yII M;'dIIWAR[ AND AR . 01MARY AND INIVIo I7A11i 11old PARH FiIOGC PRfRMMr N AN MBADPAA ,

PAR DI 4 P 4 f C M OIFR 'CIFN F KfI t '11A'. I II II I [ H ? I 84 0004 At ',R 2 030 11ND

' :---'-,.F- -

... ,- - - -

1.0 I 2

11112=5 14 131.6

iiIi - lii.,11

MICROCOPY RESOLUTION TEST CHARTNATIONAL B REAU OF STANDAROS - 93 A

IL

fo

.. , .

• ,V

-

UNCLASSTITD

SECURITY CLASSIFICATION OF THIS PAGE (Whin DateBnieres0REPORT DOCUMENTA.TION PAGE READ INSTRUCTIONS• BEFORE COMPLETING FORM

GOVT ACCESSION NO. S. RECIPIENT'S CATALOG NUMBER

AFOSTE. 0 00044. TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED

PARALLEL LOGIC PROGRAMMING AND ZMOB AND PARALLEL INTERIM, I JUN 82-15 SEP 83SYSTEMS SOFTWARE AND HARDWARE,

s. PERFORMING 046. REPORT NUMBER

7. AUTHOR(&) S. CONTRACT OR GRANT NUMBER(s)

Jack Minker and Mark Weiser AFOSR-82-0303

S. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK

AREA & WORK UNIT NUMBERSDepartment of Computer ScienceUniversity of Maryland PE61102F; 2304/A2College Park MD 20742

0 It. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

Mathematical & Information Sciences Directorate SEP 83Air Force Office of Scientific Research//f.. IS. NUMBER OF PAGES

Bolling AFB DC 20332 /00 14. MONITORING AGENCY NAME & ADDRESS(If different from Controlling Office) IS. SECURITY CLASS. (of this report)

OUNCLASSIFIEDIS.. DECLASSI FICATION/DOWNGRADING

SCHEDULE

~4 IS. DISTRIBUTION STATEMENT (of this Report)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different fro Report)

IS. SUPPLEMENTARY NOTES

A19. KEY WORDS (Cont e en rever eside.. It necesay and Identify by block nu r)

33 fo. ABSTRACT .(C-mnti, an revere side Of necessary and Ideify by Week a or.)During this period the investigators had four papers accepted for publicationin refereed conference proceedings, two papers appeared in an invited workshopand one technical report and one technical note were written. Titles include, i'

'-AJ Interfacing predicate logic languages and relational databases,9 9A parallel-J inference system based on logic,# 1A theory of forward and backward tracking,#

and $Design of the intensional database system of the ZMOB parallel problemsolver.9 The hardware side of the project is progressing but ZMOB does not

s.a exist yet as a working system.

DD_ , 1473 toliBoN o I Nov so IS oa LeTe UNCLASSIFIED

SECURITY CLASSIFICATION OF THIS PAGE (Ch1fate 0....

4 . a-

-- -p-. ....

AFOSMTR- 84-0004

Parallel Logic Programminlg and Z7M(JB

and

Parallei Systems Sotware and Hardware

A Summary of Work Performed for the Air Force Office

of Scientific Research

June 1982-September 15, 1983

by

Professor Jack Minker

and

To Asst. Professor Mark Weiser

TA Department of Computer Science

University of Maryland

College Park, Maryland 20742

. jlab,-,yCodeS.& i and/or

820198

84 0 9 140 jLroe tor pbli r1.

distri-utiij-1L

*1I'h purpose of t his letter is toi discus-3 our research into parallel systerns softwatre and hard ware, a~nd

parallel problem solving*i"& d under A~rr Grant *K840.Udrt cretga.

detailed design and partial implementation of a parallel problem solving system, PRtISM ( parallel infer-

en1ce q~ystrrn4. based on logic was achieved. The PRISM requires that the Z\101 parallel pr')ress4)r be

aLVAilthle for use. In addition. systems software ind hardw.tre have been developed. It is estimiated that

ZM011 will become available for use during the Fall of 1983. Hence, a full test and debugging of PI'lSMf

cannot lbe achieCved( under the current grant.

