@Article{Voemel:2009:SMA, author = "Christof Voemel", title = "ScaLAPACK's MRRR Algorithm", journal = "{ACM} Transactions on Mathematical Software", volume = "37", number = "1", accepted = "6 March 2009", upcoming = "true", abstract = " The sequential algorithm of Multiple Relatively Robust Representations, MRRR, can compute numerically orthogonal eigenvectors of a symmetric tridiagonal matrix T with O(n^2) cost. This paper describes the design of the new MRRR-based ScaLAPACK driver PDSYEVR for dense real symmetric matrices. Compared to other ScaLAPACK codes, this new code has two advantages. Unlike Divide and Conquer and QR, MRRR can compute subsets of eigenpairs at reduced cost. And in contrast to inverse iteration, it is guaranteed to produce the right answer. We describe in detail the algorithmic part of our new code and analyze its performance on a number of matrices from industrial applications.", }