sgtts2(3S)

NAME
     SGTTS2 - solve one of the systems of equations A*X = B or A'*X = B,

SYNOPSIS
     SUBROUTINE SGTTS2( ITRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB )

         INTEGER        ITRANS, LDB, N, NRHS

         INTEGER        IPIV( * )

         REAL           B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * )

IMPLEMENTATION
     These routines are part of the SCSL Scientific Library and can be loaded
     using either the -lscs or the -lscs_mp option.  The -lscs_mp option
     directs the linker to use the multi-processor version of the library.

     When linking to SCSL with -lscs or -lscs_mp, the default integer size is
     4 bytes (32 bits). Another version of SCSL is available in which integers
     are 8 bytes (64 bits).  This version allows the user access to larger
     memory sizes and helps when porting legacy Cray codes.  It can be loaded
     by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
     only one of the two versions; 4-byte integer and 8-byte integer library
     calls cannot be mixed.

PURPOSE
     SGTTS2 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 SGTTRF.


ARGUMENTS
     ITRANS  (input) INTEGER
             Specifies the form of the system of equations.  = 0:  A * X = B
             (No transpose)
             = 1:  A'* X = B  (Transpose)
             = 2:  A'* X = B  (Conjugate transpose = Transpose)

     N       (input) INTEGER
             The order of the matrix A.

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

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

     D       (input) REAL array, dimension (N)
             The n diagonal elements of the upper triangular matrix U from the
             LU factorization of A.
     DU      (input) REAL array, dimension (N-1)
             The (n-1) elements of the first super-diagonal of U.

     DU2     (input) REAL array, dimension (N-2)
             The (n-2) elements of the second super-diagonal 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 indicates a row interchange was not required.

     B       (input/output) REAL array, dimension (LDB,NRHS)
             On entry, the matrix of right hand side vectors B.  On exit, B is
             overwritten by the solution vectors X.

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

SEE ALSO
     INTRO_LAPACK(3S), INTRO_SCSL(3S)

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