ztbtrs(3F)

NAME
     ZTBTRS - solve a triangular system of the form   A * X = B, A**T * X = B,
     or A**H * X = B,

SYNOPSIS
     SUBROUTINE ZTBTRS( UPLO, TRANS, DIAG, N, KD, NRHS, AB, LDAB, B, LDB, INFO
                        )

         CHARACTER      DIAG, TRANS, UPLO

         INTEGER        INFO, KD, LDAB, LDB, N, NRHS

         COMPLEX*16     AB( LDAB, * ), B( LDB, * )

PURPOSE
     ZTBTRS solves a triangular system of the form

     where A is a triangular band matrix of order N, and B is an N-by-NRHS
     matrix.  A check is made to verify that A is nonsingular.


ARGUMENTS
     UPLO    (input) CHARACTER*1
             = 'U':  A is upper triangular;
             = 'L':  A is lower triangular.

     TRANS   (input) CHARACTER*1
             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)

     DIAG    (input) CHARACTER*1
             = 'N':  A is non-unit triangular;
             = 'U':  A is unit triangular.

     N       (input) INTEGER
             The order of the matrix A.  N >= 0.

     KD      (input) INTEGER
             The number of superdiagonals or subdiagonals of the triangular
             band matrix A.  KD >= 0.

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

     AB      (input) COMPLEX*16 array, dimension (LDAB,N)
             The upper or lower triangular band matrix A, stored in the first
             kd+1 rows of AB.  The j-th column of A is stored in the j-th
             column of the array AB as follows:  if UPLO = 'U', AB(kd+1+i-j,j)
             = A(i,j) for max(1,j-kd)<=i<=j; if UPLO = 'L', AB(1+i-j,j)    =
             A(i,j) for j<=i<=min(n,j+kd).  If DIAG = 'U', the diagonal
             elements of A are not referenced and are assumed to be 1.

     LDAB    (input) INTEGER
             The leading dimension of the array AB.  LDAB >= KD+1.

     B       (input/output) COMPLEX*16 array, dimension (LDB,NRHS)
             On entry, the right hand side matrix B.  On exit, if INFO = 0,
             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 illegal value
             > 0:  if INFO = i, the i-th diagonal element of A is zero,
             indicating that the matrix is singular and the solutions X have
             not been computed.