree increases, which we attempt to reach 10 and 12 if feasible by using Cray. We also, by Cray supercomputers, test the reliability from recent conjecture that generalizes the Carlitz conjecture.

This conjecture involves value sets, and conjecture that if q > 2k(2k - 2) there is no polynomial of degree 2k whose value set has more than q - [(q - 1)/2k] elements.

There are several purposes in this research. The first purpose is to give efficient, stable, and accurate algorithms for testing whether a given polynomial is permutation polynomial. Secondly, we will show these algorithms lead to numerical results for the theory of permutation polynomials. Finally, a software based on our algorithms is anticipated.

Among a variety of applications of permutation polynomials, cryptography is the foremost significant area being investigated worldwide. We hope this project will generate a substantial amount of continuing interest from both finite field researchers and cryptographists to integrate the Cray supercomputer in their research.

References

• [1] R. Lidl and G.L. Mullen, "When does a polynomial over a finite field permute the elements of the filed," Amer. Math. Mon., 95 (1988), 243-246
• [2] W.S. Chou, J. Gomez-Calderan, and G.L. Mullen, "Value sets of Dickenson polynomials over finite fields," J. Numb. Theory, 30(1988), 334-344.

Computational Fluid Dynamics - Viscous Slot-Jet

Jets caused by a fluid flow have several military and industrial applications. They are used in deep hole drilling, cutting tools, jet pumps, cleaning tools and flow mixers such as fuel injectors.

In a fuel injector, for example, it is desirable to control the distribution of the fuel mixture. Through proper analysis of the jet, it can be possible to design the injector to control the flow parameters that would increase the efficiency of the system.

Fluid jets emanating from the exhaust ports can have effects on the environment such as thermal or salinity fluctuations. For a smokestack exhausting into the environment, the dispersion of pollutants and thermal energy can be predicted and controlled through accurate modeling.

Military interests in the study of jets include the defense against targeting of the thermal signatures produced by submarines, tanks, ships, and aircraft.

For this analysis, a finite difference approximation of the vorticity form of the Navier-Stokes equations was used to model a slot-jet issuing into a cross-flow. The result of these equations gives the vorticity, velocity and value of the stream function at a particular point.

In order for the results to approach the analytical solution and for the equations to remain stable, the space and time increments must be made very small. As a result, the size of the matrix that must be solved becomes enormous and the computing time needed to advance a reasonable amount of time steps often makes it impossible to run on most computers.

The typical size of a matrix used for this analysis ranged from 400x400 to 1000x1000. The time steps ranged from 1 to .001 microseconds and a x and y increments ranged from 10 to 100 microns. From the results to this date, flows were modeled at Reynolds numbers up to 7000.

Seen in the figures are plots of streamlines and lines of constant vorticity in a slot-jet issuing into a cross-flowing fluid at various time steps and flow parameters (Reynolds numbers). The cross-flow moves from right to left in the figure and the jet enters from the vertical channel. The flow enters the bottom of the jet nozzle with an assumed uniform velocity distribution. Areas of constant vorticity are shown in the other plot with the highest values of vorticity closer to the surface. The figure shows the build up of vorticity pockets near the exit of the jet.

Topical Reports

Computer Communications Speeds

It is well understood in the computer realm that no matter how much computing power is available, users will require more. The same holds true for communication speeds. Users working through VT-100 terminals, for example, were satisfied with a 9600 baud rate for communication to their central mainframe computer. These text-based terminals could present information on the screen at a rate that exceeded the user's ability to read. Current workstations work with graphical information and the need for high-speed communication has increased dramatically. A screen of information on a text terminal represented only 80x25 or 2 kilobytes of information. A 1024x1024 pixel graphics image with 8-bit planes for color requires a whopping 8.3 megabytes of information. The table to the right represents some common communication speeds with the time required to transmit one screen of high-resolution graphics data.

The Internet currently connects together major computer sites around the world at T1 speeds. The NSF is making an effort to improve these connections to T3. Ethernet is very popular for connecting workstations to host computers at the departmental level. FDDI and HIPPI are high-speed standards that are used for graphics framebuffers and the interconnection of main frame computers.

How fast is fast enough? As the communication speed increases, users learn to exploit the available bandwidth to better complete their jobs. A user that is connected to a Cray supercomputer via a low speed network may never learn to use the windowing systems or available graphics packages due to the lengthy time that it takes to download images.

[This article appeared in the monthly WCCS Newsletter]

We're going to take a brief look at TCP/IP, a popular suite of communication programs for UNIX systems. In addition to the batch job submittal capability available on the NSCEE front-end system, many users will have the capability of communicating directly with the Y-MP via some combination of local- and wide-area networks. TCP/IP which runs on a number of platforms from micros to mainframes, makes this possible by adhering to standard protocols. "TCP" stands for Transmission Control Protocol: "IP" stands for Internet Protocol. Each refers to a set of guidelines established by the Defense Advanced Research Projects Agency (DARPA) for communications among multiple machines. While the scope if the two are wide-ranging, the most common TCP/IP applications are remote login and file transfer.

