Visible to Intel only — GUID: GUID-EC57BCFF-084B-4070-9C47-C733513AF6A3
Visible to Intel only — GUID: GUID-EC57BCFF-084B-4070-9C47-C733513AF6A3
?la_gercond
Estimates the Skeel condition number for a general matrix.
Syntax
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 )
Include Files
- mkl.fi
Description
The function estimates the Skeel condition number of
op(A) * op2(C)
where
the cmode parameter determines op2 as follows:
cmode Value |
op2(C) |
---|---|
1 |
C |
0 |
I |
-1 |
inv(C) |
The Skeel condition number
cond(A) = norminf(|inv(A)||A|
is computed by computing scaling factors R such that
diag(R)*A*op2(C)
is row equilibrated and by computing the standard infinity-norm condition number.
Input Parameters
- trans
-
CHARACTER*1. Must be 'N' or 'T' or 'C'.
Specifies the form of the system of equations:
If trans = 'N', the system has the form A*X = B (No transpose).
If trans = 'T', the system has the form AT*X = B (Transpose).
If trans = 'C', the system has the form AH*X = B (Conjugate Transpose = Transpose).
- n
-
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
Arrays:
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, DIMENSIONn. The vector C in 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 max(1, n).
- lda
-
INTEGER. The leading dimension of the array a. lda≥max(1,n).
- ldaf
-
INTEGER. The leading dimension of af. ldaf≥max(1, n).
- ipiv
-
INTEGER.
Array with DIMENSIONn. The pivot indices from the factorization A = P*L*U as computed by ?getrf. Row i of the matrix was interchanged with row ipiv(i).
- cmode
-
INTEGER. Determines op2(C) in the formula op(A) * op2(C) as follows:
If cmode = 1, op2(C) = C.
If cmode = 0, op2(C) = I.
If cmode = -1, op2(C) = inv(C).
- iwork
-
INTEGER. Workspace array with DIMENSIONn.
Output Parameters
- info
-
INTEGER.
If info = 0, the execution is successful.
If i > 0, the i-th parameter is invalid.