confusion about adding MVar.fromlist()
AnsweredDear Gurobi-Team,
I tried to use MVar.fromlist() (https://www.gurobi.com/documentation/10.0/refman/py_mvar_fromlist.html) but the given example does not work:
import gurobipy as gp
model = gp.Model("model")
x0 = model.addVar()
x1 = model.addVar()
x2 = model.addVar()
x3 = model.addVar()
x_1d = MVar.fromlist([x0, x1, x2, x3]) # 1-D MVar
x_2d = MVar.fromlist([[x0, x1], [x2, x3]]) # 2-D MVar
I use Spyder and it already warns before runnig the script, that MVar is undefined. That's obviously true, so I added a "dummy MVar":
import gurobipy as gp
model = gp.Model("model")
x0 = model.addVar()
x1 = model.addVar()
x2 = model.addVar()
x3 = model.addVar()
MVar = model.addMVar(0)
x_1d = MVar.fromlist([x0, x1, x2, x3]) # 1-D MVar
x_2d = MVar.fromlist([[x0, x1], [x2, x3]]) # 2-D MVar
That seems to work, but is that the intended way of use?
Is it a problem, that the dummy MVar has a shape of zero and the following MVars built on it have different shapes?
Does the dummy need to remain in the model, or can I delete it after declaring the really wanted MVars?
Can I reuse the dummy as often as I want, like I did before, or do I need a dummy for each MVar in the model, as in the following?
import gurobipy as gp
model = gp.Model("model")
x0 = model.addVar()
x1 = model.addVar()
x2 = model.addVar()
x3 = model.addVar()
MVar1 = model.addMVar(0)
x_1d = MVar1.fromlist([x0, x1, x2, x3]) # 1-D MVar
MVar2 = model.addMVar(0)
x_2d = MVar2.fromlist([[x0, x1], [x2, x3]]) # 2-D MVar
Best regards
Thomas
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Gurobi Staff
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Hi Thomas,
Our example is incomplete in the sense that it doesn't show the imports. It's working on the assumption that the following import exists:
from gurobipy import *
You can make it work in your example like this:
x_1d = gp.MVar.fromlist([x0, x1, x2, x3]) # 1-D MVar x_2d = gp.MVar.fromlist([[x0, x1], [x2, x3]]) # 2-D MVar
- Riley
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Thanks, that works :-)
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