CLACON(l) ) CLACON(l)NAME
CLACON - estimate the 1-norm of a square, complex matrix A
SYNOPSIS
SUBROUTINE CLACON( N, V, X, EST, KASE )
INTEGER KASE, N
REAL EST
COMPLEX V( N ), X( N )
PURPOSE
CLACON estimates the 1-norm of a square, complex matrix A. Reverse com‐
munication is used for evaluating matrix-vector products.
ARGUMENTS
N (input) INTEGER
The order of the matrix. N >= 1.
V (workspace) COMPLEX array, dimension (N)
On the final return, V = A*W, where EST = norm(V)/norm(W) (W
is not returned).
X (input/output) COMPLEX 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 trans‐
pose of A, and CLACON must be re-called with all the other
parameters unchanged.
EST (output) REAL
An estimate (a lower bound) for norm(A).
KASE (input/output) INTEGER
On the initial call to CLACON, KASE should be 0. On an interme‐
diate return, KASE will be 1 or 2, indicating whether X should
be overwritten by A * X or A' * X. On the final return from
CLACON, KASE will again be 0.
FURTHER DETAILS
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 version 3.0 15 June 2000 CLACON(l)
