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.

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.

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