[Radiance-general] Fun with multiple cores and rtrace

[Randolph M. Fritz]

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


-- 
Randolph M. Fritz • RFritz at lbl.gov
Environmental Energy Technologies Division • Lawrence Berkeley Labs