## Version 1.1.0

18th July 2013

Recent Changes

HSL_EA20 is a suite of Fortran 95 procedures for computing the product of the s-root of a sparse self-adjoint positive-deﬁnite matrix by a vector using a scalar product derived by a second symmetric positive-deﬁnite matrix. Given two $n×n$ symmetric positive-deﬁnite matrices $A$ and $M$, and a vector $u$, the package uses the Lanczos method, applied to the matrix pencil $\left(M,A\right)$, to approximate
${\left({M}^{-1}A\right)}^{s}u,\phantom{\rule{1em}{0ex}}s\in \left(-1,1\right).$
Reverse communication is used. Control is returned to the user for the products of $A$ with a vector $z$, of $M$ with a vector $x$, or of ${M}^{-1}$ with a vector $w$.