usr/src/cmd/px/READ_ME

Copyright (c) 1979 Regents of the University of California

   This directory contains the source code for the Version 7 VAX
interpreter for Pascal. Following standard convensions, the makefile
contains four commands:

        px - compile px

        install - compile and install px in /usr/ucb

        clean - clean out directory

        print - print out a listing of px


Bugs and Limitations:

   Runtime error messages could give far more information than they
currently do. (eg the actual value of a subscript which is out
of range)

   It should be possible to resume execution following many of
the runtime errors. (eg fixed overflow, interrupt, etc)


Comparison of Pascal with C compiler

In an attempt to compare compiled versus interpreted execution speeds
the 'Tower of Hanoi' benchmark (see hanoi.p, hanoi.c) was run with
the following results:

Data:
        number of disks:                   16
        number of moves required:       65535

Compiler, Flags           Compile       Compile          Run     Run
                           Time          Factor          Time   Factor
Pi, full tests           0.4u+0.4s        1.0           42.7u     1.0
Pi, no tests             0.3u+0.3s        0.7           35.2u     1.2
Pc, unoptimized          3.8u+2.4s        7.7            5.3u     8.1
Pc, optimized            4.4u+2.3s        8.4            4.6u     9.3
C, unoptimized           1.7u+1.8s        4.4            2.8u    15.3
C, optimized             2.0u+2.0s        5.0            2.5u    17.1

Note: The times for Pc and C were obtained by running larger
problems and scaling the run times down appropriately.