From: John Stone (
Date: Wed Jun 10 2020 - 10:05:54 CDT

  I haven't had the GPU run out of memory, but I've been observing an
unexplained performance loss anomaly with a simple movie rendering
test that just renders a virus scene in a tight loop a few hundred
times. I haven't seen GPU memory use climb noticably in my test, but
I will keep an eye out for this.

If I understood your symptoms, you encounter the problem when RTX is
enabled, but NOT if RTX is disabled?

What happens if you set this environment variable before you run VMD:


On Wed, Jun 10, 2020 at 03:05:10PM +0200, Bart Bruininks wrote:
> Dear VMDers,
> I am using the 1.9.4a42 build to render videos of trajectories on a
> server. There used to be the issues that after a while frames would not be
> written anymore. However, atm it seems all frames are written, but the
> internal rendering data structures are not cleaned rendering between
> frames. This causes my VRAM to get filled during successive renders and
> eventually my GPUs kill themselves crashing VMD and sometimes taking some
> other stuff with them (window manager etc.). I can understand that having
> no free VRAM could result in such issues, but I guess it shouldn't build
> up like that in the first place.
> VMD:
> 1.9.4a42
> Nvidia Drivers:
> NVIDIA-SMI 440.82 Driver Version: 440.82 CUDA Version: 10.2
> GPU's:
> OptiXRenderer) Creating OptiX window: 672 x 805..
> OptiXRenderer) VMD TachyonL-OptiX Interactive Ray Tracer help:
> OptiXRenderer) ===============================================
> OptiXRenderer) Using 2 devices:
> OptiXRenderer) [0] Quadro RTX 8000 CUDA[0], 47.5GB RAM, KTO
> OptiXRenderer) [1] Quadro RTX 8000 CUDA[1], 47.5GB RAM
> Cheers,
> Bart

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