ZLACON(l) ) ZLACON(l)
ZLACON - estimate 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 (output) DOUBLE PRECISION
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 version 3.0 15 June 2000 ZLACON(l)