Clacon.f -
subroutine clacon (N, V, X, EST, KASE)
CLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.
CLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.
Purpose:
CLACON estimates the 1-norm of a square, complex matrix A. Reverse communication is used for evaluating matrix-vector products.
Parameters:
N
N is INTEGER
The order of the matrix. N >= 1.
V
V is COMPLEX array, dimension (N)
On the final return, V = A*W, where EST = norm(V)/norm(W)
(W is not returned).
X
X is COMPLEX array, dimension (N)
On an intermediate return, X should be overwritten by
A * X, if KASE=1,
A**H * X, if KASE=2,
where A**H is the conjugate transpose of A, and CLACON must be
re-called with all the other parameters unchanged.
EST
EST is REAL
On entry with KASE = 1 or 2 and JUMP = 3, EST should be
unchanged from the previous call to CLACON.
On exit, EST is an estimate (a lower bound) for norm(A).
KASE
KASE is INTEGER
On the initial call to CLACON, 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**H * X.
On the final return from CLACON, KASE will again be 0.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Further Details:
Originally named CONEST, dated March 16, 1988.
Last modified: April, 1999
Contributors:
Nick Higham, University of Manchester
References:
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.
Definition at line 115 of file clacon.f.
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