Purpose ======= LA_PTSV computes the solution to a linear system of equations A*X = 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 = L*D*L^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. ========= SUBROUTINE LA_PTSV( D, E, B, INFO=info ) REAL(), INTENT(INOUT) :: D(:) (), INTENT(INOUT) :: E(:), INTEGER, INTENT(OUT), OPTIONAL :: INFO where ::= REAL | COMPLEX ::= KIND(1.0) | KIND(1.0D0) ::= B(:,:) | B(:) Arguments ========= D (input/output) REAL array, shape (:) with size(D) = n, where n is the order of A. On entry, the diagonal of A. On exit, the diagonal of D. E (input/output) REAL or COMPLEX array, shape (:), with size(E) = n-1. On entry, the subdiagonal of A. On exit, the subdiagonal of L. B (input/output) REAL or COMPLEX array, shape (:,:) with size(B,1) = n or shape (:) with size(B) = n. On entry, the matrix B. On exit, the solution matrix X. INFO Optional (output) INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value. > 0: if INFO = i, the leading minor of order i of A is not positive definite, and the solution has not been computed. The factorization has not been completed unless i = n. If INFO is not present and an error occurs, then the program is terminated with an error message.