I was wondering if someone has done a study of efficacy of CPUs. I am grateful to have 24 cores, and it seems like using all 24 is about the same speed as using 20, for example. Is there a upper bound above which diminishing returns are seen in the 100k nodes (plate model) size range?
Femap is mostly single threaded, so won't take much advantage of multi-core today, although that may change in the future. NX Nastran can take advantage of many cores if you set that up. But it is very solution dependent. Frequency response scales very well with number of CPU's. Linear statics is good up to somewhere around 4-8 cores. NX Nastran likes high speed bandwidth, so setting up the scratch drive with an SSD, or even better, a PCIe based SSD can have a huge effect on NX Nastran performance.
We have recently purchased a new 20 core machine, and I can report the following brief summary:
For Advanced Non-linear explicit simulation (30k nodes), maximum performance was reached using 4 cores. There was a performance penalty when increasing the core count beyond 8.
I also ran some other test models using a 230k nodes dense cube analysis (still using the standard SOL101 sparse solver, even though iterative is much better for this specific matrix style). The optimum core count was around 8. Performance improvements were still occuring all the way up to 20 cores, however, the percent advatange above 8 cores was not enough to justify using the extra cores for so little benefit.
Using GPU with an nvidia K4200 provides a performance penalty (for such a dense matrix example), so I switched that off.
All of the test analyses ran entirely in memory, including sizeable SMEM, and all scratch set to a ramdisk.
My conclusion was that if I want the best productivity for a single user machine, I would choose a computer with a single cpu of 4 physical cores, with the fastest GHz rating. Probably an Intel i7-4790K (4.0GHz). This provides the best combination of Femap modelling performance (this cpu has excellent single thread rating), plus sufficient cores to run standard and advanced non-linear solvers at optimum parallelisation, without spending a fortune on the cpu & computer. Even though our machines here are all Dell Precision dual cpu with numerous cores, the multi-threading advantages are not big enough beyond 4 cores to make buying that style of computer worthwhile for an individual using Femap.
This means that the optimum Femap with NX Nastran single user computer looks more like a top-end gaming machine than an engineering workstation. Save money on the dual cpu architecture and premium Xeon cpus and spend it on memory, graphics and (preferably PCI) SSD's.
On running multiple jobs, each with multiple cores, keep in mind you will very soon saturate the memory bandwidth on a standard workstation, which will slow down the NX Nastran performance. Fast memory and I/O Bandwidth is key to good NX Nastran solve times.