I have the below portfolio optimization problem that I need to specify in python (using cvxopt or any other optimization package). I am unable to figure out how to specify a problem containing absolute value in the objective function. The problem tries to minimize the difference between portfolio volatility and a target volatility by optimizing the constituent weights. The problem is expressed as below
Min |xTΣx – σ2target|
s.t.
1Tx = 1
x >= 0
where Σ is the covariance matrix, and σtarget is the volatility target (5%, for example)
How do I formulate the above problem in python ? I currently use cvxopt for general QP-type problems.