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/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/clacn2.f(3) Library Functions Manual /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/clacn2.f(3)

NAME

/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/clacn2.f

SYNOPSIS

Functions/Subroutines


subroutine CLACN2 (n, v, x, est, kase, isave)
CLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

Function/Subroutine Documentation

subroutine CLACN2 (integer n, complex, dimension( * ) v, complex, dimension( * ) x, real est, integer kase, integer, dimension( 3 ) isave)

CLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

Purpose:

!>
!> CLACN2 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 CLACN2 must be
!>         re-called with all the other parameters unchanged.
!> 

EST

!>          EST is REAL
!>         On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be
!>         unchanged from the previous call to CLACN2.
!>         On exit, EST is an estimate (a lower bound) for norm(A).
!> 

KASE

!>          KASE is INTEGER
!>         On the initial call to CLACN2, 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 CLACN2, KASE will again be 0.
!> 

ISAVE

!>          ISAVE is INTEGER array, dimension (3)
!>         ISAVE is used to save variables between calls to SLACN2
!> 

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
!>
!>  This is a thread safe version of CLACON, which uses the array ISAVE
!>  in place of a SAVE statement, as follows:
!>
!>     CLACON     CLACN2
!>      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 132 of file clacn2.f.

Author

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