clacn2 man page on Scientific

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CLACN2(1)	    LAPACK auxiliary routine (version 3.2)	     CLACN2(1)

NAME
       CLACN2 - estimates the 1-norm of a square, complex matrix A

SYNOPSIS
       SUBROUTINE CLACN2( N, V, X, EST, KASE, ISAVE )

	   INTEGER	  KASE, N

	   REAL		  EST

	   INTEGER	  ISAVE( 3 )

	   COMPLEX	  V( * ), X( * )

PURPOSE
       CLACN2  estimates  the  1-norm  of a square, complex matrix A.  Reverse
       communication is used for evaluating matrix-vector products.

ARGUMENTS
       N      (input) INTEGER
	      The order of the matrix.	N >= 1.

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

       X      (input/output) COMPLEX array, dimension (N)
	      On  an  intermediate  return,  X should be overwritten by A * X,
	      if KASE=1, A' * X,  if KASE=2, where A' is the conjugate	trans‐
	      pose  of	A,  and	 CLACN2	 must  be re-called with all the other
	      parameters unchanged.

       EST    (input/output) 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   (input/output) INTEGER
	      On the initial call to CLACN2, KASE should be 0.	On an interme‐
	      diate  return,  KASE will be 1 or 2, indicating whether X should
	      be overwritten by A * X  or A' * X.  On the  final  return  from
	      CLACN2, KASE will again be 0.

       ISAVE  (input/output) INTEGER array, dimension (3)
	      ISAVE is used to save variables between calls to SLACN2

FURTHER DETAILS
       Contributed by Nick Higham, University of Manchester.
       Originally named CONEST, dated March 16, 1988.
       Reference: 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.  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)

 LAPACK auxiliary routine (versioNovember 2008			     CLACN2(1)
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