constraint programming

[maamani10]

hi and tnx for great project. can u explain if our model have multiple constraint and objective function how we can implement it and use Jmetalpy?

[AndreasH96]

Hi,

I don't know if this will be helpful but I'm currently using JmetalPy for my masters project. I'm solving a vehicle routing problem and I'm implementing the constraints through simply increasing the cost with a large value if the constraint is not met. This makes the algorithm deny the solution. I guess this is somewhat of a workaround but it seems to work for now.

Here is an example, I have a list of lists named paths and I've got a set of nodes callet permutation. This constraint checks so that all the nodes are visited by some path.

if not self.__allVisited(permutation,paths):
       fitness += 10e10 

solution.objectives[0]  = fitness

In my case I want to minimize the cost, if you would want to maximize a fitness value I guess you could subtract a large number instead.

If someone has a better solution for this I would appreciate it, but this seems to be working for now as I said.

[ajnebro]

The constraing handling mechanism used in jMetalPy is the same used in jMetal, which is described here: https://jmetal.readthedocs.io/en/latest/constraints.html

[AndreasH96]

Thank you @ajnebro !