Before proceeding with our discussion of the application, we should probably introduce some terms. For our purposes, the word network will be used to refer to the physical cabling used between the machines in the question, along with any communications hardware that may be necessary to support data transfer. A host is any computer that is connected to the network and is capable of supporting user sessions. In typical fashion, the host that the user logs directly into (e.g., a workstation or PC) is referred to as the local host. Any other machine upon which subsequent sessions are initiated is called a remote host or a foreign host. Every host on a network that supports IP traffic is assigned a unique numerical network address, as well as a hostname. For example, the host upon which this article is being prepared is known as 'godel', and has a network address of 129.228.2.20. Either may be specified when referencing this particular host.

The two most popular methods of logging into a remote machine such as the Cray are telnet and rlogin. Both are supported under UNICOS.

In the examples that follow, it is assumed that the user is seated at a UNIX workstation. The system prompt for the local workstation is local % (so as to differentiate it from the Y-MP, whose prompt reflects its name on the network: clark $).

In the first example, the user creates an interactive session on the Y-MP using the telnet command. Notice that the user is prompted for a username and password. Upon logout, the connection is closed and the user is returned to the local host.

local % telnet clark

Trying...

Connected to clark
Escape character is '^]'
Cray UNICOS (clark) (ttyp000)

Login: nsceeuseracctname
Password:
Last successful login was: Sun Oct 7 20:10:48

clark $ logout

Connection closed by foreign host
local %

An alternative to "telnet" is the rlogin" command, which assumes that the user wishes to login to the remote host with the same user name as is currently being used on the local host, unless specified otherwise. Notice that while the user is still required to supply a password, there is no prompt for the username.

local % rlogin clark
Password:
Last successful login was: Mon Oct 8 09:41:35 from godel

clark $ logout

Connection closed.
local %

Connecting through Internet

The NSCEE computers are connected to the nationwide Internet. A T1 connection to the San Diego Supercomputer Center provides nationwide communication with computers at major universities at 1.54 million bits per second. The NSCEE computers may be accessed through any machine or terminal-sever connected to the Internet. To access the NSCEE, key:

telnet (host and domain name) or telnet (IP address)
or:
rlogin (host and domain name) or rlogin (IP address)

In our last issue, we described how to connect to the NSCEE computers to the Internet using a modem from 'anywhere.'

Once connected to a NSCEE computer, log into one of the network machines. These, and their IP addresses, are listed above.

For example, if you choose to log into "esmeralda", the following describes a terminal session. You already keyed: telnet esmeralda.nye.nscee.edu

esmeralda %    (waiting for your UNIX command)

esmeralda % ls	lists the files in your current working directory.
esmeralda % ls t*	lists all files that START with t.
esmeralda % ls *8	lists all files that END with 8.
esmeralda % ! l	! followed by a character, will redo the command line that starts with the character. (In this case, it would redo ls *8 again.)
esmeralda % !!	redo the last command line.
esmeralda % cp file1 file2	copies file1 to a file called file 2.
esmeralda % more file1	view file1 on the screen: shows screenful, and then press the spacebar to see the next screen.
esmeralda % lpr file 1	sends a copy of file1 to the printer located in TBE A307.
esmeralda % man passwd	begins displaying the manual pages for the UNIX command 'passwd.' This can be done for most UNIX commands. Key 'q' or (CTRL-c) to stop long man listings.
esmeralda % cat filename	lists the complete contents of file filename, on the screen.

For Additional Internet Information

For users with INTERNET access, additional information can be obtained by anonymous FTP. Key the following:

ftp nye.nscee.edu

Contact the receptionist for the application form and availability. The NSCEE does allow commercial use of the center's computers. Contact the Director's Office for information on rate structure and software licensing policies.

UNLV NSCEE Director	Dr. William Culbreth	(702) 793-3426
NSCEE Receptionist	Paige Zielinski	(702) 597-4153
NSCEE User Services	Gail Whitten	(702) 597-4151
NSCEE Systems-Software Analyst	Michael Ekedahl	(702) 597-4150

To Subscribe

To subscribe to, or make comments about SCENE, the NSCEE's bimonthly newsletter, call User Services or send an email to scene@nye.nscee.edu.

Work performed under the auspices of the University of Nevada, Las Vegas and Westinghouse Electric Corporation under contract.

@Copyright 1991, University of Nevada System, Board of Regents. All Rights Reserved.

The University of Nevada, Las Vegas and Westinghouse Electric Corporation are Equal Opportunity, Affirmative Action Institutions.

Notice

This document was prepared as an account of work sponsored by the University of Nevada, Las Vegas and Westinghouse Electric Corporation. Neither Westinghouse nor the University of Nevada, Las Vegas nor any of their employees, makes any warranty, expressed or implied, or assumes and legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product or process disclosed or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the University of Nevada or Westinghouse. The views and opinions of authors expressed herein do not necessarily state or reflect those of the University of Nevada or Westinghouse, and shall not be used for advertising or product endorsement purposes.

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