Re: [Chromium-users] no parallel speed up ?

[Smith, I. <I.C...@li...>]

> -----Original Message-----
> From: Brian Paul [mailto:bri...@tu...]
> Sent: 06 February 2008 02:25
> To: Smith, Ian
> Cc: chr...@li...
> 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 ?

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

many thanks,

-ian.