How to use non-binary variable in a conditional statement MILP?












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$begingroup$


I have a conditional statement I want to implement in a MILP.
$A$ is a non-binary variable that has known upper and lower bounds. $B$ is a known parameter. And $C$ is a binary variable.
How do I formulate the condition?



If $A < B$ then $C$ is $1$, otherwise $C$ is $0$ or $1$.



Is this possible? I am new to optimization using GAMS and i'm still figuring out how this works.










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    0












    $begingroup$


    I have a conditional statement I want to implement in a MILP.
    $A$ is a non-binary variable that has known upper and lower bounds. $B$ is a known parameter. And $C$ is a binary variable.
    How do I formulate the condition?



    If $A < B$ then $C$ is $1$, otherwise $C$ is $0$ or $1$.



    Is this possible? I am new to optimization using GAMS and i'm still figuring out how this works.










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      I have a conditional statement I want to implement in a MILP.
      $A$ is a non-binary variable that has known upper and lower bounds. $B$ is a known parameter. And $C$ is a binary variable.
      How do I formulate the condition?



      If $A < B$ then $C$ is $1$, otherwise $C$ is $0$ or $1$.



      Is this possible? I am new to optimization using GAMS and i'm still figuring out how this works.










      share|cite|improve this question











      $endgroup$




      I have a conditional statement I want to implement in a MILP.
      $A$ is a non-binary variable that has known upper and lower bounds. $B$ is a known parameter. And $C$ is a binary variable.
      How do I formulate the condition?



      If $A < B$ then $C$ is $1$, otherwise $C$ is $0$ or $1$.



      Is this possible? I am new to optimization using GAMS and i'm still figuring out how this works.







      optimization linear-programming constraints mixed-integer-programming






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      share|cite|improve this question













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      share|cite|improve this question








      edited Jan 9 at 13:19









      Klangen

      1,72811334




      1,72811334










      asked Jan 9 at 13:01









      Charles uuuCharles uuu

      32




      32






















          1 Answer
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          $begingroup$

          We know the bounds of $A$, let say $m le A le M$.



          if $m ge B$, then we clearly, we have $A ge B$.



          Hence we assume that $m < B$, then we know that



          $$frac{B-A}{B-m} le 1$$



          we consider the constraint $$frac{B-A}{B-m}le C$$



          Hence if $A < B$, then we have the left hand side of the inequality being positive and it is at most $1$, forcing $C$ to take value $1$.



          If $A ge B$, then the left hand side of the inequality is non-positive, hence not imposing constraint on $C$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks Siong !!
            $endgroup$
            – Charles uuu
            Jan 9 at 13:52











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          1 Answer
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          active

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          0












          $begingroup$

          We know the bounds of $A$, let say $m le A le M$.



          if $m ge B$, then we clearly, we have $A ge B$.



          Hence we assume that $m < B$, then we know that



          $$frac{B-A}{B-m} le 1$$



          we consider the constraint $$frac{B-A}{B-m}le C$$



          Hence if $A < B$, then we have the left hand side of the inequality being positive and it is at most $1$, forcing $C$ to take value $1$.



          If $A ge B$, then the left hand side of the inequality is non-positive, hence not imposing constraint on $C$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks Siong !!
            $endgroup$
            – Charles uuu
            Jan 9 at 13:52
















          0












          $begingroup$

          We know the bounds of $A$, let say $m le A le M$.



          if $m ge B$, then we clearly, we have $A ge B$.



          Hence we assume that $m < B$, then we know that



          $$frac{B-A}{B-m} le 1$$



          we consider the constraint $$frac{B-A}{B-m}le C$$



          Hence if $A < B$, then we have the left hand side of the inequality being positive and it is at most $1$, forcing $C$ to take value $1$.



          If $A ge B$, then the left hand side of the inequality is non-positive, hence not imposing constraint on $C$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks Siong !!
            $endgroup$
            – Charles uuu
            Jan 9 at 13:52














          0












          0








          0





          $begingroup$

          We know the bounds of $A$, let say $m le A le M$.



          if $m ge B$, then we clearly, we have $A ge B$.



          Hence we assume that $m < B$, then we know that



          $$frac{B-A}{B-m} le 1$$



          we consider the constraint $$frac{B-A}{B-m}le C$$



          Hence if $A < B$, then we have the left hand side of the inequality being positive and it is at most $1$, forcing $C$ to take value $1$.



          If $A ge B$, then the left hand side of the inequality is non-positive, hence not imposing constraint on $C$.






          share|cite|improve this answer









          $endgroup$



          We know the bounds of $A$, let say $m le A le M$.



          if $m ge B$, then we clearly, we have $A ge B$.



          Hence we assume that $m < B$, then we know that



          $$frac{B-A}{B-m} le 1$$



          we consider the constraint $$frac{B-A}{B-m}le C$$



          Hence if $A < B$, then we have the left hand side of the inequality being positive and it is at most $1$, forcing $C$ to take value $1$.



          If $A ge B$, then the left hand side of the inequality is non-positive, hence not imposing constraint on $C$.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 9 at 13:19









          Siong Thye GohSiong Thye Goh

          101k1466117




          101k1466117












          • $begingroup$
            Thanks Siong !!
            $endgroup$
            – Charles uuu
            Jan 9 at 13:52


















          • $begingroup$
            Thanks Siong !!
            $endgroup$
            – Charles uuu
            Jan 9 at 13:52
















          $begingroup$
          Thanks Siong !!
          $endgroup$
          – Charles uuu
          Jan 9 at 13:52




          $begingroup$
          Thanks Siong !!
          $endgroup$
          – Charles uuu
          Jan 9 at 13:52


















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