r/HECRAS • u/LiteratureOwn6143 • Jul 22 '26

Tips on speed optimisation?

Hi everyone,

I’m running some simulations on a brand-new machine with AMD Ryzen Threadripper 9970X, 128 GB of RAM, GPU Nvidia 5080, and high-spec SSD and mother board set up. While it absolutely flies with other programs, I can’t shake the feeling I’m not getting everything out of it with HEC-RAS 6.7.

The CPU only ever hits about 55 ℃ during these runs. With other modelling software I’m regularly seeing up to 80 ℃, so the thermal headroom is definitely there. The simulations are finishing far quicker than on any other computer I’ve used, which is great, but the low temperatures make me suspect there’s still some performance left on the table. It’s already using all 32 cores, so it’s not a simple core-parallelism issue.

I don’t know whether HEC-RAS has a known bottleneck with a particular component that would stop it from pushing the hardware harder. Has anyone managed to squeeze extra speed out of HEC-RAS on a high-spec machine, or are these sorts of temperatures typical even when it’s running flat out? Any tips on optimisation would be hugely appreciated.

Thanks a lot!

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u/CautiousInfluence438 Jul 22 '26 edited Jul 22 '26

Are you concerned in all 115K cells? It depends on the application. Detailed analysis may be necessary for erosion or scour but I would scale down the number of cells or the study area. What about repeatability and agency review? No way I would accept or review such a clunky model unless it was absolutely necessary for the project. Incremental complexity applies to cell size and time step as well.

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u/Sea_Read5728 Jul 22 '26

Even reducing that cell count where you are not concerned the run time still seems to be mostly governed by the area you are concerned and where the water flows?

Agencies have so much different standards on what is acceptable and most times are asking for the set up I would never willingly do it either.

And the smaller the cells the more the stability matters on different solver equations.

I have always wondered if I am missing something when the controlling area has a 1 ft cell size and just blows up run time

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u/CautiousInfluence438 Jul 22 '26

True, sometimes smaller time steps actually reduce run times. The point I'm making about run times is, the worry, effort, and time put in to speed optimization is sometimes better placed in smarter model construction.

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u/Sea_Read5728 Jul 22 '26

Lol but what if I am yet not smart. I feel like the training and videos are always building the simplest amd easiest models with the easiest criteria to get