Discussion Forum

We’re going to try this again. About 7 months ago we put two months of effort and a lot of money into a top-of-the-line four-socket machine trying to get more speed than we were getting from a cheap single-socket i7-3930K (6 cores, 3.2 GHz, DDR3, 12MB cache, ~$600) on a large RF problem (~5000 boundaries, ~9M dofs), only to learn the hard way that COMSOL RF wasn’t able to take advantage of modern high-end computers.

We’ll probably buy at least two new computers.

For a low-budget initial experiment, I think we’ll get an i7-5960X (8 cores, 3 GHz, DDR4, 20MB cache, 64 GB max, $1060). For some problems we’ll need a lot more memory than this processor supports, but the point of this experiment is to guide us in buying a high-end machine. If it’s no faster than our current 6-core machine, it tells us that clock speed is about all that matters (notwithstanding what one sees on various COMSOL web pages). (It seems our friends at COMSOL can’t provide any benchmark data, or valid recommendations. We’re definitely not going with more than a single-socket machine. Our experience and that reported by others showed COMSOL is slower on multi-socket boards than on single-socket boards of similar clock speed. If they disagree, they should show benchmark data supporting their claims.)

For a high-end machine, I suppose we’ll go with either the E7-8891-v3 (10 cores, 2.8 GHz, DDR4, 45MB cache, ~$6900) or the E7-8890-v3 (18 cores, 2.5 GHz, DDR4, 45MB cache, $7200), depending on what we learn from the above low-budget experiment.

We’ll post what we learn. (The last time we posted what we learned, the moderator took it down immediately.) We’re hoping that maybe if we keep bugging them, they’ll eventually appreciate that they really need to figure out how to take advantage of modern high-end computers on large problems.

Yes, we do see that COMSOL RF probably does utilize additional cores effectively when it finally gets into the iterative solver, but that’s only a small fraction of the total run time, even with just 6 cores; and most of the time the engineer is sitting waiting on COMSOL (finalizing, meshing, saving, opening, …) it’s only using one core and one memory channel, no matter how many there are. (We put weeks into trying everything we were told to try to get parallelization to work, and never saw any speed up, even with distributed parametric sweeps, on a 4-socket high-end machine.)

Does anyone out there have benchmark data (or even anecdotal indications) comparing some run times and productivity experience with large problems (preferably RF or CFD) on different modern high-end computers?

David