From: Ed Leiby Newsgroups: comp.os.msdos.djgpp Subject: Re: Intermittent Run-Time of DJGPP App under Win95 Date: 26 Nov 1997 18:16:51 GMT Organization: Frontier Internet Rochester N.Y. (716)-777-SURF Lines: 43 Message-ID: <347C6732.718B@frontiernet.net> References: Reply-To: eiby AT frontiernet DOT net NNTP-Posting-Host: as5200-5-17.roc.ny.frontiernet.net 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 Precedence: bulk Eli Zaretskii wrote: > > On 22 Nov 1997, Ed Leiby wrote: > > > The problem is that it seems to run at two different speeds: As fast as > > Borland, and 2-3 times slower than Borland. I have tried using > > cwsdpmi,cwsdpr0 (rev 0.90+) and win95 DPMI server. > > Does this happen on all platforms (i.e., plain DOS+CWSDPMI and Windows > 95)? When running plain DOS ( version 4.00.950 ) I have never seen the faster performance. This is probably an important clue. > > > Any ideas ???? > > Compile and link with -pg and compare the profiles of fast and slow > runs. Maybe you will see what function takes longer, and that would > give a clue. I tried the -pg/gprof angle and was able to identify where a general purpose floating pt. complex correlation routine was showing a total ms/call of 0.04 ( slow case ) compared to 5.11 total us/call. Assuming ms=milliseconds and us =microseconds this is a ~8:1 delta. This routine is simple and seems to give the same results whether its running slow or fast. I was wondering whether or not alignment might not be a factor in this. Is there anything that win95 could do at run-time to change the alignment of float data? If so, what is the difference in machine cycles between a float access for a "good" alignment and a "bad" alignment? Would this affect both reads/fetches and writes? If a misaligned access is cached, is there a subsequent cycle hit on all further fetches? Sorry for all the questions, hope they're close enough to topic. I also hope somebody will answer them. Thanks, Ed Leiby Ed Leiby