zlacn2.f (3) - Linux Man Pages

zlacn2.f -

SYNOPSIS

Functions/Subroutines

subroutine zlacn2 (N, V, X, EST, KASE, ISAVE)
ZLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

Function/Subroutine Documentation

subroutine zlacn2 (integerN, complex*16, dimension( * )V, complex*16, dimension( * )X, double precisionEST, integerKASE, integer, dimension( 3 )ISAVE)

ZLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

Purpose:

ZLACN2 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*16 array, dimension (N)
On the final return, V = A*W,  where  EST = norm(V)/norm(W)
(W is not returned).

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 ZLACN2 must be
re-called with all the other parameters unchanged.

EST

EST is DOUBLE PRECISION
On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be
unchanged from the previous call to ZLACN2.
On exit, EST is an estimate (a lower bound) for norm(A).

KASE

KASE is INTEGER
On the initial call to ZLACN2, 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 ZLACN2, KASE will again be 0.

ISAVE

ISAVE is INTEGER array, dimension (3)
ISAVE is used to save variables between calls to ZLACN2

Author:

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:

September 2012

Further Details:

Originally named CONEST, dated March 16, 1988.

This is a thread safe version of ZLACON, which uses the array ISAVE
in place of a SAVE statement, as follows:

ZLACON     ZLACN2
JUMP     ISAVE(1)
J        ISAVE(2)
ITER     ISAVE(3)

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 134 of file zlacn2.f.

Author

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