At te ed o th curtntgrat w exectto have accomplished, as a minimum, all of the objectives

prsopo%ed. That is, in th- area of parallel problem solving, the initialPRISM has bre fully designod; imdi-

vidua.l I iogratins have been implemented and tested in a non-parallel1 environment-, and i nvestigat ions have

beena mrade into extensions to the initial design. As a consequence of the work, six papers were aCCpted

for publication in conference proceedings, and one technical note was written. Other papers are in pro-

gress and will be completed before the end of the current grant.

2. .4ctomphipshments on Efforts During Period June 5,19Sf-Seplember 15,198

In section 2.1 we discuss work accomplished in parallel problem solving, and in section 2.2 we dis-

cuss work in parallel systems software and hardware. We describe the accomplishments made as of AugustI

15i and those expected by the end of the grant,September 15, 1983

2 1 Z.MOfl and Parallel Problem Solting

D~uring the period June 30.1982-September 15,1993, we proposed that three major tasks be accom-

1aj D~esign of an Initial Parallel Logic Problem Solver. Follow $Poo

(b) Implementation of the initial design. Rust availablcoy

153I:eieSxtesi7sto the initial design. Titchc rPACWhI benV:C ~d~ j

In he ollwin theesections we describe progress Made 00 these effortS. In the fourth section, we

decrbepuliaton adreports written, that describe the wq" fb WI ippR~t (ALsI

MATThW 3. *MChief. TechnicalIntrsinDvso

2.1.1 I),Ogn of an Intial I'rallri L,,jir Problrm Solver

The fNnetioual ipecific:tion of a hy:,tem teried PRIS M (ParAlel Inference System) was ,'en.oiti.d

coimpleted Ifore the start of the effort. A document termed 'Functional Specifications of thi. ZMB)l1

Problem Solver- was written and completed during the period of the grant and provides the complete

func'iunal spe'ification of the system.

The detailed design of the functional specification is completed. Some modiflcations may he made

as the system undergoes implementation.

o!.. Im plrmentation

The implementation of PRISM requires the availability of ZMOB. The ZNIOB system is not yet

fully available to support the complete implementation of PRISM. A stand alone Z8OA system that was

submitted for bids during May 1082 has been approved by the University for purchase and delivery was

made in February 1983.

Substantial progress has been made on implementation in spite of the above equipment status. The

status of the major parts of the design is as follows.

(I) lVor interface with VAX

The program provides the interface between the user and VAX, the host computer for PRISM. The

program has been implemented and is tested. A full test will require ZMOB.

12) E',rtnsionill Databas e (EDD) for loblts The Extension-d Database (EDB) resides on mohlets. An

assembly language program has been implemented and runs on a single Z80A. When the entire rela-

tional table resides on a single moblet, the EDB code responds to queries. The program is partially

tested and the code that supports the distribution of the EDB on several machines exists. Testing

requires the availability of ZMOB.

(3) L':tr n.4iv nal Database for VAN

The EI)l is constructed by the user in the VAX machine. The database supplied by the user is

stored initially in the VAX. Syntax checks are performed on the input data, and errors are report, d

to the user. The data is then indexed, and formatted for transmission to the appropriate number of

moblets required. Implementation of this portion of the system is in progress and is expected to be

*'

Substantially fcompleted prior to September 15, 19,43.

() lhtenional Database fIDb) for ZAIOIB and Monitor

The Inteion iI )ataa.we (11)l1) stt,rcs the prce'dure-s in the system. 'rhe initilA deigf olt ,% Iot per-

mit the number of procedures to exceed the size of a moblet. The IDIJ ha. been implemented in

Pa.cal and is being tested on the VAX. The program has been converted to C for the millets.

Debugging of the code will require ZM(II. 'The IDB monitor has been implemented and is being

t.sted.

