From: Rob Vasquez Newsgroups: comp.os.msdos.djgpp Subject: Re: DJGPP 1 -> DJGPP 2 -> slower program speed? Date: Mon, 20 Jan 1997 20:35:36 -0500 Organization: Digital Fx Lines: 23 Message-ID: <32E41D68.886@worldnet.att.net> References: <32E3510B DOT 29AF AT active DOT ch> NNTP-Posting-Host: 207.147.60.132 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp > But my disappointment was big. My program is about 20 times > slower using DJGPP 2 than DJGPP 1! I used the same compiler- > options (-O2 -m486) I also tryed by using -O6. But the speed > was the same: *much* slower. BTW I use GRX2.0 also. > > Who can help me make my prog faster (as fast as in DJGPP 1)? From the djgpp FAQ: ------------------------------------------------------------------------In general, GCC 2.7.2 which comes with DJGPP v2.0 generates tighter, faster code. But it sometimes produces buggy code when "strength reduction" optimizations are enabled. So DJGPP by default disables this kind of optimization, which might sometimes yield slower code. If you need extra speed, first debug your program with default optimization options, and then recompile with -fstrength-reduce switch to see if that makes any difference. GCC has a plethora of other optimization options which might make your code faster; the best way to know is to profile and experiment. -------------------------------------------------------------------------- Rob Vasquez Digital Fx '97 email: digital DOT fx AT worldnet DOT att DOT net