krj@na.toronto.edu (Ken Jackson) (01/09/89)
NA Digest Sunday, January 8, 1989 Volume 89 : Issue 1 Today's Editor: Cleve Moler Today's Topics: Complexity of Approximately Solved Problems Numerical Solution of Markov Chains Conference on Numerical Combustion SIAM Student Competition Positions in Supercomputing at NASA Ames Numerical Computation Position at U. Colorado Random Story ------------------------------------------------------- From: Joe Traub <traub@cs.columbia.edu> Date: Tue, 3 Jan 1989 9:26:19 EST Subject: Complexity of Approximately Solved Problems SECOND CALL FOR PAPERS Third Symposium on Complexity of Approximately Solved Problems Computer Science Department Columbia University April 3-5, 1989 PROGRAM COMMITTEE: Kenneth Arrow Department of Economics Stanford University Stanford, California Jerome Feldman International Computer Science Institute 147 Center Street Berkeley, California Richard Karp Computer Science Department University of California at Berkeley Berkeley, California Christos Papadimitriou Computer Science Department University of California at San Diego San Diego, California Steven Smale Mathematics Department University of California at Berkeley Berkeley, California Joseph Traub Computer Science Department Columbia University New York, New York Henryk Wozniakowski Computer Science Department Columbia University New York, New York Donald Ylvisaker Statistics Department University of California at Los Angeles Los Angeles, California PARTIAL LIST OF SPEAKERS PLENARY SPEAKERS: Leon N. Cooper Brown University Steven Smale University of California, Berkeley INVITED SPEAKERS: Adam Bojanczyk Cornell University Terrance Boult Columbia University David Donoho University of California, Berkeley Zvi Galil Columbia University Feng Gao University of British Columbia Ehud Kalai Northwestern University Mark Kon Boston University Marek A. Kowalski University of Warsaw J. Kuczynski University of Warsaw David Lee AT&T Bell Laboratories Leonid Levin Boston University Mario Milanese Politecnico di Torino Erich Novak University of Erlangen Michael Shub IBM, T.J. Watson Research Center K. Sikorski University of Utah Michael Steele Princeton University Aleksei Sukharev Moscow State University John N. Tsitsiklis Massachusetts Institute of Technology Umesh Vazirani University of California, Berkeley Grace Wahba University of Wisconsin Greg Wasilkowski University of Kentucky Arthur Werschulz Columbia University Henryk Wozniakowski Columbia University SOME OF THE TOPICS TO BE ADDRESSED ARE: Average Case Analysis of Algorithms Neural Nets Computational Complexity Optimal Recovery Computer Vision Parallel Computation Connectionist Models Prediction and Estimation Continuous Complexity Random Algorithms Decision Theory Random Complexity Design of Experiment Robotics Distributed Complexity Scientific Computation Information-Based Complexity Seismology Inverse Problems Signal Processing Mathematical Economics CONTRIBUTED PAPERS: All appropriate papers for which abstracts are contributed will be scheduled. Contributed papers will be twenty minutes in length. To contribute a paper send title, author, affiliation, and abstract on a single 8 1/2 by 11 sheet of paper or by electronic mail. The above can be sent by U.S. mail to: J.F. Traub Computer Science Department Columbia University 450 Computer Science Building New York, New York 10027 Electronic Mail: kerny@cs.columbia.edu TITLES AND ABSTRACTS MUST BE RECEIVED BY NO LATER THAN FEBRUARY 1, 1989 PUBLICATION: Invited papers will be published in the Journal of Complexity. REGISTRATION: The symposium will be held in the Kellogg Conference Center, on the fifteenth floor of the International Affairs Building, Columbia University, 118th Street and Amsterdam Avenue. Registration will start at 9:00 a.m. THERE IS NO REGISTRATION CHARGE. FOR FURTHER INFORMATION: The program schedule will be sent electronically about March 1, 1989. If you have any questions, contact Kerny McLaughlin, Computer Science Department, Columbia University, (212) 854-2736. below and return by U.S. Mail to Traub or by electronic mail to kerny@cs.columbia.edu. SYMPOSIUM ON COMPLEXITY OF APPROXIMATELY SOLVED PROBLEMS April 3-5, 1989 Name: Affiliation: Address: [ ] I will attend the