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

Susan Blackford 2001-08-19