Homepage > Man Pages > Category > Subroutines
Homepage > Man Pages > Name > L
man page of LAPACK-3
LAPACK-3: estimates the 1-norm of a square, complex matrix A
LAPACK-3 - estimates the 1-norm of a square, complex matrix A
SUBROUTINE ZLACON( N, V, X, EST, KASE )
INTEGER KASE, N
DOUBLE PRECISION EST
COMPLEX*16 V( N ), X( N )
ZLACON estimates the 1-norm of a square, complex matrix A.
Reverse communication is used for evaluating matrix-vector products.
N (input) INTEGER
The order of the matrix. N >= 1.
V (workspace) COMPLEX*16 array, dimension (N)
On the final return, V = A*W, where EST = norm(V)/norm(W)
(W is not returned).
X (input/output) COMPLEX*16 array, dimension (N)
On an intermediate return, X should be overwritten by
A * X, if KASE=1,
A' * X, if KASE=2,
where A' is the conjugate transpose of A, and ZLACON must be
re-called with all the other parameters unchanged.
EST (input/output) DOUBLE PRECISION
On entry with KASE = 1 or 2 and JUMP = 3, EST should be
unchanged from the previous call to ZLACON.
On exit, EST is an estimate (a lower bound) for norm(A).
KASE (input/output) INTEGER
On the initial call to ZLACON, KASE should be 0.
On an intermediate return, KASE will be 1 or 2, indicating
whether X should be overwritten by A * X or A' * X.
On the final return from ZLACON, KASE will again be 0.
Contributed by Nick Higham, University of Manchester.
Originally named CONEST, dated March 16, 1988.
Reference: N.J. Higham, "FORTRAN codes for estimating the one-norm of
a real or complex matrix, with applications to condition estimation",
ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988.
Last modified: April, 1999
LAPACK auxiliary routine (versionMarch 2011 LAPACK-3(3)