Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!topaz!klinzhai!webber
From: webber@klinzhai.RUTGERS.EDU (Webber)
Newsgroups: comp.graphics,comp.sys.amiga
Subject: Re: DBW-Tracer on UNIX
Message-ID: <214@brandx.klinzhai.RUTGERS.EDU>
Date: Fri, 1-May-87 23:03:42 EDT
Article-I.D.: brandx.214
Posted: Fri May  1 23:03:42 1987
Date-Received: Sun, 3-May-87 02:46:30 EDT
References: <213@ndmath.UUCP>
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 26
Summary: speeding up ray-tracing on unix
Xref: mnetor comp.graphics:589 comp.sys.amiga:4401

In article <213@ndmath.UUCP>, milo@ndmath.UUCP (Greg Corson) writes:
> Recently I was messing around with the DBW (AMIGA) ray tracing program on a
> SUN workstation here at Notre Dame.  The main program (RAY) compiles and runs
> just fine here, however there are some things that seem puzzling to me.  The
> documents to DBW tracer state the demo program "glass" runs for about 11 hours
> on an Amiga.  On the Sun with SKY floating point board it ran 14 hours...the
> only reason I can figure is that the Sun version might have automatically 
> calculated the picture to greater precision.  If anyone out there has actually

Well, I think you are close to the problem, but got it backwards.  On
most unix systems (including sun) it is faster to work in double
precision than single precision.  This is because all the libraries
are double precision, so anytime you pass a float variable or capture
a result in a float variable, a conversion has to be done.  You can
probably speed things up by changing all your `float' declarations
to be `double' declarations.  (Even when you pass a varible of type
float to a procedure whose formal parameter is declared to be of type
float, it still usually gets converted to double.)

There is also a big difference between a Sun II and a Sun III (as well
as among the various variations of Sun III), so it might be useful if
you were more precise than just saying a `Sun'.

Enjoy.

-------------------- BOB (webber@aramis.rutgers.edu ; rutgers!topaz!webber)