Hi Dan,

Thank you for your response.

By "start of the simulation," I’m referring to the point where the timestep 
is already running. As for the profiler, I can use the built-in tools in 
Microsoft Visual Studio 2022 on my laptop. However, the issue mainly arises 
towards the end of the simulation, and the last time I ran it on the 
workstation, it took about 4 days to complete. I could try running it for a 
few hours to see if the problem starts to manifest earlier.

One other thought I had is that the slowdown could be related to saving 
around 20 functions for post-processing and plotting with GNU plot at the 
end. Do you think that this could be a contributing factor?

The reason I’m using MCORE instead of DEM-E is because there’s already 
someone else in the project working on creating a particle bed using DEM-E. 
Instead, my thesis focus is on the vehicle itself, and since we also need 
to build a prototype, I’m using the previous terrain model (built with 
MCORE) to generate initial results while waiting for the DEM-E model to be 
ready.

Thank you again.

Gianni

Il giorno martedì 24 settembre 2024 alle 18:47:05 UTC+2 Dan Negrut ha 
scritto:

> Gianni – it might be that the initial process is associated with setting 
> up the simulation.
>
> When you say “start of the simulation”, do you mean the simulation time is 
> advancing, or are you referring to the “set up” stage, when there is no 
> time integration yet. It might be that memory operations are so 
> overwhelming that the CPU is stalled most of the time waiting for data to 
> move back and forth between CPU and RAM. This is a guess, and if you have 
> 30 mins and get to the bottom of it, it’d be interesting to run a profiler 
> on the code, to see where the time is spent during the dynamics simulation.
>
>  
>
> One more question: is there a good reason you want to use MCORE? In case 
> you need friction and contact on a large scale, you might take a look at 
> Chrono DEM Engine.
>
>  
>
> Dan
>
> ---------------------------------------------
>
> Bernard A. and Frances M. Weideman Professor
>
> NVIDIA CUDA Fellow
>
> Department of Mechanical Engineering
>
> Department of Computer Science
>
> University of Wisconsin - Madison
>
> 4150ME, 1513 University Avenue
>
> Madison, WI 53706-1572
>
> 608 772 0914 <(608)%20772-0914>
>
> http://sbel.wisc.edu/
>
> http://projectchrono.org/ 
>
> ---------------------------------------------
>
>  
>
> *From:* projec...@googlegroups.com <projec...@googlegroups.com> *On 
> Behalf Of *Gianni Curti
> *Sent:* Tuesday, September 24, 2024 5:33 AM
> *To:* ProjectChrono <projec...@googlegroups.com>
> *Subject:* [chrono] Percentage of CPU decrease over time
>
>  
>
> Hi everyone,
>
> I’m encountering some issues with Chrono::Multicore in my simulation, 
> which is based on the demo_MCORE_Cratering example. The goal is to simulate 
> the interaction of an object with a particle bed at rest. The code compiles 
> and runs without errors, but I’ve noticed an unexpected drop in CPU 
> utilization.
>
> At the start of the simulation, all the threads I allocate are working at 
> 80-90% capacity. However, as the simulation progresses, their utilization 
> gradually drops to around 10% or even lower. I had expected the 
> computational load to increase as the number of contacts grows from about 
> 7,000 to 50,000, but this CPU behavior is quite strange.
>
> I’ve observed this issue on both my Windows laptop (with 20 threads) and a 
> university workstation running Linux (with 40 threads). Has anyone else 
> experienced this? Could it be that the nature of the problem makes 
> parallelization progressively more difficult as the simulation advances?
>
> Thanks in advance for your help!
>
> Best regards,
> Gianni
>
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