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RedHat 9 (Linux i386) - man page for stbcon (redhat section l)

STBCON(l)					)					STBCON(l)

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

SYNOPSIS
       SUBROUTINE STBCON( NORM, UPLO, DIAG, N, KD, AB, LDAB, RCOND, WORK, IWORK, INFO )

	   CHARACTER	  DIAG, NORM, UPLO

	   INTEGER	  INFO, KD, LDAB, N

	   REAL 	  RCOND

	   INTEGER	  IWORK( * )

	   REAL 	  AB( LDAB, * ), WORK( * )

PURPOSE
       STBCON 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  num-
	       ber 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) REAL 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 fol-
	       lows: 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 ele-
	       ments 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) REAL
	       The reciprocal of the condition number of  the  matrix  A,  computed  as  RCOND	=
	       1/(norm(A) * norm(inv(A))).

       WORK    (workspace) REAL 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

LAPACK version 3.0			   15 June 2000 				STBCON(l)


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