If Constraint

回答済み

Rayan SAAD

2023年06月22日 20:13

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Hello,

i have a binary variables W[i,c,j,t], and i want to expres this constraint:

If for a given j and a given t W[i,c,j,t]=1  so  all other W for the same j and t most be equal to 0.

For example if W[2,0,0,2]=1  so for i in I for c in C,   W[i,c,0,2]=0.

Thank you 

関連

• Formulation
• Indicator Constraints

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  Rayan SAAD

  2023年06月22日 20:53

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  is it correct to express it like this :

  model.addConstrs( (W[i,c,k,t] ==1) >> (gp.quicksum( W[j,d,k,t] for j in range(I) for d in range(C)  if j != i if d !=c) == 0 ) for i in range(I)  for k in range(K) for t in range(T)for c in range(C))

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  Jaromił Najman

  • Gurobi Staff

  2023年06月23日 08:00 編集済み

  Hi Rayan,

  The constraint looks correct. However, you don't necessarily need an indicator constraint for that.

  If your \(\texttt{W}\) are binary then the constraints

  \[\begin{align*}
  \sum_{i \in I, c \in C} W_{i,c,k,t} = 1 \quad \forall k \in K, t \in T
  \end{align*}\]

  already make sure that exactly one \(W_{i,c,k,t}\) is \(1\) over all \(i,c\) for a fixed \(k,t\).

  Best regards, 
  Jaromił

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  Rayan SAAD

  2023年06月23日 17:04

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  Hello Jaromi,

  than you for your response,

  i wrote the constraint like this :

  for k in range(K):
      for t in range(t):
          model.addConstr(gp.quicksum(W[i,c,k,t] for i in range(I) for c in range(C))<=1)
  
  and i found W[1,1,0,2] AND W[1,0,0,2] equal to 1.
  i don't where is my error
  Thank you
  
  

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  Jaromił Najman

  • Gurobi Staff

  2023年06月23日 18:10

  I would guess that

  for t in range(t):

  is a typo and should read

  for t in range(T):

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  Rayan SAAD

  2023年06月23日 20:12

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  Thnak you !!

   

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