(5) Int neional Database (IDB) for V4X

As with the EDB, the IDB is entered into the VAX by the user. The program does syntax checks on

the input data, coordinates with EDB data provided by the user, indexes the procedures and

prepares the programs and data for transmission to the moblets. The program has been imple-

mented and tested. It has been interfaced with the user interface program. It must be tested in

conjunction with the ZMOB.

(6) Problem Solving Aachine (PSM)

The Problem Solving Machine is the central portion of PRISM. A stripped-down version of the

design has been implemented in PROLOG and is running on the VAX. The full PSM program has

been implemented in PROLOG and converted to C, so as to improve efficiency. The PROLOG pro-

gram will then serve as a high level operational and axiomatic definition of the PSM. The code has

-, to be debugged and requires the availability of ZMOB.

(7) Communication Primitives

The communication primitives have been implemented and require ZMOB for a full test.

To further the implementation, a portion of ZMOB is simulated on the VAX and interfaces with the

exi..ting programs. A primitive system consisting of the user-VAX interface, the IDB programs, and the

stripped-down version of the PSM. on a simulated ZMOB belt. has been tested. This has permitted us to

tet several portions of the system together rather than in isolation. C£.I. Inzrestigate Eitensions to the Initial Design

, IL

4

*rhe I'riuutry emphasis since the 3ward of the current grant has been dlirected towards the de.-ign

311d iria plerii.:tatiiia of PRUISM. Simultaneously extensive investigations were madme on a number of toirc

as~ dw"scribe d below.- We expect to have some of these efforts ini an advanced stage of comrpletio~n by s ep-

teniher 1983 mid otheri will require substanltial work during the next year's proposed elffort.

(a) Exte rvtions to the Problem Softiag Machine

Considerable progress has been made on this subject. Our initial design has been extended to

include a limited amount of AND-parallclim. Further work will be performed on achieving full

AND-parallelism,

Consideration is being given to the control structure in general. A theory of backtracking has been

developed for function-free problems. A technical report has been written that describes how onec

can take advantage of integrity constraints.

Work on control structures will continue into the next year's work.

(b) 11)1 rzitrnsiona

Work is starting on the design for the IDB which will permit extension to procedures that exceed the

size of a single moblet.

(c) Ilackend Database Machineit anid Peripheral Devices

A study has started on backend database machines to determine their availability. Once this is

done, considerations will be given to interfacing with such systems. Considerations as to how to

interface with a relational database machine have been given as described in Section 2.1.4, below.

Tot he an effective tool in a research environment, additional features must be added to PUHISM.

l'reliniinary considerations are being given to the gathering of statistics; providimg the user the abil-

ity (4) view the proof tree structure as it is evolving; and recovery in the event of system failures.

We expect to have a preliminary functional specification of thesie areas by September 19M.

".1.4 I'ublicrations and Refporlu

Aii a consequence of work performed on this effort, four papers were accepted for publication in

refereed ronference prorredings, two papers appeared is a invited workshop, one additional technical

aI

r,.p.,r! was written and one technical note.

[He puIli'ations and reports cover a number "f differrnt topics function a description and ,let:ail'-l

1,,- ign; 'ISI.M syteui and alternative aspects; rontrol structures; and interfacing logic prtr:,in% and

(.& Funrtional De'scription and Design

In III a functional description is provided of'the PRISM. The description covers the 1')l1, the )I11.

the iD)11 monitor, the user interface and the PSM. A detailed lescriptiOn tf the design of the It11 is

providrd i, n2J. 'i-se reports are intended for internal ,lse and will not be submitted to jowrnals.

(b) l'RISM .yt I

Aspects of the PRISM appear in a number i)f papers and reports. In 1] we present the initi:l ideas

that led to the ultimate design of the system. The paper 15) is a condensation and minor revision of

the earlier report. Aspects of the PRISM system are covered in papers 121, 161, and 181. The heart of

the PRISM, the problem solving machine (PSM) is described in 161.

