clacn2.f man page

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 (integerN, complex, dimension( * )V, complex, dimension( * )X, realEST, integerKASE, 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.

Date:

September 2012

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 134 of file clacn2.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

clacn2(3) is an alias of clacn2.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK