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MathGroup Archive 1999

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Timing[] and AbsoluteTime[].

  • To: mathgroup at smc.vnet.net
  • Subject: [mg20257] Timing[] and AbsoluteTime[].
  • From: Guilherme Roschke <gr at network3.entropy.upenn.edu>
  • Date: Sun, 10 Oct 1999 00:04:08 -0400
  • Organization: University of Pennsylvania
  • Sender: owner-wri-mathgroup at wolfram.com



How does timing measure its "value"?

here is my problem.  I have fuction f[x], which does a few hundred
NIntegrates.

Timing[f[x];]

= {1770.60,Null}.

However:

before=AbsoluteTime[];  (# of secs since 1/1/1900)

Timing[f[x];]
 = {1770.60,Null}

after=AbsoluteTime[];

Diff=after-before

= 14,673.000


Timing is off by a factor of 10!

Note that this is on a DEC with 2 21264 500mhz Alpha chips, where nothing
else is running except for the system deamons (lpd, sendmail, xserver
etc...).

This is especially disconcerting because the AbsoluteTime[] elapsed is
closer to a PII350 that I have than I would have hoped for in doing
numerics on the Alpha machine.

Does anyone have any thoughts of what might be going on?  On how I could
actually receive my answer in 1,700 rather than 14,000 seconds?

I'm using version 4 for Digital Unix.



thanks,

Guilherme

*************************************************
Guilherme Roschke			 	*
Programmer/SysAdmin/Researcher			*
Dept. of Anesthesia				*
University of Pennsylvania Medical School	*
gr at network3.entropy.upenn.edu			*
*************************************************






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