Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!spool2.mu.edu!news.cs.indiana.edu!noose.ecn.purdue.edu!cidmac.ecn.purdue.edu!3ksnn64
From: 3ksnn64@cidmac.ecn.purdue.edu (Joe Cychosz)
Newsgroups: comp.arch
Subject: Re: reliable/reproduceable benchmarks on SGI MIPS box
Message-ID: <1991Jan3.035143.18865@noose.ecn.purdue.edu>
Date: 3 Jan 91 03:51:43 GMT
References: <11737@alice.att.com> <44383@mips.mips.COM>
Sender: news@noose.ecn.purdue.edu (USENET news)
Organization: Purdue University Engineering Computer Network
Lines: 127

In article <11737@alice.att.com> andrew@alice.att.com (Andrew Hume) writes:
>
>	I am running some benchmarks on a variety of machines
>and in particular, on a SGI 4D/380, a multiprocesor with 8
>33MHz R3000 cpus.
...
>	my problem is that I see quite large variations over
>multiple runs of the same benchmark, sometimes as much as
>1.26%. Now, the resolution of the timer is .01s and i should se
>an accuracy of about .01/40 or .025%. I am a factor of 50 off this.
>does anyone know how i can run these benchmarks so as to get reproducible
>timings? (i note as an aside that just running the benchmarks on the cray
>in multi-user mode yields variations of the order of .15% which is
>satisfactory).

I am puzzled why you think the accuracy should be .01/40?  Anyway my
experience with the 60hz and 100hz clocks is that they are not
exceptionally accurate and are suseptable to process switching.  Someone
gets the whole interval, even though they may have used only a small
portion of that interval. The Cray uses a very accurate clock which runs
at the cycle time of the machine (~6ns for YMP).

I do not know if SGI has made access to the hi-res clock on the MIPS
chip yet.

This doesn't really solve your problem here, but it may come in handy
when running benchmarks.


/* ----	second - Return user CPU time in seconds. ---------------------	*/
/*									*/
/*	Runction to return the elapse CPU time in seconds.  To properly	*/
/*	compute the elapse CPU time, the function should be called	*/
/*	twice, once in the beginning to get the initial CPU time, and	*/
/*	a second time to get the ending time.  The elapse time is then	*/
/*	the computed difference between the two times.			*/
/*	between the two times.						*/
/*									*/
/*									*/
/*	machine			low-res	  hi-res			*/
/*	Ardent Titan		  100Hz	  62.5ns			*/
/*	BBN Butterfly TC-2000	  100Hz					*/
/*	Convex C220		   60Hz	     1us			*/
/*	Cray 2, XMP, YMP	   ~6ns YMP				*/
/*	ETA 10			  100Hz	  P 24ns, P* 21, Q 19, E 10.5	*/
/*						  F 8.5, G 7		*/
/*	Gould 9080 and NP1	   60Hz					*/
/*	Silicon Graphics 4D	  100Hz					*/
/*	Sun 3 and 4		   60Hz					*/
/*	Vax 11/780		   60Hz					*/
/*									*/
/*	Author:								*/
/*	   J. M. Cychosz	12/15/89.				*/
/*	   Purdue University CADLAB					*/
/*									*/
/* --------------------------------------------------------------------	*/


#include <sys/types.h>
#include <sys/param.h>			/* HZ defined here		*/
#include <sys/times.h>			/* used by times()		*/
#include <sys/time.h>			/* used by getrusage()		*/
#include <sys/resource.h>

#if	ardent
extern	double	fputim ( double );
#endif

#if	butterfly			/* HZ not defined for BBN TC2000*/
#define	HZ	100.0
#endif

#if	eta10
#include <sys/syseta.h>

static int	Pico_per_Cycle;		/* ETA10 ps per machine cycle	*/

int asm	q8ic7	()	{
	tfc	%18
}
#endif

#if	gould				/* HZ not defined for Gould 9080*/
#define	HZ	60.0			/* or NP1			*/
#endif


/* ----	second - Return user CPU time in seconds. ---------------------	*/

double	second	()

{

#if	ardent			/* Ardent Titan: use internal MIPS clock*/
	return ( (double) fputim (0.0) );
#define	_CLOCK_
#endif

#if	convex			/* Convex C220: use 1us clock		*/
	struct rusage	res;

	getrusage (0,&res);
	return ( (double)
		 (res.ru_exutime.tv_sec + res.ru_exutime.tv_usec*1e-6) );
#define	_CLOCK_
#endif

#if	eta10			/* ETA 10: use real time clock		*/
	if  (!Pico_per_Cycle) 
	    (void) syseta (ETA_PSPERCYCLE, &Pico_per_Cycle);
	return ( (double) q8ic7 () * (Pico_per_Cycle * 1e-12) );
#define	_CLOCK_
#endif

#ifndef	_CLOCK_			/* Default: use low-res times() clock	*/
	struct tms	clock;

	times (&clock);

/*	HZ = 60.0	Convex, Sun, Gould, Vax				*/
/*	HZ = 100.0	SGI, Ardent, BBN Butterfly, ETA 10		*/
/*	HZ = function(cycle_time) on Cray 2, XMP, and YMP		*/

	return ( (double) clock.tms_utime / HZ );
#endif

}