[Radiance-general] rpict/rpiece and multiple processors

[Jack de Valpine]

Hi Glen,

The -PP is used for memory sharing on a single host running multiple 
processes. If you have a machine with 4 cores then you will need to 
start 4 copies of rpiece. So with something like the following:

    rpiece -x 800 -y 800 -X 2 -Y 2 -F my_syncfile.sync <rpict options
    including -PP my_persistfile.pp> -o myimage.unf myscene.oct

    this command line would need to be run 4 times in order to get the 4
    processes up and running

This would result in an image split into a 2 by 2 grid and spread out 
over 4 processes. The memory including the scene would be shared among 
the 4 processes, thus reducing the memory footprint.

This can be automated simply using a Makefile or with other tools such 
as Perl or Python.

Let me know if you have any further questions and I can try to answer.

-Jack de Valpine

G HARDING wrote:
>
> Hi,
>
> I am rendering a number of images on a machine with multiple processors.
>
> I’m using rpiece with the –PP option (splitting into 4 pieces with the 
> hope of running one on each or the 4 processors in my machine), but 
> still only ever seem to be using 1 processor at a time.
>
> I get multiple rpict threads, but only one of them seems to do 
> anything at any one time.
>
> Does anyone know where I’m going wrong, or even if it’s possible to 
> use multiple cpus in the same machine at once?
>
> Many thanks,
>
> Glen Harding.
>
> Glen Harding
>
> Bradford School of Optometry and Vision Sciences
>
> University of Bradford
>
> BD7 1DP
>
> Tel: 07969 797391
>
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