[iamrahul]

hello everyone


I would be deeply grateful if you can lend your expertise on my dilemma :


OBJECTIVE


Ansys Forte for diesel sector mesh- 50K mesh cells maximum on adaptive mesh settings. Chemistry-200 species.


Which should i aim:


A 3950X build or the x299 platform. What memory size and speed should be considered and which GPU to have mainly for post processing. We will not be doing any gaming.


Also will it be prudent to invest a in a clevo barebone with i7- 9700 with 32 gb 2666 Mhz RTX 2060 for such small mesh sizes? (though chemistry time scales could be a major factor)


I know that dual channel ram might be a constraining factor for the 3950x and 9700 cpus, but considering the low mesh sizes would it matter significantly?


Any other issues -please feel free to comment and suggest


Regards

[flotus1]

Disclaimer: I never used Ansys forte, and never saw any benchmark for it.
So how many threads does your license allow you to run?

I know that dual channel ram might be a constraining factor for the 3950x and 9700 cpus, but considering the low mesh sizes would it matter significantly?

If the model does not fit into last level cache, memory matters. While 50k cells might seem small, I would assume that it still won't fit into L3 with a commercial CFD solver. Especially not when considering the additional memory requirement for the chemistry models.

I highly doubt that a Ryzen 3950X would give you any benefit over a Ryzen 3900X. They have the same topology and same amount of cache. 16 cores would just be starved for memory bandwidth.

I would probably go for a mid-tier X299 CPU with 8-10 cores, and some really fast memory. You could try asking Ansys Support, maybe they surprise you with a helpful answer.

For the GPU: according to this document, Forte does not have any kind of GPU acceleration.
So any cheap graphics card released over the past 5 years should do. Maybe don't go lower than 2GB of GDDR5.

I further assume you will be doing transient simulations with lots of time steps. In case you want to save them frequently for post-processing, an NVMe-SSD seems like a good investment.

[iamrahul]

thank you so much for taking your time out to help. License core max=16
so as i perceive going to a x299 platform would be a prudent choice with minimal investment in GPU (>2 gb ddr5) and nvme.



So if i propose a desktop build of:


i9 9960x
64 gb 3200 ddr4
1050ti
512 gb nvme


will it be ok?
Also as we would need an mobile platform for interim needs ,will the i7 9700 32 gb 512gb nvme be of any help atm till we get to build the desktop?



I thank you again for your kind reply
regards

[flotus1]

If you are not buying the PC right away, then get a 10th gen CPU. They will be released by the end of November, and will cost the same as the current gen.
"Fast" RAM for this platform starts at DDR4-3600. You won't need 64GB, but buying 16GB DIMMs is an easy way to have guaranteed dual-rank.

Trying your simulations beforehand on any other PC could help you determine what kind of hardware is actually worth it. For example, you could run a scaling test. See how the speedup is going from 1->2->4->6...cores. Knowing the specs of this machine, we could then make a better prediction which setup is worth your money.

Sure, you can get a laptop with an I7-9700, if you don't have anything to run your simulations right now. Maybe you could use that system to run a few tests.

[iamrahul]

Originally Posted by flotus1

If you are not buying the PC right away, then get a 10th gen CPU. They will be released by the end of November, and will cost the same as the current gen.
"Fast" RAM for this platform starts at DDR4-3600. You won't need 64GB, but buying 16GB DIMMs is an easy way to have guaranteed dual-rank.

Trying your simulations beforehand on any other PC could help you determine what kind of hardware is actually worth it. For example, you could run a scaling test. See how the speedup is going from 1->2->4->6...cores. Knowing the specs of this machine, we could then make a better prediction which setup is worth your money.

Sure, you can get a laptop with an I7-9700, if you don't have anything to run your simulations right now. Maybe you could use that system to run a few tests.

Thank you again and especially for the deep insight that you gave me. Thank you.
I will wait for the 10th gen. here in India every PC part is so unjustly expensive. Can i ask you the favour to detail me a rig configuration as you would deem fit for me? You outlined that "You won't need 64GB, but buying 16GB DIMMs is an easy way to have guaranteed dual-rank."- can you please explain especially the " dual rank" thing. Also since the x299 motherboards have 8 dimm slots, do i need to populate all the dimms? Should i target 16*2?
thank you so much for your observations.

[flotus1]

https://www.crucial.com/usa/en/what-is-a-memory-rank
You don't have to read all of that
One relevant difference is performance. With 1 rank per channel, you get less bandwidth at the same memory frequency. So you would need even faster RAM to make up for the difference.
What you should be aiming for on X299 is 4 DIMMs populated.

I can't really give you a full list of recommended components. Well I could, but it would not make much sense, since we live in different parts of the world. I don't know which parts are available in India, or what they cost.
And more importantly, I would like to encourage you once more to run some scaling tests, before buying an expensive new system. Get back with the results and as much information about CPU and memory configuration of the test system.

[iamrahul]

Originally Posted by flotus1

https://www.crucial.com/usa/en/what-is-a-memory-rank
You don't have to read all of that
One relevant difference is performance. With 1 rank per channel, you get less bandwidth at the same memory frequency. So you would need even faster RAM to make up for the difference.
What you should be aiming for on X299 is 4 DIMMs populated.

I can't really give you a full list of recommended components. Well I could, but it would not make much sense, since we live in different parts of the world. I don't know which parts are available in India, or what they cost.
And more importantly, I would like to encourage you once more to run some scaling tests, before buying an expensive new system. Get back with the results and as much information about CPU and memory configuration of the test system.

Thank you so much. I will get back with the tests as soon as we can land the laptop.
regards

[iamrahul]

Sir,


i am attaching an initial forte run summary on i5 laptop for your kind consideration and further advice. This was an initial run some months ago on 3 logical cores hyper-thread enabled and 8gb ram.(dell inspiron)


thank you ever so much