# Problem 34: Linear Algebra Computation

Consider also the following problem. Let $A$ be an $m\times n$ matrix and let $k$ be a rank parameter. Let $P_{A,k}$ be the projection matrix on the best rank-$k$ left (or right) singular subspace. The goal is to compute the diagonal of $P_{A,k}$ exactly or approximately in a small number of passes in the streaming model, or even better, in a new model that addresses the aforementioned shortcoming.