Will dual CPU's speed up my Phoenix FD simulations?

[ldotchopz]

Title says it all, i'm thinking of upgrading from a single i7-7820X 3.60GHz to a dual Intel Xeon Silver 12 core 2.2 GHz each.

Will i see significant simulation speed increase with dual processors, or will Phoenix FD only recognize and utilize 1 of them?

[Paul Oblomov]

Use 3960x or 3970x

[vlado]

What Paul said; a single CPU is always better for simulations.

Best regards,
Vlado

[ldotchopz]

Thanks for the response, could someone explain why that is? is it a limitation of the software or is this an overall computing problem?

[Paul Oblomov]

They have to share data between sockets. Slower, than not doing this. Simple

My cpu is 3960x - really fast. Incredibly.

[Neilg]

Dropping from 3.6 to 2.2 per core will probably slow your simulations down too.
it's a limitation of fluid simulation - everything depends on everything else at all times.

[squintnic]

yep and avoid the 32 core threadrippers as well

[Alex_M]

Um... why?

[squintnic]

super slow...will get totally outpaced by something with less cores and higher clock speed. think phoenix treats them as 2 cpus

[Alex_M]

super slow...will get totally outpaced by something with less cores and higher clock speed.

Is this conclusion based on personal experience and tests with the new Threadrippers or just a guess?

think phoenix treats them as 2 cpus

This is not true. 3970x and 3960x are treated as one CPU by Windows. I have 3970x and Windows sees it as one CPU and a single NUMA node. I agree that if you do only simulations and nothing else, then a cheap low-core count CPU is more appropriate, but if you also do rendering, IMHO there's no reason not to get a 3960x or a 3970x as they don't have the drawbacks of the old Threadrippers (multiple NUMA nodes, memory access slowdowns with Windows, lower clock speed etc.). 3970x and 3960x also boost to 4.50 Ghz in single core workloads which might sounds a bit low compared to some Intel CPUs, but don't forget that the Zen 2 architecture has 9-10% higher IPC than Intel's latest CPUs so a frequency of 4.50 Ghz on a Ryzen 3000 processors is equivalent to ~4.90 Ghz on Intel.

[squintnic]

my threadripper 2990wx 32 core is slower than my older i7 3970k in phoenix - do some tests and find out the hard way. might be different with the newer AMDs

[Alex_M]

Well, this explains it. 2990wx is based on the older Zen 1 architecture that had issues with RAM access under Windows due to the multiple NUMA nodes and because not all chips were directly connected to the memory controller. The new 3000 series Threadrippers have nothing in common with the old ones. They are made on a completely new architecture called Zen 2 which is free of all shortcomings of the previous Threadrippers - they are much faster in single core workloads, much snappier in day to day use, and maybe most importantly - they are not split into multiple NUMA nodes and don't have memory latency slowdowns because all chiplets are connected directly to the memory controller.