constraint the future state of a decision variable

Answered

carlos saenz

December 23, 2022 04:21 Edited

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Hi guys, 

Im trying to constraint state of a descicion variable but Im having problems please help and thank you!

for t in T:

  for i in R:

    if t==0:

    

      m.addConstr((v_r[(i,t)]),gb.GRB.EQUAL,(data['Reservoir'][i]['Vmin'])+(data['Demand'][t]['Wat_inflow_r0'])-(w_s[(i,t)])-(w_d[(i,t)]),name="Volume in t+1 {}{}".format(i,t))

  # restriction demand supply

    else:

      m.addConstr((v_r[(i,t)]),gb.GRB.EQUAL,(v_r[(i,t-1)])+(data['Demand'][t-1]['Wat_inflow_r0'])-(w_s[(i,t-1)])-(w_d[(i,t-1)]),name="Volume in t+1 {}{}".format(i,t))

 

when I try to do this 

else:

      m.addConstr((v_r[(i,t+1)]),gb.GRB.EQUAL,(v_r[(i,t)])+(data['Demand'][t]['Wat_inflow_r0'])-(w_s[(i,t)])-(w_d[(i,t)]),name="Volume in t+1 {}{}".format(i,t))# esto esta mal el estado t+1 del volumen debe depender del estado anterior 

  

the error is TypeError: can only concatenate str (not "int") to str

  

Related to

• Python

0

• 

  Maliheh Aramon

  • Gurobi Staff

  December 24, 2022 03:04

  Hi Carlos, 

  This is a Python error and it happens when you try to add an integer to a string.

  Since you are using the str.format() method, the error should not be related to the constraint names. 

  What are the values of the set \(\texttt{T}\)? If this set includes string values, \(\texttt{t+1}\) in \(\texttt{v_r[(i,t+1)]}\) can cause the error. 

  In case you need more help, please post a minimum working example.

  Best regards,

  Maliheh

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