(c) Control Structures

A theory of intelligent forward and backward tracking is provided in 171. The theory applies to

function-free problems and describes how lemmas and integrity constraints may be used during the

search process.

(d) Into rfacing Logic Programs and DatabaseI

Various possible ways in which a database may be interfaced with logic programs are discussed in

[:t]. Aniong the options described is the combining of object language and meta-language state-

netits.

o2 ork ('omphltrd

The Zinob computer is composed of 256 Z80 computers connected on an intelligent high-speed ring

h!,. called the "conveyer belt". It has been described extensively elsewhere. Each Z80 has 61k bytes of

meniry, a parallel port, a serial port, and a floating point chip in addition to its conveyer belt connec-

ti, n Initially Zmieb will be completely dependent on a host computer for downloading of programs and

for in:'s ,t!torage. The Iost will be the Department of Computer Science's Vax-11/780, or a dedicated

| Y |,,1

-tp

S

VxLx i urchxced undler grants pending lnder the Do)D special cquipment program and the Nation:rl lerc

Fioliod at lin.

Individi.i Z O's with asstoiated hardware are cralrd "nhoblets*. A m-blet ri.nist.s of 1 ZI ;$Il :

"mailsterm or m.ailbox'. Mailboxes are tied together on the "belt". The, mailst,,ps asociutd with h t

commillun ications are "Vaxstops "

The Zmb basic design has been checked in two-moblet versions both wire-wrapped and on printed

circuil boards. Multiple processors can run independently, as many as necessary (up to 16 have been

tested). A berious glitch was found in the processor card in January 1983, and since then there have te.n

no processoAr failures.

Hardware debugging has focused on communications between the processors. The four components

of the communication system-the master clock, the clock cables and backplane, the backplane intercon-

nect cables, and the mailstop boaeds-have each undergone several revisions. The clock circuit is being /tuned to provikle optimal timing between the clock and index pulses to the moblets. Several versions of

chick cable are being tried, including coax, twisted pair, and shielded twisted pair. The clock cables are

critical because they must run for several yards to distribute clock to all the processors. Deglitching capa-

citors on the backplane have eliminated some noise, and pull-up resistors on the mailstop hoards have

been adjusted for better noise tolerance. A logic analyzer has been rented to better view multiple mail-

stop signa s.

Coimmunication is reliable in one direction along a single b3ckplane. A complete communications

low)p ran be athieved for several seconds without a failure. The problems are not unexpected and pri-

wiarily involve noise and timing relations with the master clock.

S ." S)(I%% are

There are three main projects looking with applications for Zmob. These are the Computer Vision

project with ('rofeswirs It enfeld and Davis, the Distributed Numerical Computation project with l'rofrs-

Notr.s Stewart and t)'.eary, and the Distributed Problem Solving project with Profes.or Minker. L'ach

plan" to use Zmb to explore parallel processing algorithms in their speriic dcvmains, and each faces the

4------..

-- I.

7

Idol, m 4)f iopermting qysteln support for coordiniatng the pr wesses and accessing the powerful Z.ihol

Thes.e three )rjecLs need similar bLsic operating .ystem utilities. The projects' irupl,.i.nt-rtion

strategies have been driven by the Zmob conveyer belt hardware design but none of the projects envisis,

woiking at the machine code level at which the conveyer belt can loe directly accessed. Each requires

high-level language access to the full conveyer belt-capability.

The system utilities for use by all three projects are under development. In particular, the following

st-ftware has been completed and is fully documented on-line the Computer Science Department's Vax

I. c - Run Whltesmlths C compiler for zSO/smob2. belt - primitive routines for smob mail stops3. 1ol - 1O library for smob.4. sfasl - Load a smob program at 0600 baudS. ago - transfer a program to the smob, and go6. sload- load the smob's memory

Software' working but for which documentation is still being readied includes:

(I) Z80 Simulator This emulates the basic Z80 processor without the Zmob environment. It was the first

emulator to be completed and provided initial experience with the Z80 environment. It is a

Kuff iciently detailed emulation to permit running CP/M and Prolog, a capability much used by the

distributed problem-solving group.

