From: John Stone (
Date: Tue Jul 10 2007 - 20:26:32 CDT

  Multiple CPUs won't help much for improving the interactive
rendering speed of multi-million atom systems, since the GPU does
all of the hard work. If the interactive display rate is the
limiting factor for your performance, you should pick up a
more powerful graphics card first since that will make the biggest
difference for your performance.

  John Stone

On Mon, Jul 09, 2007 at 03:12:00PM -0400, Axel Kohlmeyer wrote:
> On Mon, 9 Jul 2007, SeongJun Heo wrote:
> SJH> Recently, I tried to display multi-million atoms system on Linux using 2
> SJH> core-2-duo CPUs with 8GB ram. But I found VMD uses just one CPU. How can I
> SJH> make VMD use multiple CPUs?
> actually VMD _does_ use multiple CPUs, but only for some tasks
> and using multithreading (so watch out for the VMD process using
> more than 100% CPU). the current version 1.8.6 has some more
> multithreading than the previous ones, but there are many more
> areas, where multi-threading could be applied (e.g. several measure
> subcommands etc.).
> please note that the graphics/GUI _have_ to be in a single thread
> and also the script interpreters are non-threadable.
> on a desktop machine you can benefit a bit from your dual-core setup
> by having the Xserver and VMD running on different cores...
> but other than that, there is little you can do except
> adding more multi-threading to the existing functionality.
> the reduced performance of the multi-million atom system
> is most likely due to the limitations of your graphics
> subsystem. for OpenGL and particularly GLSL this is murder
> even for the most capable cards.
> even though i have a pretty capable card in my desktop and twice
> the cpu power and memory in my desktop, for multi-million atom
> systems, i am mostly using either the lines representation
> (with linewidth set to 2) or the points rep (with pointsize set
> to 6 or larger).
> cheers,
> axel.
> --
> =======================================================================
> Axel Kohlmeyer
> Center for Molecular Modeling -- University of Pennsylvania
> Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
> tel: 1-215-898-1582, fax: 1-215-573-6233, office-tel: 1-215-898-5425
> =======================================================================
> If you make something idiot-proof, the universe creates a better idiot.

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