[Radiance-general] running radiance on multiple cores

[Greg Ward]

Yes to #1, no to #2.  This was discussed before, and I added a warning from rpiece when the resolution changes, but I can't keep it from changing.  Rpiece (rpict really) needs the tiles to be of equal size, which means both dimensions must be multiples of the respective number of tile divisions.

You can work around the problem with some difficulty by noting what rpiece changes the resolution to and making sure you set -x and -y to this with -pa 0 on any other runs you do.  Unfortunately, the actual resolution will change with different -N settings because rad will make a different number of tiles to optimize processor loads.

Regarding #1, I haven't changed trad in ages, so it may take a while to remember enough Tcl/Tk to add this.

Best,
-Greg

> From: Terrance Mc Minn <t.mcminn at curtin.edu.au>
> Date: May 23, 2012 9:28:34 PM PDT
> 
> I can verify that missing sections of images happens on both Linux and MAC computers when an ambient file is used though not consistantly.
> 
> Often I have suspected/verified that the number of -N specified is greater than the actual number of cores available. For example a i7 Macbook that a student had in my office 10 minutes ago shows only 4 cores hence -N 4 would seem appropriate. Some images would complete while others left black patches. All I did was to delete the offending hdr image and re-issue the rad command exactly to have the image rebuilt - much faster as the ambient file has already been populated.
> 
> I suspect that the -N number should generally be kept to at least 1 below the max cores available.
> 
> Questions for the Development List :
> 1) Can multi-core processing be added to trad  (-n for rvu and -N rad)? While it is possible to add a -n 4 in the trad options line for rvu, you cannot use a -N in the option line for rad.
> 2) Can the image size resolution for single core processing be the same as multi-core to allow further processing with falsecolor. When rad -N processing uses rpiece the image size can be modified/rationalised. This does not happen in single core processing, hence falsecolor would fail when mixing images due to image size mismatch.
> 
> Terrance Mc Minn