DPTSV(3)                   MathKeisan LAPACK routine                  DPTSV(3)



NAME
       DPTSV  -  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

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

           INTEGER       INFO, LDB, N, NRHS

           DOUBLE        PRECISION B( LDB, * ), D( * ), E( * )

PURPOSE
       DPTSV  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) INTEGER
               The order of the matrix A.  N >= 0.

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

       D       (input/output) DOUBLE PRECISION 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) DOUBLE PRECISION 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  bidiago-
               nal factor U from the U**T*D*U factorization of A.)

       B       (input/output) DOUBLE PRECISION 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) INTEGER
               The leading dimension of the array B.  LDB >= max(1,N).

       INFO    (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 is not positive
               definite,  and the solution has not been computed.  The factor-
               ization has not been completed unless i = N.



 LAPACK routine (version 3.1)    November 2006                        DPTSV(3)