[Radiance-general] Instances

[Jack de Valpine]

Hi Lucio,

This is somewhat confusing. -PP enables multiple process on the same 
machine to share memory. What is shared is memory space taken up by the 
octree. Ambient values are shared via the ambient file (-af), so they 
are not shared in RAM between processes (eg there is not a message 
passing mechanism for communicating back and forth between processes). 
At given points processes will write out the ambient data that has been 
calculated (by the given process) and held in memory to the ambient 
file. As processes do this they also read in the ambient values from the 
file (hope I get this right), so this is the method of sharing ambient 
terms.

-Jack

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# Jack de Valpine
# president
#
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On 1/10/2011 10:06 AM, Lucio Boscolo wrote:
> Sorry Greg,
>
> I feel a bit dumb, but still I'd like to understand this.
>
> If -PP is not sharing RAM, what memory is it sharing?
>
> Thanks for your help again.
>
>
> Lucio Boscolo Mezzopan
> Assistant Designer  |  Lighting
>
> Arup
> 13 Fitzroy Street  London W1T 4BQ  United Kingdom
> t +44 20 7636 1531  d +44 20 7755 6311
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>
> -----Original Message-----
> From: Greg Ward [mailto:gregoryjward at gmail.com]
> Sent: 07 January 2011 23:22
> To: Radiance general discussion
> Subject: Re: [Radiance-general] Instances
>
> Hi Lucio,
>
>> Thank you so much for your detailed answer (and sorry for being late again exploring it).
>>
>> -aa method is a good one, but I am a little concerned this will impact a lot on rendering time in a scene like mine in which many ab are required and a very high number of rays (it is a comparison between shading systems to work out transmittances).
> It doesn't necessarily take as long as you might expect, because the ray tree is very sparse after the first bounce (depending on the -lw and -ld settings).
>
>> The -PP option seems to be what I need, but I am not sure I understand it. Please tell me if the following is correct.
>>
>> I start an rpict (or rtrace) with a -PP namefile option.
>>
>> I start other rpict or rtrace wit -PP namefile (the same) and they will share memory (ram?)
> Correct, although new ambient values will not share RAM.
>
>> Ambient file instead will be shared by using -af and the same ambient file for all the processes.
> This will share the values themselves, which is critical for speed if -aa is not 0, but they will take additional memory in each process.
>
>> I believe -S is not needed with the -PP option, am I right?
> With rpict, you need to couple -PP with -S.  The rpiece program takes care of dividing a single image into pieces if that is your desire.
>
>> Can I share with -PP between rpict and rtrace processes?
> Regrettably no, you need a separate syncfile for rpict and rtrace, as they are different executables.
>
> Cheers,
> -Greg
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