Complexity Symposium. [ ] I may attend the Complexity Symposium. [ ] I will contribute a paper. ------------------------------ From: William J. Stewart <billy@ece-csc.ncsu.edu> Date: Wed, 4 Jan 89 09:31:25 EST Subject: Numerical Solution of Markov Chains Call for Papers FIRST INTERNATIONAL WORKSHOP ON THE NUMERICAL SOLUTION OF MARKOV CHAINS North Carolina State University Raleigh, N. Carolina, 27695-8206, USA. January 8-10, 1990 The workshop aims are twofold: To foster cooperation among researchers and practitioners working on diverse aspects of the numerical solution of Markov chains; and to provide an opportunity for researchers to present their latest results. The collection of presentations intends to be an authoritative over- view of the field, including its developments, current status, and projections for future directions. With this in mind, the program will consist of both invited and contributed papers. The workshop proceedings will be published. Workshop Organization: Program Chairman: William J. Stewart, NCSU Local Organizing Comm: C.D. Meyer, NCSU R.J. Plemmons, NCSU K. Trivedi, Duke University S. Stidham, Jr., UNC Speakers Participating in the Workshop: P.J. Courtois Philips Research, Belgium N.M. Van Dijk Vrije Univ., Netherlands G.H. Golub Stanford Univ., USA W.K. Grassmann U. of Saskatchewan, Canada G. Latouche U. Libre de Bruxelles, Belgium D. Mitra AT&T Bell Labs, USA M.F. Neuts U. of Arizona, USA Y. Saad RIACS, USA P. Schweitzer U. of Rochester, N.Y., USA E. Seneta U. of Sydney, Australia G.W. Stewart U. of Maryland, USA Y. Takahashi Tohoku Univ., Japan K. Trivedi Duke Univ., USA List of Topics: Applications Matrix Generation Techniques Stochastic Petri Nets Computation of Stationary Probability Vectors Direct Solution Methods Iterative Solution Methods Recursive Solution Methods (incl. those of Neuts) Domain Decomposition Methods Incomplete Factorizations etc. Computation of Transient Solutions Randomization/Uniformization O.D.E. & P.D.E. Solvers Others Approximations Aggregation/Disaggregation Very Large State Spaces Bounds Markov Reward Models Infinite Markov Chains Sensitivity Analysis Parallel Implementations P.C. Demonstrations IMPORTANT DATES: June 1, 1989 Deadline for paper submission Sept. 1, 1989 Notification of acceptance Oct. 15, 1989 Final versions due Jan. 8-10, 1990 Workshop INSTRUCTIONS: Submit five copies of a full paper to W.J. Stewart by June 1, 1989. Papers should be no more than 20 double-spaced typewritten pages, including tables and figures. All correspondance should be addressed to William J. Stewart Department of Computer Science North Carolina State University Box 8206 Raleigh, N.C. 27695-8206, USA Phone: (919) 737-7824 E-mail: billy@ece-csc.ncsu.edu ------------------------------ From: Ed Block <IEBLOCK@wharton.upenn.edu> Date: Wed, 4 Jan 89 21:23 EST Subject: Conference on Numerical Combustion Dear Colleague: As you may know, INRIA, in association with SIAM, is conducting the Third International Conference on Numerical Combustion. The conference will be held on May 23-26, 1989, in Antibes on the French Riviera. Due to the recent French postal strike, the distribution of the call-for-papers was delayed, especially in the United States. Bernard Larrouturou, the French chair of the conference, has asked me to let you know that the deadline for proposed contributions has been postponed to January 15, 1989. If you are interested in submitting a paper for this conference, it is suggested that you send it now to: Therese Bricheteau INRIA Domaine de Voluceau BP 105 - Roquencourt 78153 Le Chesnay Cedex FRANCE Tel: 33/1/39-63-56-00 Telex: 697033F Other relevant details are: Topics: numerical methods for combustion problems, numerical simulation of combustion phenomena. Full contributions: ten (10) pages maximum. Notification of acceptance: January 31, 1989 I hope we have been in time to give you the opportunity to send your contributions to INRIA. I. Edward Block SIAM January 4, 1989 ------------------------------ From: Ed Block <IEBLOCK@wharton.upenn.edu> Date: Thu, 5 Jan 89 18:40 EST Subject: SIAM Student Competition January 5, 1989 MEMORANDUM TO: STUDENTS AND THEIR ADVISERS Subject: Best Papers Competition The following announcement will appear in