Contents

• NAME
• SYNOPSIS
  • F95 INTERFACE
  • C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

     cgttrs - solve one of the systems of equations  A * X  =  B,
     A**T * X = B, or A**H * X = B,

SYNOPSIS

     SUBROUTINE CGTTRS(TRANSA, N, NRHS, LOW, DIAG, UP1, UP2, IPIVOT, B,
           LDB, INFO)

     CHARACTER * 1 TRANSA
     COMPLEX LOW(*), DIAG(*), UP1(*), UP2(*), B(LDB,*)
     INTEGER N, NRHS, LDB, INFO
     INTEGER IPIVOT(*)

     SUBROUTINE CGTTRS_64(TRANSA, N, NRHS, LOW, DIAG, UP1, UP2, IPIVOT, B,
           LDB, INFO)

     CHARACTER * 1 TRANSA
     COMPLEX LOW(*), DIAG(*), UP1(*), UP2(*), B(LDB,*)
     INTEGER*8 N, NRHS, LDB, INFO
     INTEGER*8 IPIVOT(*)

  F95 INTERFACE
     SUBROUTINE GTTRS([TRANSA], [N], [NRHS], LOW, DIAG, UP1, UP2, IPIVOT,
            B, [LDB], [INFO])

     CHARACTER(LEN=1) :: TRANSA
     COMPLEX, DIMENSION(:) :: LOW, DIAG, UP1, UP2
     COMPLEX, DIMENSION(:,:) :: B
     INTEGER :: N, NRHS, LDB, INFO
     INTEGER, DIMENSION(:) :: IPIVOT

     SUBROUTINE GTTRS_64([TRANSA], [N], [NRHS], LOW, DIAG, UP1, UP2,
            IPIVOT, B, [LDB], [INFO])

     CHARACTER(LEN=1) :: TRANSA
     COMPLEX, DIMENSION(:) :: LOW, DIAG, UP1, UP2
     COMPLEX, DIMENSION(:,:) :: B
     INTEGER(8) :: N, NRHS, LDB, INFO
     INTEGER(8), DIMENSION(:) :: IPIVOT

  C INTERFACE
     #include <sunperf.h>

     void cgttrs(char transa, int n, int nrhs, complex *low, com-
               plex   *diag,  complex  *up1,  complex  *up2,  int
               *ipivot, complex *b, int ldb, int *info);
     void cgttrs_64(char transa, long n, long nrhs, complex *low,
               complex  *diag,  complex  *up1, complex *up2, long
               *ipivot, complex *b, long ldb, long *info);

PURPOSE

     cgttrs solves one of the systems of equations
        A * X = B,  A**T * X = B,  or  A**H * X = B, with a  tri-
     diagonal  matrix  A  using  the LU factorization computed by
     CGTTRF.

ARGUMENTS

     TRANSA (input)
               Specifies the form of the system of equations.   =
               'N':  A * X = B     (No transpose)
               = 'T':  A**T * X = B  (Transpose)
               = 'C':  A**H * X = B  (Conjugate transpose)

               TRANSA is defaulted to 'N' for F95 INTERFACE.

     N (input) The order of the matrix A.

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

     LOW (input)
               The (n-1) multipliers that  define  the  matrix  L
               from the LU factorization of A.

     DIAG (input)
               The n diagonal elements of  the  upper  triangular
               matrix U from the LU factorization of A.

     UP1 (input)
               The (n-1) elements of the first super-diagonal  of
               U.

     UP2 (input)
               The (n-2) elements of the second super-diagonal of
               U.

     IPIVOT (input)
               The pivot indices; for 1 <= i <= n, row i  of  the
               matrix   was   interchanged  with  row  IPIVOT(i).
               IPIVOT(i)  will  always  be  either  i   or   i+1;
               IPIVOT(i)  = i indicates a row interchange was not
               required.

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

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

     INFO (output)
               = 0:  successful exit
               < 0:  if INFO = -k, the k-th argument had an ille-
               gal value