zlacn2.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
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NAME

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 (integer N, complex*16, dimension( * ) V, complex*16, dimension( * ) X, double precision EST, integer KASE, 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

Univ. of Colorado Denver

NAG Ltd.

Date:

December 2016

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 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 135 of file zlacn2.f.  

Author

Generated automatically by Doxygen for LAPACK from the source code.

 

Index

NAME
SYNOPSIS
Functions/Subroutines
Function/Subroutine Documentation
subroutine zlacn2 (integer N, complex*16, dimension( * ) V, complex*16, dimension( * ) X, double precision EST, integer KASE, integer, dimension( 3 ) ISAVE)
Author