TESTING/LIN/dtbt06.f(3)

NAME
TESTING/LIN/dtbt06.f

SYNOPSIS

  Functions/Subroutines
subroutine dtbt06 (rcond, rcondc, uplo, diag, n, kd, ab, ldab, work, rat)
DTBT06

Function/Subroutine Documentation

  subroutine dtbt06 (double precision rcond, double precision rcondc, character uplo, character diag, integer n, integer kd, double precision, dimension( ldab, * ) ab, integer ldab, double precision, dimension( * ) work, double precision rat)

DTBT06

Purpose:

     DTBT06 computes a test ratio comparing RCOND (the reciprocal
     condition number of a triangular matrix A) and RCONDC, the estimate
     computed by DTBCON.  Information about the triangular matrix A is
     used if one estimate is zero and the other is non-zero to decide if
     underflow in the estimate is justified.

Parameters
    RCOND

              RCOND is DOUBLE PRECISION
              The estimate of the reciprocal condition number obtained by
              forming the explicit inverse of the matrix A and computing
              RCOND = 1/( norm(A) * norm(inv(A)) ).

    RCONDC

              RCONDC is DOUBLE PRECISION
              The estimate of the reciprocal condition number computed by
              DTBCON.

    UPLO

              UPLO is CHARACTER
              Specifies whether the matrix A is upper or lower triangular.
              = 'U':  Upper triangular
              = 'L':  Lower triangular

    DIAG

              DIAG is CHARACTER
              Specifies whether or not the matrix A is unit triangular.
              = 'N':  Non-unit triangular
              = 'U':  Unit triangular

    N

              N is INTEGER
              The order of the matrix A.  N >= 0.

    KD

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

    AB

              AB is 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).

    LDAB

              LDAB is INTEGER
              The leading dimension of the array AB.  LDAB >= KD+1.

    WORK

              WORK is DOUBLE PRECISION array, dimension (N)

    RAT

              RAT is DOUBLE PRECISION
              The test ratio.  If both RCOND and RCONDC are nonzero,
                 RAT = MAX( RCOND, RCONDC )/MIN( RCOND, RCONDC ) - 1.
              If RAT = 0, the two estimates are exactly the same.

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 123 of file dtbt06.f.

Author

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