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From: crowl@rochester.ARPA (Lawrence Crowl)
Newsgroups: comp.lang.c++
Subject: C++ on the Butterfly Parallel Processor
Message-ID: <23126@rochester.ARPA>
Date: Thu, 11-Dec-86 18:03:25 EST
Article-I.D.: rocheste.23126
Posted: Thu Dec 11 18:03:25 1986
Date-Received: Sat, 13-Dec-86 22:22:46 EST
Reply-To: crowl@rochester.UUCP (Lawrence Crowl)
Organization: U of Rochester, CS Dept, Rochester, NY
Lines: 52

Chrysalis++ is a C++ programming language interface to the Chrysalis operating
system of Bolt Beranek and Newman's Butterfly Parallel Processor.  Butterfly
Project Report 15 describes this system and is available for $2.50 in a check
payable to the University of Rochester and a US mail address by writing:

        Rose Peet
        The University of Rochester
        Computer Science Department
        Rochester, New York, 14627



                                 ABSTRACT

The standard Butterfly Parallel Processor's programming environment uses the
C  programming language and the Chrysalis operating system.  Chrysalis++ is
a C++ programming language interface to Chrysalis.    

Chrysalis presents an object-oriented view of the facilities provided by the
system.  Unfortunately, this environment requires a substantial amount of
detailed user code to represent, create, access, and delete the objects
provided by Chrysalis.  The code to perform these operations often must
override C's already minimal compile-time checking.  This, coupled with the
Butterfly's minimal error reporting means that any errors tend to be found
after much trial and error in the debug phase of program development.  

C++ also provides an object-oriented view, but its object management is much
simpler than Chrysalis object management with C.  The binding strategy for
the design of Chrysalis++ was to re-cast explicit Chrysalis object
management in C into the implicit object management that occurs routinely in
C++.  Chrysalis++ merges creation and access of Chrysalis objects into the
declaration of the variable used to represent them.  This strategy provides
the entire Chrysalis++ programming environment with one single object
management strategy.  

The development of Chrysalis++ highlighted some of the difficulties in mixing
a single process high level language with a low level operating system. 
Bringing C++ and Chrysalis together demonstrated weaknesses in the C++ class
mechanism and showed inconsistencies in Chrysalis object treatment.  This
development did provide some insights into the definitions of C++ and
Chrysalis that may help in designing future systems.  

This report is composed of three parts.  The first part gives a background
for this projects and describes the resulting Chrysalis++.  The second part
describes the experiences in developing Chrysalis++ in porting C++ to the
Butterfly and some of the weaknesses discovered in C++.  Finally, the third
part provides the details of Chrysalis++.  This last part is intended only
for actual users of Chrysalis++.  
-- 
  Lawrence Crowl		716-275-5766	University of Rochester
			crowl@rochester.arpa	Computer Science Department
 ...!{allegra,decvax,seismo}!rochester!crowl	Rochester, New York,  14627