From: Stefan Boresch (
Date: Thu Dec 12 2019 - 06:37:29 CST

Hi John,

many thanks! The environment variable does the trick!

Best regards,


On Wed, Dec 11, 2019 at 08:22:01AM -0600, John Stone wrote:
> Hi Stefan,
> The behavior of OptiX actually depends greatly on the particular
> version being used. At present VMD has no control over what OptiX does
> with its cache directory, VMD doesn't actually know about it.
> OptiX purposefully leaves the shader cache directory across runs as a
> significant performance optimization. If it is deleted, it defeats
> the entire purpose of having the cache directory in the first place.
> On some versions of OptiX, the shader recompilation runtime can be
> quite high. I've seen it reach as much as a minute for VMD in the past.
> Prior versions of OptiX placed this cache in the user's home directory,
> which was a better choice in the sort of situation you describe.
> The more recent versions behave in roughly the way you describe,
> but is complicated by the fact that not all Linux distributions
> even have a "/var/tmp" directory, and OptiX will then make some other
> choice.
> Fortunately, recent revs of OptiX that have relocated the cache directory
> also accept an environment variable that you can set that will allow you
> to override its default behavior, so that you can force the selection
> of a user-specified cache directory path:
> You should be able to set the OPTIX_CACHE_PATH environment variable
> prior to running VMD and that will cause OptiX to use the specified
> path for its cache. If you choose a directory name that is user-specific,
> this should address the conflict your students have encountered.
> Best regards,
> John Stone
> On Wed, Dec 11, 2019 at 08:59:17AM +0100, Stefan Boresch wrote:
> >
> > Hi,
> >
> > first, I tried searching the mailing list archive, but I cannot
> > get the sorted indices (by date, thread ..); only the raw messages.
> >
> > Now the real question/problem:
> >
> > I am just running a small course in which, among other
> > software, we use vmd-1.9.4a38 (Linux 64bit optix etc). When starting
> > up, the Optix Diskcache is place in /var/tmp/OptixCache, owned by
> > $USER.$GROUP and 750 permissions. This cache file never gets removed,
> > so even though user A quits vmd, logs out, a later user B when
> > staring up vmd only sees the error message that no Optix context
> > could be created.
> >
> > According to the Optix manual, the default location (under Linux)
> > for the cache should be /var/tmp/OptixCache_$USER which would
> > already solve the problem (though I'd still prefer if vmd cleaned up
> > after itself and not rely on /var/tmp being cleaned upon reboot, which,
> > fortunately, is a rare event). The manual also lists an environment
> > variable to override this, but upon a quick check this had/has no
> > effect on vmd's behavior.
> >
> > Or am I missing something (as I said I seem not to be able to
> > search/skim the mailing list archive at the moment)?
> >
> > Best,
> >
> > Stefan
> --
> NIH Center for Macromolecular Modeling and Bioinformatics
> Beckman Institute for Advanced Science and Technology
> University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
> Phone: 217-244-3349