Quadratic Optimization problem with sqrt term

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I am trying to solve a mean-variance (quadratic optimization) problem with a non-linear market impact cost term in there. This is the problem I am trying to solve



$$max alpha a - gamma x^T Sigma x - asqrt $$



where, $x_0$ is the current portfolio holding.



I am using MATLAB's quadprog program to solve this problem. How can I setup my optimization problem correctly to incorporate the sqrt term in the objective ? I am sure there is a way to do this, but I am not aware of it.







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  • 2




    Your problem is not convex due to the square root, therefore quadprog cannot optimize it. Why not use a norm?
    – LinAlg
    Jul 30 at 15:24






  • 2




    I thought market impacts were more commonly 3/2 power terms?
    – Michael Grant
    Jul 30 at 20:43







  • 2




    Regardless—quadprog will not be able to handle this. As its name implies, it supports only quadratic objectives; and if memory serves, only linear constraints. There is no way to render this objective, or even the $3/2$ version, under those limitations.
    – Michael Grant
    Jul 31 at 14:05










  • What are the decision variables? Is $a$ a decision variable? Is it only $x$?
    – Alex Shtof
    Aug 1 at 6:14














up vote
0
down vote

favorite












I am trying to solve a mean-variance (quadratic optimization) problem with a non-linear market impact cost term in there. This is the problem I am trying to solve



$$max alpha a - gamma x^T Sigma x - asqrt $$



where, $x_0$ is the current portfolio holding.



I am using MATLAB's quadprog program to solve this problem. How can I setup my optimization problem correctly to incorporate the sqrt term in the objective ? I am sure there is a way to do this, but I am not aware of it.







share|cite|improve this question

















  • 2




    Your problem is not convex due to the square root, therefore quadprog cannot optimize it. Why not use a norm?
    – LinAlg
    Jul 30 at 15:24






  • 2




    I thought market impacts were more commonly 3/2 power terms?
    – Michael Grant
    Jul 30 at 20:43







  • 2




    Regardless—quadprog will not be able to handle this. As its name implies, it supports only quadratic objectives; and if memory serves, only linear constraints. There is no way to render this objective, or even the $3/2$ version, under those limitations.
    – Michael Grant
    Jul 31 at 14:05










  • What are the decision variables? Is $a$ a decision variable? Is it only $x$?
    – Alex Shtof
    Aug 1 at 6:14












up vote
0
down vote

favorite









up vote
0
down vote

favorite











I am trying to solve a mean-variance (quadratic optimization) problem with a non-linear market impact cost term in there. This is the problem I am trying to solve



$$max alpha a - gamma x^T Sigma x - asqrt $$



where, $x_0$ is the current portfolio holding.



I am using MATLAB's quadprog program to solve this problem. How can I setup my optimization problem correctly to incorporate the sqrt term in the objective ? I am sure there is a way to do this, but I am not aware of it.







share|cite|improve this question













I am trying to solve a mean-variance (quadratic optimization) problem with a non-linear market impact cost term in there. This is the problem I am trying to solve



$$max alpha a - gamma x^T Sigma x - asqrt $$



where, $x_0$ is the current portfolio holding.



I am using MATLAB's quadprog program to solve this problem. How can I setup my optimization problem correctly to incorporate the sqrt term in the objective ? I am sure there is a way to do this, but I am not aware of it.









share|cite|improve this question












share|cite|improve this question




share|cite|improve this question








edited Jul 30 at 15:23









LinAlg

5,4111319




5,4111319









asked Jul 30 at 15:22









silencer

1134




1134







  • 2




    Your problem is not convex due to the square root, therefore quadprog cannot optimize it. Why not use a norm?
    – LinAlg
    Jul 30 at 15:24






  • 2




    I thought market impacts were more commonly 3/2 power terms?
    – Michael Grant
    Jul 30 at 20:43







  • 2




    Regardless—quadprog will not be able to handle this. As its name implies, it supports only quadratic objectives; and if memory serves, only linear constraints. There is no way to render this objective, or even the $3/2$ version, under those limitations.
    – Michael Grant
    Jul 31 at 14:05










  • What are the decision variables? Is $a$ a decision variable? Is it only $x$?
    – Alex Shtof
    Aug 1 at 6:14












  • 2




    Your problem is not convex due to the square root, therefore quadprog cannot optimize it. Why not use a norm?
    – LinAlg
    Jul 30 at 15:24






  • 2




    I thought market impacts were more commonly 3/2 power terms?
    – Michael Grant
    Jul 30 at 20:43







  • 2




    Regardless—quadprog will not be able to handle this. As its name implies, it supports only quadratic objectives; and if memory serves, only linear constraints. There is no way to render this objective, or even the $3/2$ version, under those limitations.
    – Michael Grant
    Jul 31 at 14:05










  • What are the decision variables? Is $a$ a decision variable? Is it only $x$?
    – Alex Shtof
    Aug 1 at 6:14







2




2




Your problem is not convex due to the square root, therefore quadprog cannot optimize it. Why not use a norm?
– LinAlg
Jul 30 at 15:24




Your problem is not convex due to the square root, therefore quadprog cannot optimize it. Why not use a norm?
– LinAlg
Jul 30 at 15:24




2




2




I thought market impacts were more commonly 3/2 power terms?
– Michael Grant
Jul 30 at 20:43





I thought market impacts were more commonly 3/2 power terms?
– Michael Grant
Jul 30 at 20:43





2




2




Regardless—quadprog will not be able to handle this. As its name implies, it supports only quadratic objectives; and if memory serves, only linear constraints. There is no way to render this objective, or even the $3/2$ version, under those limitations.
– Michael Grant
Jul 31 at 14:05




Regardless—quadprog will not be able to handle this. As its name implies, it supports only quadratic objectives; and if memory serves, only linear constraints. There is no way to render this objective, or even the $3/2$ version, under those limitations.
– Michael Grant
Jul 31 at 14:05












What are the decision variables? Is $a$ a decision variable? Is it only $x$?
– Alex Shtof
Aug 1 at 6:14




What are the decision variables? Is $a$ a decision variable? Is it only $x$?
– Alex Shtof
Aug 1 at 6:14















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