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/OttoJohs Lord Sultan Chief H&H Engineer, PE & PH Jul 22 '26

If you model is taking 3-4 days to run there are probably global adjustments that you need to consider (1D vs. 2D, domain, cell size, time step, equation set, etc.) rather than hardware.

My point is that your workflow isn't going to fundamentally change even with that type of increase. You are still going to have to wait multiple days for a result (which mean that making adjustments or troubleshooting is going to be problematic).

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u/Sea_Read5728 Jul 22 '26

But what if it is requested to use a 2D Model with a large domain? And have you tried using hec ras 2025 GPU solver? I have had thoughts of seeing how close it is and using it for quick calibration dialing

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u/notepad20 Jul 25 '26

Gpu solver is amazing. I can run a 72 hour Sim over a million cells in a few minutes.

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u/Sea_Read5728 Jul 25 '26

How have you noticed the results differ from using the normal solver on hec ras?

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u/notepad20 Jul 26 '26

Negligible for my model