Estimates the Skeel condition number for a general matrix.
call sla_gercond( trans, n, a, lda, af, ldaf, ipiv, cmode, c, info, work, iwork )
call dla_gercond( trans, n, a, lda, af, ldaf, ipiv, cmode, c, info, work, iwork )
The function estimates the Skeel condition number of
op(A) * op2(C)
the cmode parameter determines
op2 as follows:
The Skeel condition number
cond(A) = norminf(|inv(A)||A|
is computed by computing scaling factors R such that
is row equilibrated and by computing the standard infinity-norm condition number.
CHARACTER*1. Must be 'N' or 'T' or 'C'.
Specifies the form of the system of equations:
trans = 'N', the system has the form A*X = B (No transpose).
trans = 'T', the system has the form AT*X = B (Transpose).
trans = 'C', the system has the form AH*X = B (Conjugate Transpose = Transpose).
INTEGER. The number of linear equations, that is, the order of the matrix A; n ≥ 0.
- a, af, c, work
REAL for sla_gercond
DOUBLE PRECISION for dla_gercond
a(lda,*) contains the original general n-by-n matrix A.
af(ldaf,*) contains factors L and U from the factorization of the general matrix A=P*L*U, as returned by ?getrf.
c, DIMENSION n. The vector
Cin the formula
op(A) * op2(C).
work is a workspace array of DIMENSION (3*n).
The second dimension of a and af must be at least
INTEGER. The leading dimension of the array a. lda ≥
INTEGER. The leading dimension of af. ldaf ≥
Array with DIMENSION n. The pivot indices from the factorization
A = P*L*Uas computed by ?getrf. Row i of the matrix was interchanged with row
op2(C)in the formula
op(A) * op2(C)as follows:
cmode = 1,
cmode = 0,
cmode = -1,
INTEGER. Workspace array with DIMENSION n.