To: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: Program fast w/BC++, slow w/DJGPP 
Date: Wed, 23 Nov 94 13:52:53 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>

A number of people suggested testing without memory managers
installed.  I've done this: no real effect.

Others suggested disabling the (secondary) cache just to see
if BC-compiled program fits in, while GCC-compiled does not.
This slowed down both programs, but the performance ratio stayed
the same.

I omitted the -O3 and -funroll-loops and put -O2 and -fomit-frame-pointer
instead, as some of you suggested.  This improved the performance
to some degree: it is now about 2/3 of the speed of BC-compiled program.

I've also seen that some of the screen functions cause mode switch
(e.g., wherex(), wherey(), clreol() etc.).  I will next comment them out
to see what happens.

A heretic thought started crawling into my mind: can it be that GCC
indeed *does* produce slow code for C++ programs?  I don't really
work in C++, so all my experience about GCC code efficiency comes
from C programs.  What about those constructors/destructors behind
the scenes: could it be they are much slower in G++ than they are
in BC++?  Opinions, anyone?  Maybe I will re-write the program in
pure C one of these days...

Thanks again to all people who wrote to me on this.