Re: no parallel speed up ?

Smith, Ian wrote:
> 
>> -----Original Message-----
>> From: Brian Paul [mailto:[email protected]]
>> Sent: 06 February 2008 02:25
>> To: Smith, Ian
>> Cc: [email protected]
>> Subject: Re: [Chromium-users] no parallel speed up ?
>>
>> Smith, Ian wrote:
>>> Hi,
>>>
>>> Apologies if this is a rather naive query but I'm extremely new to chromium
>> ...
>>> I'm trying to see if I can use a Linux cluster to parallel rendering. I've
>>> tried the atlantis application with crdemo.conf and crdemo_full.conf but
>>> as far as I can see the full version with two tiles seems to produce the
>> same
>>> frame rate as the single tile version with crdemo.conf. I've got the
>> crserver's
>>> and the crappfaker running on separate nodes but the frame rate stays
>> around
>>> 10 fps. I'm I missing something here ? Is there are bottleneck somewhere ?
>>> Are there any other demo's that can demonstrate an parallel speedup ???
>> You generally will only get a speed-up if you're doing sort-last
>> compositing.  In that case, each of your rendering nodes will render
>> subset of the whole scene, then the partial renderings will be combined
>> with Z or alpha compositing.  Look at the binary swap examples.
> 
> I tried the sort first and sort last examples with and the sort last
> does seem as lot faster. The binary swap seems to need the application
> code to be modified though. Is there anyway to speed up the rendering
> without modifiying the application ?

Usually not.


>> But even then, you won't get a speed-up until you reach the point at
>> which the benefit from parallelism exceeds the cost of network
>> transmission and compositing.
>>
> 
> I've done some more experiments and does appear that the network comms
> severly limit the performance (using TCP/IP over the standard NFS 
> interface at present). Is there any support in Chromium for Gig Ethernet ?

Gig ethernet works automatically, like any other ethernet speed.


> We have a Myrinet based cluster which I could try if not.

Chromium supports Myrinet/GM networks, though I have no personal 
experience with it.

-Brian


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