Minimum number of CPU cores needed for the engine

[ziad-ashraf7]

I just wanted to ask , what is the bare minimum cpu cores needed with time limit settings to get some acceptable and optimized result from the engine?

I have a VPS with 2 cores, and i think that it's taking so much time on it, so is it acceptable or I'm doing something wrong ?

[fontanf]

The solver runs several algorithms in parallel, selected depending on the instance characteristics. Some of these algorithms also need to solve subproblem instances, whose resolution runs multiple algorithms in parallel too. Usually, 8 cores are enough. For irregular problems, 16 cores might be needed.

With 2 cores, the solver still works, but the algorithms share the cores, so you'll usually get worse solutions for the same running time.

How long the solver runs depends on the optimization mode:

• In the default anytime mode, the solver keeps improving its solution until the time limit, or until it proves its solution optimal, which rarely happens for irregular problems. So it is meant to be used with a time limit (--time-limit on the command line, or the time limit field in the web app). Without one, it may run for a very long time.
• In the not-anytime modes, the solver stops by itself, after a search effort that grows with the size of the instance. not-anytime-sequential uses a single thread, which may suit a 2-core machine better.

The optimization modes are described here: https://fontanf.github.io/packingsolver/optimization_modes.html

[ziad-ashraf7]

Thank you for your answer.
I just wanted to ask now another question:

Is there any way that i can enforce the solver for certain number of CPU cores to use ?
for example if I had 15 cores, does it use all of it by default or I can add a flag to it to tell him to use X number of cores?