From: Young Fan <youngcfan AT hotmail DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Timing
Date: Thu, 08 Jul 1999 09:18:54 -0400
Organization: Nortel
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Message-ID: <3784A53E.EB898F54@hotmail.com>
References: <377CC7E6 DOT EB82B079 AT hotmail DOT com> <3780B0B3 DOT CE964094 AT hotmail DOT com> <3783E08C DOT 2BA33F77 AT cartsys DOT com>
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

Thanks a lot. I tried uclock, and it works beautifully when I restart in
MS-DOS mode.

Nate Eldredge wrote:
> The only one you need is `uclock'.  Thus:
> 
> uclock_t start, end;
> start = uclock();
> /* stuff to be timed */
> end = uclock();
> printf("It took %.15f seconds\n", ((double)(end - start)) /
> UCLOCKS_PER_SEC);
> 
> The cast to double is important to get resolution better than 1 second.
> 
> > Would I still run into problems with Windows about this if I restarted
> > in MS-DOS mode?
> 
> I can't imagine that you would.
> 
> > If the uclock doesn't work, how would I use the CPU's timestamp counter?
> 
> Here is a function to read the counter.
> 
> inline unsigned long long rdtsc(void)
> {
>   unsigned long long r;
>   asm("rdtsc" : "=A" (r));
>   return r;
> }
> 
> You can use it like `uclock'.  Just replace `uclock_t' with `unsigned
> long long', `uclock' with `rdtsc', and `UCLOCKS_PER_SEC' with your CPU's
> clock speed in hertz.
> 
> HTH
> --
> 
> Nate Eldredge
> nate AT cartsys DOT com