(2) C'ommu ications Simulator. This emulates multiprocessing and use of the mailstop and conveyer

belt environment but executes Vax C code rather than Z80 machine language. It performs multipro-

Cc. sing using basir Unix capabilities. The interface to the conveyer belt uses the same high level

language call.% that will be available on the moblets. Check out has been via an implementation or a

solutiom to the dining philuiophers problem.

(3 n (umiimunications Activity Display. This system accepts a stream of input describing the belt

activity and dil)lay-4 on a color graphics display the resultant belt status. The input stream is now

generated by tile communications simulator (see above) and will eventually be generated by the

mimitor mail stop' on the actual Zmob (see below).

8

III S vter I)ebggin. Ilarness. This permits dehogging new lw le'vel sy-tem softw.tre for i;,li,ion in

Z/iolo. It allow% (te te.ter to manu:,Ily ereate conditions which in :utcial praitice would be lIn *.

r ta.,, ilhU. t-jtn the robustnet of the system. It consit~s of three parts- (:%) lite % yterla -tv.are

a, nder test. (b) the 1atoh0et simnlation system, and (e) the user interface display connectedl to both (;S)

and fit). The s. stein Aoftware under test believes that it is running within a mnotlet, as emul:Lte l by

the inblet Simulation system. In fact, however, all attempts at communication are simply

displayed to the user via (c). The user can then specify any arbitrary response on the part of the

hardware, in-ludinA timing relationships. The right half of the user's display is reserved for interac-

tion about attempts at moblet communication. The left half of the display can be ii-ed by the sys-

to-m under test to display internal status of interest to the user.

(5) Multiple-window Communications Interface. This is an adaptation of the maryland window shell to

problems of communications with the Zmob. The window shell allows arbitrarily sized and posi-

tioned rectangular windows on a single CRT screen, each functionally equivalent to an independent

terminal. A typical application is to open several windows and run a communication pro:ess to a

different moblet in each window.

II'

I

'#

i9

.Y. I/efrrres

[II \fiker, I., et 1. "Functional l),cription of the Z%10I P:irall lProblern Solving 5y t.m". lSy.,'ii.

1",l Note I, l)epartment of Computer Srience, U niversity of Marland. D).reilbr 1982.

[2 ( t:. D, -)eign of the Intensional Databavse System of the ZMO 1arall*I Problem Solver-. Tich-

ir:d 1ieport ('Conmputer Science Department, I 'niverity ft Maryland, 1982.

31 (hakravarthy, U.S., Minker, J. and Tran, D., -Interfacing Predicate Logic l,anguages and latit

l)at:Lb:L-e%'. Proc'redings of tht Firsi Internaitionmal Logie Progranming e7-,nmfrrrne, September

17, 1982, Faculte des Sciences de Luminy Marseille, France, 91-98.

[i li ainge . N.. Kabif. S., and Minker, J., "Logic Programming : A Parallel Approach". Technial

iR.',ort nt-il121, Computer Science Department, University of Maryland, December 1981.

'i:.in,'r, N., Kasif, S., and Minker, J., "Logic Programming : A Parallel Approach", Procerdings of

thf Firslt Inlernaiunal Logic Programming Conference, September 14-17, 1982, September 14-

17,1982, Faculte des Sciences de Luminy Marseille, France, 71-77.

[(;I Ka, if. S., Kohli, M., and Minker, J., "PRISM - A Parallel Inference System Based on Logic", Techn-

ical leport TR-1213, Computer Science Department, University of Maryland, February 1983.

171 ohli. NI., and inker, J., "A Theory of Intelligent Forwsrd and Backward Tracking", Technical

Ileport I in preparation), Computer Science Department, University of Maryland, March 1983.

11 \linker, J.. et P Problem Solving on ZMOB", Proceedings of Trends and Applications 83,

\Vashinglon,

I ..- .-.- -4- -