How to Assign a Value to a Decision Variable? + How to Constrain for a Subset of Variables

Answered

Myat Thwe Naing

• March 23, 2023 08:54

enterSoC = [0.1, 0.2, 0.3]
m.addConstrs(SoC[0, b] == enterSoC[b] for b in range(noEV))
# constrain values of SoC[i+1] to SoC[i]+increment. must be done w add constraint
updatedSoC = m.addConstrs((SoC[count + 1, b] == SoC[count, b] for count in range(noPeriods) for b in range(noEV)),name="updatedSoC")

Why isn't SoC[0,0]+SoC[1,0] = 0.1 when it seems like SoC[0,1] was successfully assigned in initial value of 0.1 in the model?

 

Also, how do I rewrite a constraint so that it considers a subset of variables at each time? I want my binary decision variable schedule[i,j] to be optimised for each j by minimising the sum of their charging costs, but i get the following result. 

How should I constrain my schedule binary variable? 

0

• 

  Mario Ruthmair

  Gurobi Staff

  • March 23, 2023 14:39

  Hi,

  Why isn't SoC[0,0]+SoC[1,0] = 0.1 when it seems like SoC[0,1] was successfully assigned in initial value of 0.1 in the model?

  You set SoC[0,0] = 0.1.
  Then, you set SoC[0,0] = SoC[1,0]. This implies that also SoC[1,0] = 0.1, so the sum is of course 0.2.

  In the definition of your constraints it seems you forgot to add the "increment" in the updatedSoC constraints.

  I am not sure what exactly you want to model with your schedule-variables.
  If you want to know how to write constraints with sums of variables, then you should consider our documentation, tutorials, and examples, e.g.:

  • Python example using sums of variables
  • Gurobi Python API documentation
  • Tutorial on the Gurobi Python API, and other videos in our YouTube channel

  Best regards,
  Mario

  0

Please sign in to leave a comment.