the January issue of SIAM News: The student authors of the three best papers in applied and computational mathematics submitted to SIAM will be invited by SIAM to attend its annual meeting in San Diego, July 17-21, 1989. Each winner will receive up to $750 to offset expenses and will be recognized at the meeting. Papers must be singly authored to be eligible for consideration. Winners must present their papers at the meeting to receive the awards. In submitting their work for publication, authors are asked to consider the SIAM journals. To qualify, authors must be students in good standing who have not received their PhDs at the time of the submission. Submissions must be received by SIAM on or before April 1, 1989. Submissions can be sent by regular mail or Fax. Each submission must include (1) an extended abstract (3-4) pages, double-spaced, in English); (2) the signature of the author (on the submission); (3) a statement by the student's faculty adviser (also on the submission) that the paper has been prepared by the author indicated and that the author is a student in good standing; and (4) a short biography of the student. Each submission must also include a letter of recommendation from the student's adviser or department chair. Submissions will be judged on the basis of originality, applicability, and clarity of exposition. The winners will be notified by May 15, 1989. Submissions and questions about this competition should be sent to A. Bogardo, c/o San Diego Competition, SIAM, 1400 Architects Building, Philadelphia, PA 19103-5052. E-mail to siam@wharton.upenn.edu. Fax to (215) 564-4174. Students interested in joining SIAM (only $15 per year) are invited to write to SIAM for membership information. ------------------------------ From: Eugene Miya <eugene@orville.nas.nasa.gov> Date: Thu, 05 Jan 89 18:32:04 PST Subject: Positions in Supercomputing at NASA Ames Supercomputing: No Experience Required A Special Announcement of Opportunity (AO) Numerical Aerodynamic Simulation Systems Division NASA Ames Research Center The Numerical Aerodynamic Simulation (NAS) Systems Division is seeking new, recent, "fresh-out," graduates for challenging positions in large-scale computer systems research, development, and operational support at the NASA Ames Research Center located on Moffett Field, CA [southern-most tip of San Francisco Bay in the Santa Clara Valley]. The NAS Facility houses one of the world's largest and most advanced supercomputer systems, used by a nationwide user community for solving highly complex problems in fluid dynamics, aeronautics, space, and other scientific disciplines. The System includes a CRAY Y-MP*, a CRAY-2, a Thinking Machine's Connection Machine-2, dual Amdahl 5880's, four VAX 11/780s, over 30 Silicon Graphics Iris and SUN workstations interconnected with local area networks ranging in speed 10 to 800 Mhz. The user visible operating system is UNIX with TCP/IP-based networking extensions. Systems research, development, and computational service opportunities exist in the following areas: 1) Supercomputers 2) Mass Storage Systems 3) High Performance Scientific Workstations 4) High Performance Data Networks 5) Long Haul Communications 6) Mini-supercomputers Future developments will involve NeXT machines, Ardent Titan and Stellar graphical superworkstations, and other flavors of state of the art high technology. These positions require at least a Bachelor's degree [or more] in computer science, engineering, or one of the physical sciences. Knowledge of the UNIX operating system and the DoD Internet Protocols is highly desireable. This is an excellent entry opportunity for the young and young-at-heart. NASA (The National Aeronautics and Space Administration) is the Nation's civilian space Agency. The NASA Ames Research Center is an Equal Opportunity Employer. US Citizenship is required. Security clearance is not required. Send resumes to: Mr. Bruce Blaylock Chief, NAS Systems Development Branch M/S 258-5 NASA Ames Research Center Moffett Field, CA 94035 blaylock@prandtl.nas.nasa.gov or ames!prandtl!blaylock TeX and troff okay. *Trademarks: CRAY Y-MP, CRAY-2 are trademarks of Cray Research Inc. Connection Machine-2 is a trademark of Thinking Machines Corp. UNIX is a