22 August 2022

AMD Ryzen 9 5950X may NOT be as fast for CFD as I otherwise thought/hoped

So this test is based on the same testcase, but just testing it with two different CFD applications.


Both are steady-state solutions (which is normally used to initialise the flow field for the transient solution, which I am not testing at the moment).


The AMD Ryzen 9 5950X cluster is two nodes, where each node has an AMD Ryzen 9 5950X (16-cores, SMT disabled), 128 GB of DDR4-3200 unbuffered, non-ECC RAM, and a Mellanox ConnectX-4 MCX456A-ECAT 100 Gbps Infiniband network card whilst the Xeon cluster is two nodes, each with dual Intel Xeon E5-2690 (V1, 8-cores each, HTT disabled for both processors), 128 GB of DDR3-1866 2Rx4 Registered ECC RAM running at DDR3-1600 speeds.


In one of the applications, the AMD Ryzen 9 5950X finishes the solution in 23342.021 seconds whilst the Xeon pair of nodes finishes the same steady state solution in 15834.675 seconds (or about a 32.16% reduction in wall clock time), which is rather significant. This run has about 13.4 million cells and it takes this long because it is running for 1000 iterations.


And then in another, different CFD application, but also running the steady-state solution run for 48 iterations, and finishes the solution on the AMD system in 292.665 seconds whilst on the Xeon system, it finishes this solution in 264.48 seconds or about 9.63% faster.


That's really interesting that the AMD Ryzen 9 system, despite it being 8 and a half years newer, still isn't able to be as fast as an older Xeon-based cluster.


The only real upside to using the Ryzen-based system over the Xeon based system -- well, two things actually are:


1) The Ryzen based system uses quite a lot less power compared to the Xeon cluster. It isn't surprising that I can see power consumptions, under load, of upwards or around 1 kW for just running two nodes (and running all four nodes pushes that total up to somewhere between 1.6-1.9 kW) whereas the Ryzen based systems combined, is using probably only about maybe 400 W total.


2) The Ryzen based system is a LOT quieter than the Xeon Supermicro Twin Pro^2 server (6027TR-HTRF). 

 

So, if you're running it in a home lab environment where you don't live by yourself, then despite it being slower, it might still be a better alternative for these two reasons.


And the Ryzen based solution is certainly cheaper than the Threadripper, Threadripper Pro, and/or AMD EPYC solution platforms, where you might be able to get some of that performance back, but I can't say for certain without actually testing it myself because I thought that having the 16 faster clock speed cores on the Ryzen 9 5950X would be faster than the Xeon E5-2690 platform. Based on the data and the results, I stand corrected.


I did not expect that.