Research activities and publications are briefly summarized. The major tasks reviewed are: (1) VAX implementation of the PISCES parallel programming environment; (2) Apollo workstation network implementation of the PISCES environment; (3) FLEX implementation of the PISCES environment; (4) sparse matrix iterative solver in PSICES Fortran; (5) image processing application of PISCES; and (6) a formal model of concurrent computation being developed

Pratt, T. W.

English

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https://ntrs.nasa.gov/search.jsp?R=19850023538 2020-03-20T17:30:11+00:00Z
(NASA-CH-176066) METHODS FOR DESIGN AbD
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METHODS FOR DESIGN AND EVALUATION OF INTEGRATED
HARDWARE`SOFTWARE SYSTEMS FOR CONCURRENT COMPUTATION
NASA Research Grant NAG-1-467
Semi-annual Report: September 15, 1984 -March 14, 1985
Principal Investigator: Terrence W. Pratt. Professor
Department of Computer Science
Universit y cf Virginia
Charlottesvil:e. VA 2.2901
This report briefly summarizes research activites and publications under this grant dur-
ing the second six months of funding (9/15/84 - 3/14/85).
Summary of Research Activities
The major tasks that have been performed are the following:
1. VAX implementation of the PISCES parallel programming environment. The implementa-
tion o; the PISCES Fortran 77/Unix-based programming environment was successfully com-
pleted on the DEC VAX under Unix 4.1bsd and 4.2bsd. The system is currently running
at ICASE and at the University of Virginia ar.J has been used for se,eral applications of
moderate size (discussed below,).
2 Apollo workstation network implementation of the PISCES environment. The PISCES sys-	 a..
tem was successfully implemented on a local network of Apollo workstations (10 Apollo
D\ 300 workstations on an Ethernet-like local network). This system implements the same
PISCES virtual machine that is available on the VAX, so that applications programs may
-un on either system without change in the code. The programme- sees the workstation
network as a	 single	 clustered parallel machine. Each workstation implements	 a PISCES
cluster. The programmer may distribute various parallel applications tasks to these clusters
using the PISCES Fortran commands.
In constructing this im plementation no attempt was made to optimize perfc,rmance: we
used the same basic implementation strategy as on the VAX. The goal \ v as simply to
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produce a first prototype for a study cf the viability of this sort of PISCES implementa-
tion. After impiementat.ion was complete. 'Fancy Fitzgerald studied the basic performance
of the system (a.; part of her Master of Science thesis [5], which also involved the imple-
mentation of the Apollo s_3stem). The basic performance parzmeters are the time to initiate 	 i1
a task and the time to send a message. Due to the amount of disk access involved in both
activities on the Apollos both task initiation and message passing were found to be unac-
ceptably slow for realistic applications. To improve this performance u'e would have to
change the operating system on the Apollos, which is not currentl y possible. As a result
we do not intend to pursue this implementation aL present.
3. FLEX implementation of the PISCES environmvrtt. Implementa*_ion of the PISCES sys-
tem on the FLEX/32 at NASA Langley is the highest priorit y item in our current activities
Prelim'.nzry design work has been done, but detail design has been dela yed awaiting release
of FLEX software documentation by the manuf;^.cturers. Implementation is planned for
summer 1985.
4. Sparse matrix iterative solver in PISCES Fortran. Merrell Patrick of Duke University.
in a collaborative effort with this project, designed a series of six variations on a general
parallel solution package for sparse matrix representations of linear systems of equati^zs.
These six variations were implemented in Pisces Fortran and run on the VAX implemenca-
tion of PISCES at ]CASE. The variations included a data love version. two chaotic itera-
tions, and various forms of communication (broadcast. direct send, etc) between the tasks.
These were used for system test and to measure differences in the number of messages and
the communication patterns between the different paradel versions. We found that even the
relatively small ]CASE VAX 750 provided acceptable performance for the:., studies. which
involved about 15 parallel tasks and up to several hundred messages. This work was
presented by Prof. Patrick at a workshop on parallel numerical methods at the University
of Texas in Austin hosted by David Ycung: a short paper will also be published [1].
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35. Irnage yroc:essing application of PISCES. Prof. Worthy Martin and Ph.D. candidate
	
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Ch°v -lim Tan of the U.Va. Computer Science Department are using the PISCES system for
an application of artificial intelligence techniques to an image processing problem: the track-
ing of moving objects in dynamically changing scenes. Parallel tasks are used to locate and
track different objects within the scene. which is continuously changing as nev , inputs arrive
from the camera. This work illustrates the potentiall y broad application of the PISCES
system. but is not supported directly by this grant.
6. Theoretical studies. 	 A new formal rn ,.de l of concur rent computation has been
developed by P.D. Stotts in a Ph.D. thesis nearing completion. The model is based on the
mathematical s y stem known as "H-graph semantics" (developed by the principal investigator)
together with a "timed Petri net" model of the para l lel aspects of a system- Stotts has
	
slaow , n tha. the model can be used for timing anal yses of hierarchical parallel systems and 	 I^
for automatic detection and resolution of conflicts in concurrent access to shared data. We
hope to use an extension of this model as the basis for a formal definition of the PISCES
virtual machine, which would be potentially of value to the PISCES implementor and user
A paper on this work will be presented at a workshop in Europe in summer 1955; a
technical report has been published [2].
7. Publications. A journal paper describing the PISCES design has beer, accepted for
publication in IF.F_E Soft% ,are, July 1965. a prepublication version is available as an )CASE
technical report [3]. A Ph.D. dissertation by P.D. Stotts [4] and an M.S. thesis by N.
Fitzgerald [5] are nearing completion. J. Ta y lor completed an informal project report [6] as
part of his Master of Computer Science degree describing his implementation of a perfor-
mance monitoring and analysis package for the VAX implementation of PISCES.
Publications List
[1) Patrick. M. and T.W. Pratt. "Communications Oriented r ;ogramming of Parallel Itera-
tive Solutions of Sparse Linear Systems." Communications in Applied Numerical Methods,
(to appear). Paper presented at the Workshop on the Impact of Parallel Architectures
..W'
on Numerical Methods, U. of Texas at Austin. March 1985.
[2) Stotts. P.D. and T.W. Pratt, "Hierarchical Modeling of Software Systemr with Timed
Petri Nets." International Workshop on Timed Petri Nets, Torino Italy. July 1985 (to
appear). Also published as Report 85-01, Computer Science Dept. Univ. of Virginia.
January 1955. 19 pp.
[3) Pratt. T.W. "PISCES: An Environment for Parallel Scientific Computation." IEEE	 1
Software, Jule 1985 (to appear). Also published as ICASE Report 85-12. (CASE,
NASA Langley Research Center, Hampton. VA, February 1985. 30 pp.
[4) Stotts. P.D. A Hierarchical Graph Model of Concurrent Software Systems, Ph.D. dissertation.
4
Computer Science Dept.. Univ. of Virginia (to appear).
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[5] Fitzgerald. N.J. Impiemen.tarion of a Parallel Programming Environment, M.S. thesis, Com-
peter Science Dept., Univ. of Virginia. May 1955. 50 pp.
[6) Taylor. J.A.. "Performance Analyzer for the PISCES System." M.C.S. 	 Project Report,
Computer Science Dept.. Univ. of Virginia. December 1984, 13 pp.
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Methods for design and evaluation of integrated hardware-software systems for concurrent computation

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