Summary

We have implemented a method of running the AVS/Express user interface on the login nodes while performing parallel module processing and rendering on the backend nodes. Minimal changes to the AVS source code have been made by allowing the express process to make MPI function calls from the login node. This is done by forwarding those calls to a proxy rank 0 process running on the backend nodes. Communication between the various AVS/Express processes via the proxy is transparent to those processes. While there is some performance reduction associated with this mechanism, the reduction is not critical for an interactive application and not so great that the application becomes uninteractive.

The need to forward the X11 user interface over the ssh connection to HECToR is another performance reducing factor. It would be possible to run the express process on the user's local desktop (as a client) provided an ssh tunnel could be established from the HECToR login node to the user's desktop. The MPI proxy process could then have its connection to the login node tunnelled to express running on the user's desktop. This would be more efficient than forwarding the X11 connection from the login node. However, such connections are not permitted on HECToR.