How can I determine the number of processor?

[Wangyun]

Dear STKO team
In our lab, there two workstations.
one: 32 cores and 32 logical processors
another one: 20 cores and 40 logical processors
How can I determine the number of partition when I use parallel calculating?
What determines it? Cores or logical processors?
Thank you

[STKO Team]

You can use at most the number of logical processors.
However, it also depends on the size of the model. If your model is small, using a lot of processors can also slow down the analysis time

[Wangyun]

How many elements should exist at every processor when it has a high efficiency?
Thank you

[STKO Team]

4 to 7 thousands

[BuuNguyen]

Is it possible if i devide 2000 to 3000 elements per processor?

Now, its around 4000 to 5000 elements per processor. but my CPU just reaches 50 60% of capacity.
Buu

[STKO Team]

Yes, do it and try whether you have performance gains or losses... sometimes if you use too many processors it may slow down instead of speed up

[Charon]

Dear STKO Team,

Hi,I have some questions.

1.Now, a year later, have you changed your proposal for the number of cores corresponding to elements and OpenSees mp?

2.My model was previously able to compute with 48 or even 72 cores, however, in the last few days I found that I can only use up to 24 cores and no more, why? I think this slows down the computation and my workstation has a lot of free resources to be wasted. I have attached my model file below.

Best wishes,
Charon

[STKO Team]

It's crashing if you use too many processors because you are using model subsets. And if you use too many processors, during the first stage, when the superstructure is not preset yet, some processors will be completely empty.

If it was working before, probably empty processors were allowed before (in OpenSees) but not now. We will look into it, but it's in OpenSees, not in STKO.

However, there are some workarounds:
Instead of adding new parts during the analysis, you can add everything at the beginning (but not the interactions that connect the 2 parts).
Let's do an example:
Say you have 2 geometries and 1 interaction that connects them:

• SOIL
• STRUCT
• CONTACT (interaction)

You can do this:

• Add model subset (SOIL+STRUCT). Since the interaction does not generate nodes, now all nodes are in OpenSees, and all processors are full
• Fix the STRUCT in ALL DOFS and all NODES (it's not connected to the soil, so it will be singular if you leave them there)
• Run first analysis
• Remove the Fix in STRUCT and add modelSUbset with CONTACT