Can I use ExprCons for model.addConsNode()?

[purin0604]

Hi,

I would like to add some constraints locally using model.addConsNode().
(Set some variables to be zero. )
From coloring examples and documents, I learned it should be something like:

Class myConshdlr(Conshdlr):

    def consprop(self, constraints, nusefulconss, nmarkedconss, proptiming):
         for var in self.model.vars:      
               if condition is True:
                  self.model.chgVarUb(var, 0.0)
        return {"result": SCIP_RESULT.DIDNOTFIND}

    # fundamental callbacks 
    def consenfolp(self, constraints, nusefulconss, solinfeasible):
        return {"result": SCIP_RESULT.FEASIBLE}
    def conscheck(self, constraints, solution, checkintegrality, checklprows, printreason):
        return {"result": SCIP_RESULT.FEASIBLE}
    def conslock(self, constraint, nlockspos, nlocksneg):
        return {"result": SCIP_RESULT.FEASIBLE}

con1 = model.createCons(myConshdlr, "my constraint", stickingatnode=True)
model.addConsNode(node, con1) 

1. Is using constraint handler the only way to create constraints locally and use addConsNode()?
   Is there any simpler way to add constraint at node, like using constraint expression in addCons()?
   Such as

         for var in self.model.vars:      
               if condition is True:
                  model.addConsNode(var == 0)

2. What does "stickingatnode" parameter in the model.createCons() do?

Thank you

[fserra]

Hi

you can read about stickingatnode here.

Regarding your other question... mmhmm. Maybe I am wrong here (@mattmilten !) but it seems to me that one can only use a constraint handler. In SCIP you can create a constraint and then add it. In PySCIPOpt, when you create an ExprCons, the only way to get a Constraint object from it is (as far as I can see) using addCons, which will create the constraint and add it.
Since, addConsNode uses a Constraint object, you can't call it with an ExprCons.

Mmm, so I think we have addCons like that, because we didn't want the users to have to create a constraint an then add it.
Maybe we can add another function to create a constraint? Or should we extend addConsNode, addConsLocal to also accept ExprCons?
Or am I missing something?

[purin0604]

Thank you for the prompt answer.
Making sure the ExprCons is only used in addCons was enough for me for now :)
I might have some more questions about the constraint handler, so I will leave this thread open for a few days.