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NAME
     dgttrs - solve one of the systems of equations  A*X =  B  or
     A'*X = B,

SYNOPSIS
     SUBROUTINE DGTTRS( TRANS, N, NRHS, DL, D, DU, DU2, IPIV,  B,
               LDB, INFO )

     CHARACTER TRANS

     INTEGER INFO, LDB, N, NRHS

     INTEGER IPIV( * )

     DOUBLE PRECISION B( LDB, * ), D( * ), DL( * ), DU( * ), DU2(
               * )



     #include <sunperf.h>

     void dgttrs(char trans, int n, int nrhs, double *dl,  double
               *d,  double  *du, double *du2, int *ipivot, double
               *db, int ldb, int *info) ;

PURPOSE
     DGTTRS solves one of the systems of equations
        A*X = B  or  A'*X = B, with a tridiagonal matrix A  using
     the LU factorization computed by DGTTRF.


ARGUMENTS
     TRANS     (input) CHARACTER
               Specifies the form of the system of equations:
               = 'N':  A * X = B  (No transpose)
               = 'T':  A'* X = B  (Transpose)
               = 'C':  A'* X = B  (Conjugate  transpose  =  Tran-
               spose)

     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) DOUBLE PRECISION array, dimension (N-1)
               The (n-1) multipliers that  define  the  matrix  L
               from the LU factorization of A.

     D         (input) DOUBLE PRECISION array, dimension (N)
               The n diagonal elements of  the  upper  triangular
               matrix U from the LU factorization of A.

     DU        (input) DOUBLE PRECISION array, dimension (N-1)
               The (n-1) elements of the first  superdiagonal  of
               U.

     DU2       (input) DOUBLE PRECISION array, dimension (N-2)
               The (n-2) elements of the second superdiagonal  of
               U.

     IPIV      (input) INTEGER array, dimension (N)
               The pivot indices; for 1 <= i <= n, row i  of  the
               matrix was interchanged with row IPIV(i).  IPIV(i)
               will always be either i or i+1; IPIV(i) = i  indi-
               cates a row interchange was not required.

     B         (input/output) DOUBLE PRECISION  array,  dimension
               (LDB,NRHS)
               On entry, the right hand side matrix B.  On  exit,
               B is overwritten by the 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 ille-
               gal value

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