[Radiance-general] Fun with multiple cores and rtrace

[Jack de Valpine]

Hi Randolph,

Not sure if this is related, but I recall that Rob Guglielmetti looked 
into rtrace performance in a parallel setting:

http://www.rumblestrip.org/interests/light/rtrace-multiprocessing-option-initial-test-results/

-Jack

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# Jack de Valpine
# president
#
# visarc incorporated
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#
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On 2/3/2011 11:49 AM, Randolph M. Fritz wrote:
> Sensparm.opt attached.  What's striking is the way some of the rtrace 
> processes seem to "get ahead" of the others.  It was actually worse 
> before I took that ps snapshot, with the last two processes having 
> accumulated run times of 30 minutes or so, while the first six had 
> only run about 10 minutes.  The same sensparm.opt file (modulo a 
> change of a -sj) continues to work as expected on dino.  The main 
> things I changed seems to have been installing os updates and bringing 
> Radiance to its head version, but I am actually suspecting an os glitch.
>
> Randolph
>
> sensparm.opt:
> -dp 2048
> -ar 49
> -ms 1.9
> -ds .2
> -dt .05
> -dc .75
> -dr 3
> -sj 1
> -st .01
> -ab 5
> -aa .075
> -ad 4096
> -as 2048
> -av 0.01 0.01 0.01
> -lr 12
> -lw .0005
>
>
> On 2011-02-02 22:14:52 -0800, Greg Ward said:
>
>> Hi Randolph,
>>
>> What is unexpected about this process status?  You asked for -n 8, so 
>> you get 8 active processes and one that collects the results.  They 
>> are all duplicates of each other.  What are the exact circumstances 
>> of the slowdown?  What options are hidden in your sensparm.opt file?
>>
>> -Greg
>>
>>> From: "Randolph M. Fritz" <rfritz at lbl.gov>
>>> Date: February 2, 2011 9:29:55 PM PST
>>>
>>> I finally managed to get Linux going on my modelling system, an 
>>> eight-core
>>> ThinkStation.  It was running Radiance very fast.  Then I started 
>>> seeing ps
>>> output like this:
>>>
>>> 6589 ?        S      0:00 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>> 6592 ?        R     29:32 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>> 6593 ?        R     29:32 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>> 6594 ?        R     29:32 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>> 6595 ?        R     29:32 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>> 6596 ?        R     29:32 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>> 6597 ?        R     29:32 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>> 6598 ?        S     41:03 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>> 6599 ?        S     49:48 rtrace -n 8 -h -I @sensparm.opt ot-3.oct
>>>
>>> And it slowed down by a factor of three. My impression is that there 
>>> has been an
>>> OS glitch and it is in fact only using one core.  Anyone else seen 
>>> this?
>>>
>>> Head Debian build of Radiance, Ubuntu 10.10, most current version.
>>>
>>> Randolph
>
>