[Radiance-general] Re: rtrace and parallel processes

[Greg Ward]

Hi Cramer,

You don't need to "pregenerate" the ambient file for rtrace purposes,  
but you can.  The disadvantage is that it will take about as long to  
pregenerate the file as it does to run rtrace, though the subsequent  
run should go very fast.

Sharing values via an ambient file with -aa non-zero allows parallel  
processing to actually work in Radiance.  It doesn't require a  
precalculation, though.  The only reason to do that is to get slight  
more accurate and/or smoother results.

Cheers,
-Greg

> From: Cramer Silkworth <silkworth at transsolar.com>
> Date: July 2, 2010 12:48:40 PM PDT
>
> Jack, Rob, et al,
>
> I read Rob's posting and have been playing with -aa, but I'm not  
> sure I know what I'm doing. Here's what I've got:
>
> this: rtrace -n 4 -I+ -h -ab 8 -ar 128 -aa 0.1 -ad 1024 -as 512 -e  
> grid.log cie10k.oct < grid.pkt > grid.out
> takes 23.5 minutes, for 3780 measurement points.
>
> this: rtrace -n 4 -I+ -h -ab 8 -ar 128 -aa 0 -ad 1024 -as 512 -e  
> grid.log cie10k.oct < grid.pkt > grid.out
> (-aa 0 is the only change) takes 13 seconds for the same measurement  
> points, but yields daylight factor results (calc'd with an rlam| 
> rcalc line following this rtrace call) 30% lower on average.
>
> Andy's email to Rob via this list (and posted as an update to Rob's  
> blog post) mentions an ambient file. Is there a way to "pre- 
> generate" this file before starting rtrace, such that each process  
> will use it? Or am I just totally confused here (=yes).
>
> Thanks,
> Cramer
> -- 
> Cramer Silkworth
> 212 219 2255 | silkworth at transsolar.com
> Transsolar Inc. | 134 Spring Street Suite 601 | New York, NY 10012
>
> Transsolar Climate Engineering
> Technical consulting for energy efficiency and environmental quality  
> in buildings.
> New York - Stuttgart - Munich