zlacn2.f (3)  Linux Manuals
NAME
zlacn2.f 
SYNOPSIS
Functions/Subroutines
subroutine zlacn2 (N, V, X, EST, KASE, ISAVE)
ZLACN2 estimates the 1norm of a square matrix, using reverse communication for evaluating matrixvector 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 1norm of a square matrix, using reverse communication for evaluating matrixvector products.
Purpose:

ZLACN2 estimates the 1norm of a square, complex matrix A. Reverse communication is used for evaluating matrixvector products.
Parameters:

N
N is INTEGER The order of the matrix. N >= 1.
VV is COMPLEX*16 array, dimension (N) On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned).
XX 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 recalled with all the other parameters unchanged.
ESTEST 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).
KASEKASE 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.
ISAVEISAVE is INTEGER array, dimension (3) ISAVE is used to save variables between calls to ZLACN2
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 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 onenorm of
a real or complex matrix, with applications to condition estimation', ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381396, December 1988.
Definition at line 134 of file zlacn2.f.
Author
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