[smashy1985]

Hi everyone,
recently we changed the workstation where we are using Star CCM+ and other softwares for 2D and 3D modeling in the office of naval architecture I am working for.

The previous workstation was configured as follows:

- CPU Intel i7-4770K (Quad Core – 3,5/3,9 GHz – Cache 8 MB – HyperThreading)
- 16 GB Ram Dual Channel DDR3 12800 – 1600 MHz (2 x 8 GB)
- Motherboard GIGABYTE – Chipset Intel Z87
- SSD 240 GB + Hard Disk 1 TB
- Graphic Card ASUS GTX 650 – 2 GB GDDR5

While the new one is configured as follows:

- CPU Intel i9-9940X (14 core – 3,3/4,4 GHz – Cache 19,25 MB – HyperThreading)
- 64 GB Ram Quad Channel DDR4 – 2666 MHz (4 x 16 GB)
- Motherboard ASUS WS X299 Pro – Chipset Intel X299
- SSD NVMe 250 GB + Hard Disk 2 TB
- Graphic Card ASUS GTX 1660 Super – 6 GB GDDR6

After instaling the software on the new worstation, using the same licence that allowed us to make parallel simulations, we noticed that the new P.C. is slower than the previous one.

Just two examples:
- #1 : Test simulation (2D External Flow around a Cylinder – 22.000 Cells) started with 6 parallel processes on the same host.
The previous PC processed about 6000 interations in 5 minutes, while the new PC process about 1200 iterations in the same period of time.
- #2 : Simulation “Marine Resistance Prediction: KCS Hull with a Rudder” (Star CCM+ Tutorial – 530.000 Cells) started on the new workstation in Serial mode and in parallel mode with 6 processes on the same host. On both modes, the new workstation calculates the same number of iterations in the same period of time.

According to these examples, I can see that there may be a problem linked to the simulation in parallel mode on the new PC.

Does anyone have an idea in order to solve this issue?

Many thanks for your help.

[ashokac7]

First check single core speeds of both the system for same simulation.

(like time taken for 100 iterations)

If they are comparable then you can conclude that there is problem with parallelization.

Few additional checks includes-

1. check if you have populated right memory slots for RAM (quad channel)
2. for 6 processor, speed should be somewhat similar for both the configuration.


Some snaps for parallel set up commands would suffice.

[cwl]

I'd start with very primitive and obvious things:
- does the CPU load (w.r.t. to Star threads to Cores count, i.e. wouldn't be 100%) look correct?
- are there 6 (equal to parallel threads specified) processes launched by Star?

[smashy1985]

Hi everybody,

first of all, I would like to thank you for your prompt reply.

I followed your advices and I make some tests. I will reply you in order.

According to the suggestion of ASHOKAC7, I tried to run the same simulation (Test simulation - 2D External Flow around a Cylinder – 22.000 Cells) on both workstations on serial mode and here you can find their results:

-Old PC : about 11 seconds to elaborate 100 iterations (2620 iterations in 5 minutes)
-New PC : about 24 seconds to elaborate 100 iterations (1250 iterations in 5 minutes)

Instead, considering the RAM memory instalation into the slots of Mother Board, we just followed the procedures described in its owner manual (I hereby attach the photo of the installed RAM modules - photo1).
Photo 1.jpg

With reference to the question of CWL, after having looked to Windows task manager on the new workstation, everything seems to be correct. I can show you the screenshot of the task manager when the PC is running the test simulation in serial mode (photo 2) and in parallel mode with 6 parallel processes on local host (photo 3).

Photo 2.jpg

Photo 3.jpg


According to your opinion, which could be the problem? May it be an hardware or a software issue?

As you can see from the attached photos of task manager, I already disabled the INTEL hyperthreading on the new PC, as suggested on the software manual.

Many thanks again for your support.

[ashokac7]

RAM configuration does look OKAY.

Can you test your PC on Userbenchmark.com to check whether each hardware component is working properly.
Search for under performing component.
If Hardware is not the issue, then you can focus to software side.
Like testing parallel simulation on some other software, like Ansys. (or OpenFOAM).

CPU usage for 6 processes (photo-3) does look exceptionally high. For 6 processing cores, out of 14, CPU usage should be around 40%, isn't it?
Do some benchmark, like Userbenchmark or CPUZ benchmark. There you can also check what performance is achieved by other users for same processor.

[smashy1985]

Hi ashokac7,

I tried both PCs using userbenchmark.com, as per you suggestion.

I tested the new workstation with two different setting for the RAM :

- X.M.P. Disabled
- X.M.P. Enabled ( Profile #1 - DDR 2666 13-15-15-35 - 1.350V )

The picture attached (image #1 and image #2) can show you the results of both tests.

Image_1.jpg
Image_2.jpg

It seems there is a problem with the RAM memory that has a very low bench percentage (under 10%) on both tests, reporting also an alert message.

Remaining parts seems to work correctly.

Instead, the test on the old PC gives a good results for RAM memory ( about 60% as shown on the image below).

Image_3.jpg

Do you believe this is causing the slowness of the simulation on the new workstation?

[bluebase]

Hi smashy,

it seems your ram (or its configuration) is indeed the problem.
The memory bandwidth could have been up to approx 80GB/s according to your cpu. But you only have 2GB/s in your current setup. Your old pc has 25GB/s bandwidth.

And as most know, currently memory bandwidth is the bottleneck for CFD run speed.

So, your search should focus on topics around that. There must be something wrong with the memory, its setup, or some malicious bios setup.

Could you check the product id, wether all your dimms are from the same batch?
check wether the respecitive products are found in the recommendation list: https://dlcdnets.asus.com/pub/ASUS/m...L_20191212.pdf
And whether they support 4 dimms according to that list.

Make sure your bios is updated, download the compatible version for your cpu under "cpu & memory" https://www.asus.com/Motherboards/WS.../HelpDesk_CPU/

Edit:

You might use the tool cpu-z from https://www.cpuid.com/softwares/cpu-z.html
to inspect your memory setup.

In the tab memory and spd you could compare the timings and modes with the expected setup.

[LuckyTran]

RAM on new PC is indeed performing way below expectations. The throughput should be 4x-8x faster. Run cpu-z or HW monitor and figure out what's going on. If RAM or motherboard is not outright defective, fixing it probably requires a trip into the Bios.

If there is a defective stick then you can try installing only a single stick or test them in pairs of 2 (instead of plugging in all 4) and turning on the PC to see what happens. Also try moving them from the 4 gray slots to the 4 block slots.


And this is now no longer a Star-CCM issue but a general hardware issue.

[smashy1985]

Dear All,

I'm happy to inform you that, thanks to your advices and help, I found out the issue (bug in the Bios version installed on the motherboard).

Now everything is working correctly and better than the previous workstation.

Many thanks for your support.