[Radiance-general] Parallel processes within rtcontrib

[Axel Jacobs]

Marija

> It works perfectly in Linux, but I couldn't make it work in Windows.
>
> For command like this:
> rtcontrib -n 2  -I+ -V- -h-  -b tbin -o outfile.txt -m sky  -f tregenza.cal
> @param.opt octree.oct<  points.txt
>
> I've got errors:
> bin/rtrace: fatal - command line error at '-PP'
> rtcontrib: system - select call error in wait_rproc()
> bin/rtrace: fatal - command line error at '-PP'

> Greg suggested that is could be a problem with file locking, but no idea how
> to solve this.
> Maybe some variables/flags should be set during compilation on Windows!?

I recently looked into various ways of running Radiance/LEARNIX on a 
Windows machine. Francesco's web site was down (fixed now), so I had to 
compile Cygwin Radiance myself. I did not try mingw, but believe it to 
be somewhat similar to cygwin in performance.

When running Mark's benchmark, I encountered the same problem that you 
are describing with rpiece. Trying to figure out why this wouldn't work, 
I played around with the bench4 makefile, and came to the same 
conclusion that Greg suggested. The syncfile which coordinates the 
different rtrace/rpict processes is opened multiple times, each process 
reading from and writing to the same file.

I believe it to be a 'feature' of the Windows OS that users are 
protected from themselves at all cost, so I'd be surprised if there was 
a mechanism that would allow you to disable this file-locking. Having 
said that, I am no expert in such matters.

If you have a multi-core machine and really need the extra speed, I 
suggest you look into running Radiance on LINUX inside a virtual 
machine. Sun's VirtualBox is very good and open source. It is comparable 
in speed to cygwin Radiance, but will utilise all cores/processors. You 
can double the speed again by running LINUX natively, to which there are 
a number of different approaches.

To get an idea about VirtualBox under Windows and the speed increase 
that you can expect, please see 'Running LEARNIX' which is available 
from the LEARNIX documentation page:

http://luminance.londonmet.ac.uk/learnix/docs.shtml

I know this doesn't really answer your question, but might provide an 
acceptable work-around for your problem.

Axel