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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine dtpt06 | ( | double precision | RCOND, |
double precision | RCONDC, | ||
character | UPLO, | ||
character | DIAG, | ||
integer | N, | ||
double precision, dimension( * ) | AP, | ||
double precision, dimension( * ) | WORK, | ||
double precision | RAT | ||
) |
DTPT06
DTPT06 computes a test ratio comparing RCOND (the reciprocal condition number of a triangular matrix A) and RCONDC, the estimate computed by DTPCON. 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.
[in] | 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)) ). |
[in] | RCONDC | RCONDC is DOUBLE PRECISION The estimate of the reciprocal condition number computed by DTPCON. |
[in] | UPLO | UPLO is CHARACTER Specifies whether the matrix A is upper or lower triangular. = 'U': Upper triangular = 'L': Lower triangular |
[in] | DIAG | DIAG is CHARACTER Specifies whether or not the matrix A is unit triangular. = 'N': Non-unit triangular = 'U': Unit triangular |
[in] | N | N is INTEGER The order of the matrix A. N >= 0. |
[in] | AP | AP is DOUBLE PRECISION array, dimension (N*(N+1)/2) The upper or lower triangular matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP((j-1)*j/2 + i) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP((j-1)*(n-j) + j*(j+1)/2 + i-j) = A(i,j) for j<=i<=n. |
[out] | WORK | WORK is DOUBLE PRECISION array, dimension (N) |
[out] | 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. |
Definition at line 113 of file dtpt06.f.