SPTSV(3)       LAPACK routine of NEC Numeric Library Collection       SPTSV(3)



NAME
       SPTSV

SYNOPSIS
       SUBROUTINE SPTSV (N, NRHS, D, E, B, LDB, INFO)



PURPOSE
            SPTSV computes the solution to a real system of linear equations
            A*X = B, where A is an N-by-N symmetric positive definite tridiagonal
            matrix, and X and B are N-by-NRHS matrices.

            A is factored as A = L*D*L**T, and the factored form of A is then
            used to solve the system of equations.




ARGUMENTS
           N         (input)
                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           NRHS      (input)
                     NRHS is INTEGER
                     The number of right hand sides, i.e., the number of columns
                     of the matrix B.  NRHS >= 0.

           D         (input/output)
                     D is REAL array, dimension (N)
                     On entry, the n diagonal elements of the tridiagonal matrix
                     A.  On exit, the n diagonal elements of the diagonal matrix
                     D from the factorization A = L*D*L**T.

           E         (input/output)
                     E is REAL array, dimension (N-1)
                     On entry, the (n-1) subdiagonal elements of the tridiagonal
                     matrix A.  On exit, the (n-1) subdiagonal elements of the
                     unit bidiagonal factor L from the L*D*L**T factorization of
                     A.  (E can also be regarded as the superdiagonal of the unit
                     bidiagonal factor U from the U**T*D*U factorization of A.)

           B         (input/output)
                     B is REAL array, dimension (LDB,NRHS)
                     On entry, the N-by-NRHS right hand side matrix B.
                     On exit, if INFO = 0, the N-by-NRHS solution matrix X.

           LDB       (input)
                     LDB is INTEGER
                     The leading dimension of the array B.  LDB >= max(1,N).

           INFO      (output)
                     INFO is 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 is not
                           positive definite, and the solution has not been
                           computed.  The factorization has not been completed
                           unless i = N.



LAPACK routine                  31 October 2017                       SPTSV(3)