trademark of AT&T Bell Laboratories. VAX is a trademark of Digital Equipment Corporation. Iris is a trademark of Silicon Graphics Inc. SUN is a trademark of SUN Microsystems Inc. Send specific questions to me. -- Eugene Miya ------------------------------ From: Bobby Schnabel <bobby@boulder.Colorado.EDU> Date: Fri, 6 Jan 89 14:25:01 MST Subject: Numerical Computation Position at U. Colorado UNIVERSITY OF COLORADO DEPARTMENT OF COMPUTER SCIENCE We invite applications for a faculty position in parallel and numerical computation. Preference is at the assistant professor level, but candidates at all levels will be considered. The Department has a faculty of 20, and 160 graduate students. It has strong research programs in parallel and distributed computation, numerical computation, artificial intelligence, systems and software, databases, and theoretical computer science. The computing environment includes Vax-class mainframes, SUN-class workstations, Symbolics workstations, shared and local memory multiprocessors including an Intel Hypercube, Encore and Sequent multiprocessors, and an Alliant FX/8. A number of research activities in parallel and distributed computation are supported by an NSF-funded CER award. The Department is a principal participant in the University's Center for Applied Parallel Processing which has a broad interdisciplinary research program in large-scale scientific computation and operates a Thinking Machines CM2. There is also a satellite link to the supercomputing facility at the John Von Neumann Center in Princeton. Applicants should send a current curriculum vita to Professor Robert Schnabel, Department of Computer Science, Campus Box 430, University of Colorado, Boulder, CO 80309-0430. Applications are due by February 15, 1989. Late applications will be considered for any positions remaining unfilled on March 15, 1989. The University of Colorado at Boulder has a strong institutional commitment to the principle of diversity in all areas. In that spirit, we are particularly interested in receiving applications from women, ethnic minorities and disabled individuals. ------------------------------ From: David Hough <dgh@Sun.COM> Date: Fri, 6 Jan 89 21:52:41 PST Subject: Random Story It's not often that I apply what I learned at Berkeley to my daily work, which primarily involves finding very low-level bugs in hardware and software, mostly under development by other people. Since I have to test hardware with a wide performance range, benchmarks have to be adjustable in size so that they don't run too quickly on fast hardware to be timed accu- rately, nor too slowly on slow hardware to finish before that hardware is obsolete. So I have added adjustable parameters to a number of benchmarks. To calibrate them I run a little measurement program derived from the infamous Linpack benchmark. (When I first came to Sun I was so ignorant that I thought Linpack was a library of linear algebra subroutines rather than a benchmark program.) This little Linpack starts off factoring a 32x32 matrix. Even a Sun-2 can do that in acceptable time. If the time is too fast, it then automatically tries a larger matrix, up to 512x512. Then it computes what the execution time would have been for a 512x512 on the particular system, scaling the time for whatever matrix it settled on by (512/n)**3. Some Sun hardware currently under development has been getting fast enough that the calibration program tries 512x512. On both projects in question, however, I noticed that the program was getting hung up and taking an inordi- nate amount of time to finish the calibration program. This of course indicated a hardware bug, of which I informed the hardware guys and left them to find it. Oddly enough, the bug only affected IEEE single precision; double precision was fine; most of our bugs tend to occur in double precision for various reasons. Furthermore the bug didn't seem to show up in the 100x100, 300x300, or 1000x1000 single preci- sion Linpack benchmarks that I also run. In the first project the microcoder dutifully tracked things down with a logic analyzer to where an underflow was occurring. Now I knew that the Linpack benchmark generates uniform random data over an innocuous interval, and we all