Purpose

LA_PTSV computes the solution to a linear system of equations $AX = B$, where $A$ has tridiagonal form and is real symmetric or complex Hermitian and, in either case, positive definite, and where $X$ and $B$ are rectangular matrices or vectors. $A$ is factored as $A = LDL^H$, where $L$ is a unit lower bidiagonal matrix and D is a diagonal matrix. The factored form of $A$ is then used to solve the above system.