Net2/usr/src/usr.bin/pascal/px/READ_ME

/*-
 * Copyright (c) 1980 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)READ_ME	5.2 (Berkeley) 4/16/91
 */

   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.