know that matrices composed of random data from a uniform distribution are remarkably well conditioned. I remember this particularly well because one of my Berkeley qualifying examination questions - put to me a week ahead of time to ponder fruitlessly - was to come up with a plausible expla- nation of how an eminent mathematician had conducted an empirical investigation of iterative improvement, studying published test matrices and matrices of uniformly- distributed random data, and had come to the conclusion that iterative improvement never improved the answer by more than one or two digits, which seemed to argue against what's routinely taught in elementary numerical analysis. Anyway I told the microcoder that there was still a hardware bug, but shortly thereafter something else changed and the calibration benchmark went back to 256x256 and there never was any other evidence of a single precision problem, so I quit worrying about it. Underflows, if they could have occurred, would account for the program apparently hanging up, because the way Sun obtains IEEE conformance on under- flow in systems built upon hardware like the Weitek 1164/5, is to trap on underflow and recompute the correct result very slowly in software. Such underflows are supposed to be rare. Then a totally unrelated but even more critical project ran into a similar problem. This afternoon I went to a high level crisis meeting attended by at least two vice presidents, at which I gloomily reported that a new, previ- ously unknown hardware bug had appeared that affected single precision. Upon returning from that meeting one of my colleagues, who'd been helping at the logic analyzer until he got suspi- cious, informed me that he thought there was no hardware or compiler bug, rather that the program had started to under- flow because the pivots had gotten too small and fallen off the end of single precision. What about the well-known wonderful condition of matrices of uniform random data, I asked? He suspected that the high dimensionality (512x512) was just too much for single precision. I wondered why the 1000x1000 benchmark worked in single precision. Since no progress was being made on the hardware bug, I started printing out the pivots in the program. The started out as normal numbers like 1 or -10, the suddenly dropped to about 1e-7, then later to 1e-14, and then: k 82 pivot -1.8666e-20 k 83 pivot -2.96595e-14 k 84 pivot 2.46156e-14 k 85 pivot 2.40541e-14 k 86 pivot -4.99053e-14 k 87 pivot 1.7579e-14 k 88 pivot 1.69295e-14 k 89 pivot -1.56396e-14 k 90 pivot 1.37869e-14 k 91 pivot -3.10221e-14 k 92 pivot 2.35206e-14 k 93 pivot 1.32175e-14 k 94 pivot -7.77593e-15 k 95 pivot 1.34815e-14 k 96 pivot -1.02589e-21 k 97 pivot 4.27131e-22 k 98 pivot 1.22101e-21 k 99 pivot -7.12407e-22 k 100 pivot -1.75579e-21 k 101 pivot 3.13343e-21 k 102 pivot -6.99946e-22 k 103 pivot 3.82048e-22 k 104 pivot 8.05538e-22 k 105 pivot -1.18164e-21 k 106 pivot -6.349e-22 k 107 pivot -2.48245e-21 k 108 pivot -8.89452e-22 k 109 pivot -8.23235e-22 k 110 pivot 4.40549e-21 k 111 pivot 1.12387e-21 k 112 pivot -4.78853e-22 k 113 pivot 4.38739e-22 k 114 pivot 7.3868e-28 SIGFPE 8: numerical exception, CHK, or TRAP stopped at daxpy+0x18c: movl a4@(0xe10),a3@ Those sudden drops were certainly perplexing - almost full word width, as if the matrix were actually exactly singular. Could there be a bug in the matrix generator routine (mat- gen) causing some wild data to be thrown into the pot? I looked and found a perfectly conventional portable linear congruential random number generator: subroutine matgen(a,lda,n,b,norma) REAL a(lda,1),b(1),norma c init = 1325 norma = 0.0 do 30 j = 1,n do 20 i = 1,n init = mod(3125*init,65536) a(i,j) = (init - 32768.0)/16384.0 norma = max(a(i,j), norma) 20 continue 30 continue Now you have all the clues. If anybody asks I'll post the solution in next week's issue. ------------------------------ End of NA Digest ************************** ------- Reposted by -- Kenneth R. Jackson, krj@na.toronto.edu (on Internet, CSNet, Computer Science Dept., ARPAnet, BITNET) University of Toronto, krj@na.utoronto.ca (CDNnet and other Toronto, Canada M5S 1A4 X.400 nets (Europe)) (Phone: 416-978-7075) ...!{uunet,pyramid,watmath,ubc-cs}!utai!krj