CXML
        	    
LAPACK version 3.0
dtbcon(3)

PURPOSE
  DTBCON - estimate the reciprocal of the condition number of a triangular
  band matrix A, in either the 1-norm or the infinity-norm

SYNTAX
  SUBROUTINE DTBCON( NORM, UPLO, DIAG, N, KD, AB, LDAB, RCOND, WORK, IWORK,
		     INFO )

      CHARACTER	     DIAG, NORM, UPLO

      INTEGER	     INFO, KD, LDAB, N

      DOUBLE	     PRECISION RCOND

      INTEGER	     IWORK( * )

      DOUBLE	     PRECISION AB( LDAB, * ), WORK( * )

DESCRIPTION
  DTBCON estimates the reciprocal of the condition number of a triangular
  band matrix A, in either the 1-norm or the infinity-norm.  The norm of A is
  computed and an estimate is obtained for norm(inv(A)), then the reciprocal
  of the condition number is computed as
     RCOND = 1 / ( norm(A) * norm(inv(A)) ).

ARGUMENTS
  NORM	  (input) CHARACTER*1
	  Specifies whether the 1-norm condition number or the infinity-norm
	  condition number is required:
	  = '1' or 'O':	 1-norm;
	  = 'I':	 Infinity-norm.

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

  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.

  AB	  (input) DOUBLE PRECISION array, dimension (LDAB,N)
	  The upper or lower triangular band matrix A, stored in the first
	  kd+1 rows of the array. 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.

  RCOND	  (output) DOUBLE PRECISION
	  The reciprocal of the condition number of the matrix A, computed as
	  RCOND = 1/(norm(A) * norm(inv(A))).

  WORK	  (workspace) DOUBLE PRECISION array, dimension (3*N)

  IWORK	  (workspace) INTEGER array, dimension (N)

  INFO	  (output) INTEGER
	  = 0:	successful exit
	  < 0:	if INFO = -i, the i-th argument had an illegal value