What is the Complexity Order of CVX for linear optimisation with determinant constraints?

Uncategorized
May 5, 2015
S

I am solving the following problem with CVX.

minimise a linear function of \mathbf{x} where \mathbf{x} is a K\times 1 column vector (all components greater than or equal to zero) and also det(\mathbf{I}+x_1\mathbf{A}_1+\cdots x_K\mathbf{A}_K)> a certain floor, where \mathbf{A}_i are M\times M are given positive definite square matrices.

Can you give some rough idea about the complexity of the problem with respect both K and M? Is it square or cube with respect to them?

M

This is outside of the scope of my personal expertise, and really outside the scope of this forum.

S

Sorry. Since it involves the inner workings of CVX, this is the place I could turn to to know how CVX solves the problem.

M

Not really the inner workings of CVX, but rather the solvers that CVX uses.

M

Perhaps Erling from MOSEK will come along. I think he has posted before on complexity of various SDPs.

E
Replying to #5

If you want a theoretical answer, then you just convert your problem to standard SDP i.e.

Next you look up the complexity of solving such an SDP. I guess that should be in the book of Boyd and Vanderberhe.
My guess is that the worst case complexity will be cubic in M. I mean checking positive definiteness will be cubic in M.

If you want to know what the practical running time is then answer would be along the line

http://docs.mosek.com/7.1/pythonapi/Usage_guidelines.html#section-node-_Usage%20guidelines_Writing%20task%20data%20to%20a%20file

adapted to the SDP case.

S
Replying to #6

Thanks a lot, but the problem is not semidefinite programming.

The constraint is on a scalar (a determinant actually), not on a matrix to be positive definite.

E
Replying to #7

Given the other answers I thought it could be rewritten as a SDP. If that is not case, then I cannot help. Sorry.

M
Replying to #8

I think Erling’s point is that the stated problem can be written as a standard SDP, even though it doesn’t take that form as you (OP) have stated it.

M

It can indeed be written as a standard SDP. Though as you have written it, it is not even convex. You need to take the $n$th root of the determinant to make it so.