## An Efficient Algorithm for Minimizing a Sum of P-Norms

### Guoliang Xue and Yinyu Ye

We study the problem of minimizing a sum of $p$-norms where $p$ is a fixed real number in the interval $[1, \infty]$. Several practical algorithms have been proposed to solve this problem. However, none of them has a known polynomial time complexity. In this paper, we transform the problem into standard conic form. Unlike those in most convex optimization problems, the cone for the $p$-norm problem is {\em not} self-dual unless $p=2$. Nevertheless, we are able to construct two logarithmically homogeneous self-concordant barrier functions for this problem. The barrier parameter of the first barrier function does not depend on $p$. The barrier parameter of the second barrier function increases with $p$. Using both barrier functions, we present a primal-dual potential reduction algorithm to compute an $\epsilon$-optimal solution in polynomial time that is independent of $p$. Computational experiences of a Matlab implementation are also reported.

Working Paper, Department of Computer Science, The University of Vermont, Burlington, VT 05405-0156.

Contact: yinyu-ye@uiowa.edu