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LAPACK version 3.0
dpbcon(3)

PURPOSE
  DPBCON - estimate the reciprocal of the condition number (in the 1-norm) of
  a real symmetric positive definite band matrix using the Cholesky
  factorization A = U**T*U or A = L*L**T computed by DPBTRF

SYNTAX
  SUBROUTINE DPBCON( UPLO, N, KD, AB, LDAB, ANORM, RCOND, WORK, IWORK, INFO )

      CHARACTER	     UPLO

      INTEGER	     INFO, KD, LDAB, N

      DOUBLE	     PRECISION ANORM, RCOND

      INTEGER	     IWORK( * )

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

DESCRIPTION
  DPBCON estimates the reciprocal of the condition number (in the 1-norm) of
  a real symmetric positive definite band matrix using the Cholesky
  factorization A = U**T*U or A = L*L**T computed by DPBTRF.  An estimate is
  obtained for norm(inv(A)), and the reciprocal of the condition number is
  computed as RCOND = 1 / (ANORM * norm(inv(A))).

ARGUMENTS
  UPLO	  (input) CHARACTER*1
	  = 'U':  Upper triangular factor stored in AB;
	  = 'L':  Lower triangular factor stored in AB.

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

  KD	  (input) INTEGER
	  The number of superdiagonals of the matrix A if UPLO = 'U', or the
	  number of subdiagonals if UPLO = 'L'.	 KD >= 0.

  AB	  (input) DOUBLE PRECISION array, dimension (LDAB,N)
	  The triangular factor U or L from the Cholesky factorization A =
	  U**T*U or A = L*L**T of the band matrix A, stored in the first KD+1
	  rows of the array.  The j-th column of U or L is stored in the j-th
	  column of the array AB as follows: if UPLO ='U', AB(kd+1+i-j,j) =
	  U(i,j) for max(1,j-kd)<=i<=j; if UPLO ='L', AB(1+i-j,j)    = L(i,j)
	  for j<=i<=min(n,j+kd).

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

  ANORM	  (input) DOUBLE PRECISION
	  The 1-norm (or infinity-norm) of the symmetric band matrix A.

  RCOND	  (output) DOUBLE PRECISION
	  The reciprocal of the condition number of the matrix A, computed as
	  RCOND = 1/(ANORM * AINVNM), where AINVNM is an estimate of the 1-
	  norm of inv(A) computed in this routine.

  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