Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!aplcen!jhunix!barrett
From: barrett@jhunix.HCF.JHU.EDU (Dan Barrett)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: 	Lemmings - a tutorial Part V (last)
Message-ID: <7880@jhunix.HCF.JHU.EDU>
Date: 2 Apr 91 04:44:36 GMT
References: <781@tnc.UUCP> <mykes.0774@amiga0.SF-Bay.ORG> <dillon.5779@overload.Berkeley.CA.US>
Organization: The Johns Hopkins University - HCF
Lines: 42

In article <dillon.5779@overload.Berkeley.CA.US> dillon@overload.Berkeley.CA.US (Matthew Dillon) writes:
>There are many, many good algorithms,...

	Hear, hear!!!  Matt is absolutely right -- the algorithm is very
often the biggest key to obtaining speed in your program.

	In my programming courses (I teach CS at Johns Hopkins), my students
have been shocked to see the blazing speed improvement you can get by using
good algorithms.

	Here is a simple example:  raising a number to a power.  I took a
typical Power() function and raised a number to the 1,000,000,000 power.  It
took 30 minutes on a VAX 8530:

		double Power(double number, long exponent)
		{
			long i;
			double answer = 1.0;
			for (i=0; i<exponent; i++)
				answer *= number;
		}

{Now code the same algorithm in assembler.  Make EVERY little optimization
you like -- remove instructions from the loop, etc.  I guarantee that, with
this algorithm, you might shave off a minute or two from the run time.}

	Next, I changed the algorithm.  It made the source code TWICE AS
LONG (oh no!), and it even used (horror of horrors!) recursion.  The run
time dropped to 0.5 seconds.  Yes, you read that right.  0.5 SECONDS instead
of 30 MINUTES.

	Every programmer should read, read, READ those algorithms books.
You have the collective wisdom of ALL COMPUTER SCIENCE at your fingertips.
Use it and enjoy it!

                                                        Dan

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