Purpose

LA_GTSV computes the solution to a real or complex linear system of equations $AX = B$, where $A$ is a square tridiagonal matrix and $X$ and $B$ are rectangular matrices or vectors. The $LU$ decomposition is used to factor the matrix $A$ as $A = LU$, where $L$ is a product of permutation and unit lower bidiagonal matrices and $U$ is upper triangular with nonzeros in only the main diagonal and first two superdiagonals. The factored form of $A$ is then used to solve the above system.

Note: The system $A^T X = B$ may be solved by interchanging the order of the arguments ${\bf DU}$ and ${\bf DL}$.