[Openmcl-devel] time travel

Alexander Repenning ralex at cs.colorado.edu
Fri May 15 22:56:13 PDT 2009

In some animations I found irregularities which I traced back to some  
strange behavior of mach_absolute_time

This loop should produce no output. On PPCs it works but on my Intel- 
Mac (with CCL 32) I get some output indicating that once in a while my  
computer appears to travel back in time for about 4 seconds

(dotimes (i 1000)
   (let ((t1 (#_mach_absolute_time)))
     (sleep 0.01)
     (let ((t2 (#_mach_absolute_time)))
       (when (> t1 t2) (print (- t2 t1))))))


Can anybody reproduce this and is there any explanation, work around  
for this kind of madness?


Prof. Alexander Repenning

University of Colorado
Computer Science Department
Boulder, CO 80309-430

vCard: http://www.cs.colorado.edu/~ralex/AlexanderRepenning.vcf

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