STBT06 computes a test ratio comparing RCOND (the reciprocal


 condition number of a triangular matrix A) and RCONDC, the estimate


 computed by STBCON.  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 REAL


          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 REAL


          The estimate of the reciprocal condition number computed by


          STBCON.

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 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 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 REAL array, dimension (N)

RAT

          RAT is REAL


          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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