Resource Allocation Problem












1












$begingroup$


Let $I, J, n in mathbb N$. Furthermore, let $mathbf M in mathbb N^{I times J}$. Finally, for $i in {1, dots, I}$ and $j in {1, dots, J}$, let $M(i,j)$ denote the element in the $i$th row and $j$th column of $mathbf M$. I'd like to solve the following optimization problem:



begin{equation}
begin{aligned}
&max_{mathbf x in mathbb N^I} && sum_{i=1}^Isum_{j = 1}^Jmin{M(i,j), x_i} \
&text{ s.t.} && sum_{i=1}^I x_i = n.
end{aligned}
end{equation}



I suspect that the problem can be solved by a "greedy" algorithm with the following form:




  1. Set $mathbf x equiv mathbf 0$.

  2. Pick any $mathbf k in arg max sum_{i=1}^Isum_{j = 1}^Jmin{M(i,j), x_i + delta_k}$. In words, find a component of $mathbf x$ which maximally increases the objective value when incremented by one -- allowing for the possibility that there may be multiple components which give maximal increase.

  3. Set $mathbf x equiv mathbf x + mathbf e_k$, where $mathbf e_k$ is the $k$th coordinate vector.

  4. If $sum_{i=1}^I x_i = n$, stop; otherwise, return to step 2.


However, I am not sure how to prove that this greedy algorithm leads to an optimal solution.



Can you help me by either providing a proof or counter-example?










share|cite|improve this question









$endgroup$

















    1












    $begingroup$


    Let $I, J, n in mathbb N$. Furthermore, let $mathbf M in mathbb N^{I times J}$. Finally, for $i in {1, dots, I}$ and $j in {1, dots, J}$, let $M(i,j)$ denote the element in the $i$th row and $j$th column of $mathbf M$. I'd like to solve the following optimization problem:



    begin{equation}
    begin{aligned}
    &max_{mathbf x in mathbb N^I} && sum_{i=1}^Isum_{j = 1}^Jmin{M(i,j), x_i} \
    &text{ s.t.} && sum_{i=1}^I x_i = n.
    end{aligned}
    end{equation}



    I suspect that the problem can be solved by a "greedy" algorithm with the following form:




    1. Set $mathbf x equiv mathbf 0$.

    2. Pick any $mathbf k in arg max sum_{i=1}^Isum_{j = 1}^Jmin{M(i,j), x_i + delta_k}$. In words, find a component of $mathbf x$ which maximally increases the objective value when incremented by one -- allowing for the possibility that there may be multiple components which give maximal increase.

    3. Set $mathbf x equiv mathbf x + mathbf e_k$, where $mathbf e_k$ is the $k$th coordinate vector.

    4. If $sum_{i=1}^I x_i = n$, stop; otherwise, return to step 2.


    However, I am not sure how to prove that this greedy algorithm leads to an optimal solution.



    Can you help me by either providing a proof or counter-example?










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      Let $I, J, n in mathbb N$. Furthermore, let $mathbf M in mathbb N^{I times J}$. Finally, for $i in {1, dots, I}$ and $j in {1, dots, J}$, let $M(i,j)$ denote the element in the $i$th row and $j$th column of $mathbf M$. I'd like to solve the following optimization problem:



      begin{equation}
      begin{aligned}
      &max_{mathbf x in mathbb N^I} && sum_{i=1}^Isum_{j = 1}^Jmin{M(i,j), x_i} \
      &text{ s.t.} && sum_{i=1}^I x_i = n.
      end{aligned}
      end{equation}



      I suspect that the problem can be solved by a "greedy" algorithm with the following form:




      1. Set $mathbf x equiv mathbf 0$.

      2. Pick any $mathbf k in arg max sum_{i=1}^Isum_{j = 1}^Jmin{M(i,j), x_i + delta_k}$. In words, find a component of $mathbf x$ which maximally increases the objective value when incremented by one -- allowing for the possibility that there may be multiple components which give maximal increase.

      3. Set $mathbf x equiv mathbf x + mathbf e_k$, where $mathbf e_k$ is the $k$th coordinate vector.

      4. If $sum_{i=1}^I x_i = n$, stop; otherwise, return to step 2.


      However, I am not sure how to prove that this greedy algorithm leads to an optimal solution.



      Can you help me by either providing a proof or counter-example?










      share|cite|improve this question









      $endgroup$




      Let $I, J, n in mathbb N$. Furthermore, let $mathbf M in mathbb N^{I times J}$. Finally, for $i in {1, dots, I}$ and $j in {1, dots, J}$, let $M(i,j)$ denote the element in the $i$th row and $j$th column of $mathbf M$. I'd like to solve the following optimization problem:



      begin{equation}
      begin{aligned}
      &max_{mathbf x in mathbb N^I} && sum_{i=1}^Isum_{j = 1}^Jmin{M(i,j), x_i} \
      &text{ s.t.} && sum_{i=1}^I x_i = n.
      end{aligned}
      end{equation}



      I suspect that the problem can be solved by a "greedy" algorithm with the following form:




      1. Set $mathbf x equiv mathbf 0$.

      2. Pick any $mathbf k in arg max sum_{i=1}^Isum_{j = 1}^Jmin{M(i,j), x_i + delta_k}$. In words, find a component of $mathbf x$ which maximally increases the objective value when incremented by one -- allowing for the possibility that there may be multiple components which give maximal increase.

      3. Set $mathbf x equiv mathbf x + mathbf e_k$, where $mathbf e_k$ is the $k$th coordinate vector.

      4. If $sum_{i=1}^I x_i = n$, stop; otherwise, return to step 2.


      However, I am not sure how to prove that this greedy algorithm leads to an optimal solution.



      Can you help me by either providing a proof or counter-example?







      optimization convex-optimization integer-programming dynamic-programming mixed-integer-programming






      share|cite|improve this question













      share|cite|improve this question











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      asked Dec 19 '18 at 7:08









      GarrettGarrett

      5761314




      5761314






















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