zlacon()

subroutine zlacon	(	integer	n,
		complex*16, dimension( n )	v,
		complex*16, dimension( n )	x,
		double precision	est,
		integer	kase )

ZLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

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Purpose:

!>
!> ZLACON estimates the 1-norm of a square, complex matrix A.
!> Reverse communication is used for evaluating matrix-vector products.
!> 

Parameters

[in]	N	!> N is INTEGER !> The order of the matrix. N >= 1. !>
[out]	V	!> V is COMPLEX*16 array, dimension (N) !> On the final return, V = A*W, where EST = norm(V)/norm(W) !> (W is not returned). !>
[in,out]	X	!> X is COMPLEX*16 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 ZLACON must be !> re-called with all the other parameters unchanged. !>
[in,out]	EST	!> EST is 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). !>
[in,out]	KASE	!> KASE is 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**H * X. !> On the final return from ZLACON, KASE will again be 0. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

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.