CGTSV(3)                   MathKeisan LAPACK routine                  CGTSV(3)



NAME
       CGTSV - the equation   A*X = B,

SYNOPSIS
       SUBROUTINE CGTSV( N, NRHS, DL, D, DU, B, LDB, INFO )

           INTEGER       INFO, LDB, N, NRHS

           COMPLEX       B( LDB, * ), D( * ), DL( * ), DU( * )

PURPOSE
       CGTSV  solves the equation

       where  A  is an N-by-N tridiagonal matrix, by Gaussian elimination with
       partial pivoting.

       Note that the equation  A'*X = B  may be solved  by  interchanging  the
       order of the arguments DU and DL.


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.

       DL      (input/output) COMPLEX array, dimension (N-1)
               On entry, DL must contain the (n-1) subdiagonal elements of  A.
               On  exit, DL is overwritten by the (n-2) elements of the second
               superdiagonal of the upper triangular matrix U from the LU fac-
               torization of A, in DL(1), ..., DL(n-2).

       D       (input/output) COMPLEX array, dimension (N)
               On  entry, D must contain the diagonal elements of A.  On exit,
               D is overwritten by the n diagonal elements of U.

       DU      (input/output) COMPLEX array, dimension (N-1)
               On entry, DU must contain the (n-1) superdiagonal  elements  of
               A.   On  exit,  DU  is overwritten by the (n-1) elements of the
               first superdiagonal of U.

       B       (input/output) COMPLEX 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, U(i,i) is exactly zero, and the solution has
               not been computed.  The factorization has  not  been  completed
               unless i = N.



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