[Yining CHEN]

Hello everyone!
I am new here and this is my first post on this forum.

I am using Ansys 19 with a new computer.

CPU：AMD Ryzen TR 1920X (only one cpu)
12 Cores, 24 Threads, basic clock 3.5GHz
MB：X399 Zenith Extreme
Memory：16G*2 DDR4-2400 HyperX FURY (total 32G)
Graphics card：EVGA GTX1060 3GB
SSD：Samsung 512G
windows 10 Pro 64bit


My question is that the simulation in CFX-solver is really slow.

And there is my simulation mesh statistics

Number of Nodes: 2377481
Number of Elements: 3906558
with MultiPhase flow Simulation

Enabled Double Precision without the large problem.

Intel MPI local Parallel with 12 Partitions.

Partition Type is Recursive Coordinate Bisection.


I am wondering that AMD cpu is not a suitable CPU for CFX(even Ansys).

Does anyone have the same problem? or any advise?

Thank you so much.

[ghorrocks]

The speed of CFX follows the CPU2017 floating point benchmarks (http://spec.org/cpu2017/results/) very closely. There is nothing in the Ryzen which makes it "bad" with CFX. You should be able to estimate your expected results in comparison to other CPUs from the CPU2017 lists.

Make sure you have checked:
* Your motherboard is suitable quality
* Your BIOS is up to date (old BIOS does not support the most recent chips and defaults to a very slow mode.)
* Make sure your BIOS supports your CPU
* Check all your other drivers are up to date (HDD, network etc)
* Check you don't have a background task throttling your computer, antivirus is a key culprit here.
* Check that other users are not running background tasks
* Run a benchmark on your system and check you get the expected speed

If all that checks out then it could be something with your model. That is a whole different question we will talk about if you can confirm you workstation is OK for these basic checks.

[FrankW]

Hi,

you have to use all ram channels otherwise your system will be slowed down. In your case you need 4 ram modules. More information can you find at:


https://www.cfd-online.com/Forums/hardware/

[Yining CHEN]

Thank you so much,ghorrocks!

Thanks for your detail illustration and description.
I will check the driver and BIOS again.

Because I have checked a lot of computer setting, I am sure that I don't have any antivirus or other background tasks...

I am still trying to figure out some problems with my workstation.

Thanks for your reply.

[Yining CHEN]

Hi, FrankW!

It seems like I post the wrong forums...

Also thanks for your reply.

But I am not quite sure about the "4 ram modules"...
It means that the ram doesn't enough for CFX?
or I should change some settings?

Could you tell me more about it?

Thank you so much!!

[FrankW]

Hi Yining CHEN,

the ram size is enough for your case. The problem (bottleneck) is the communication between the cpu and the ram. You can try it out, use 1-12 cpu cores and if you look at the results it should show a linear behavior up to approx. 6 cores.

[Yining CHEN]

I found that my memory is Dual channel, but this AMD 1920x CPU can support Quad Channel Memory.

I am still not sure about whether it will affect the simulation speed.......

Thanks for ghorrocks and FrankW's reply.

[FrankW]

Originally Posted by Yining CHEN

I found that my memory is Dual channel, but this AMD 1920x CPU can support Quad Channel Memory.

Look at the manual of your motherboard (chapter 1.1.4.). And yes, if you use only 2 memory modules you have dual channel support and when you use 4 memory modules (on the 4 different channels of your MB) you can get quad channel support.

[Yining CHEN]

Dear FrankW
Thank you so much for your reply!!

But I have another question about "the memory frequency", as you said before the ram size is enough but I am wondering that the frequency of the memory will also affect the simulation speed or not.

Right now I am considering to buy another 16G memory or buy 4 Quad high frequency memory.

[FrankW]

Hi Yining CHEN,
in the simplest case you buy 2 identical modules as you already have. Yes, higher memory speed can speedup your simulation, but it depends many things. That's why I'm not going to give any advice on this either.

@ghorrocks
Can you move the thread to the hardware section? I think he fits better there.

[ghorrocks]

You should always check a new workstation against benchmark results (such as spec.org) to check that you are getting the correct speed.

Many times I have found things like out of date BIOS, incompatible memory or old drivers are crippling a new workstation. So you need to do a benchmark to find if you are getting the speed you paid for.

Good point, I will move this thread to the hardware forum.

[evcelica]

As others have stated, you need 4 RAM modules to use all 4 of your memory channels. Since with 12 threads @ 4 GHz, you will be completely memory bandwidth limited, going to 4 RAM DIMMs will double your simulation speed vs. using only 2 DIMMs.

Be sure to populate them properly, read your motherboard manual. Usually it is the non-black colored slots you should populate first (grey in your case, but check your manual to be sure).
This video has a lot of good info on Memory configurations, and mixing different kits.
https://www.youtube.com/watch?v=-D8fhsXqq4o

[Ivanrips]

Originally Posted by Yining CHEN

Hello everyone!
I am new here and this is my first post on this forum.

I am using Ansys 19 with a new computer.

CPU：AMD Ryzen TR 1920X (only one cpu)
12 Cores, 24 Threads, basic clock 3.5GHz
MB：X399 Zenith Extreme
Memory：16G*2 DDR4-2400 HyperX FURY (total 32G)
Graphics card：EVGA GTX1060 3GB
SSD：Samsung 512G
windows 10 Pro 64bit


My question is that the simulation in CFX-solver is really slow.

And there is my simulation mesh statistics

Number of Nodes: 2377481
Number of Elements: 3906558
with MultiPhase flow Simulation

Enabled Double Precision without the large problem.

Intel MPI local Parallel with 12 Partitions.

Partition Type is Recursive Coordinate Bisection.


I am wondering that AMD cpu is not a suitable CPU for CFX(even Ansys).

Does anyone have the same problem? or any advise?

Thank you so much.

Hi friend;
I share a picture about benchmark using several processors for CFD.
stars.png

[Yining CHEN]

Hello Everyone!!
Sorry for the late reply, also I am appreciated everyone's reply!!

Right now I changed all memory to 4 channels Memory!
The simulation speed has been faster!!

@ghorrocks and @FrankW Thanks for helping me move this thread to the hardware section.
By the way, I run the benchmark and the result is good.

@evcelica Thanks for sharing that memory video!! It helps me a lot!!

@Ivanrips It seems that the highest performance with the highest price......

[Yining CHEN]

Right now I have met another problem......

There is a function called "NUMA" in this AMD CPU.

I am wondering that if the "NUMA" will also affect the CFX simulation speed or not.

Thanks for your attention.

[flotus1]

You need to keep NUMA enabled, otherwise you are back at the speed you had with only 2 DIMMs. CFX is a NUMA-aware program.
Your CPU has two dies enabled, each with its own memory controller and thus its own NUMA domain. Reverting to UMA would increase memory latency and decrease bandwidth for NUMA-aware applications.

[Yining CHEN]

Thanks for your reply.

To activate NUMA mode, do I need to change any settings for CFX?

[flotus1]

NUMA is a hardware setting. You can only change it in the bios. CFX with default settings should work just fine.