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NAME
     zlacon - estimate the 1-norm of a square, complex matrix A

SYNOPSIS
     SUBROUTINE ZLACON( N, V, X, EST, KASE )

     INTEGER KASE, N

     DOUBLE PRECISION EST

     COMPLEX*16 V( N ), X( N )



     #include <sunperf.h>

     void zlacon(int n, doublecomplex *v, doublecomplex *zx, dou-
               ble *est, int *kase) ;

PURPOSE
     ZLACON estimates the 1-norm of a square, complex  matrix  A.
     Reverse  communication  is used for evaluating matrix-vector
     products.  If the initial call is made with  KASE  equal  to
     -255  and  subsequent  intermediate  calls made as described
     below then this subroutine is MT-safe, otherwise it  is  not
     MT-safe.


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

     V         (workspace) COMPLEX*16 array, dimension (N)
               On the final  return,  V  =  A*W,   where   EST  =
               norm(V)/norm(W) (W is not returned).

     X         (input/output) COMPLEX*16 array, dimension (N)
               On an MT-unsafe intermediate return, X  should  be
               overwritten  by A * X if KASE=1, A' * X if KASE=2,
               where A' is the conjugate transpose of A, and ZLA-
               CON  must  be re-called with all the other parame-
               ters  unchanged.   On  an   MT-safe   intermediate
               return,  X  should be overwritten by A * X if bits
               8-11  of  KASE=0001,  A'  *  X  if  bits  8-11  of
               KASE=0010,  where A' is the conjugate transpose of
               A, and ZLACON must be re-called with all the other
               parameters   unchanged.    The   MT-safe  mode  is
               described below in the  description  of  the  KASE
               argument.

     EST       (output) DOUBLE PRECISION
               An estimate (a lower bound) for norm(A).

     KASE      (input/output) INTEGER
               On the initial call to ZLACON, KASE should be 0 or
               -255.   If  KASE  was supplied as 0 on the initial
               call then on an intermediate return, KASE will  be
               1 or 2, indicating whether X should be overwritten
               by A * X  or A' * X.  If KASE was supplied as -255
               on  the  initial  call  then  on  an  intermediate
               return, the low 8 bits of KASE will be 0  and  the
               next  4  bits  will  contain  1  or  2, indicating
               whether X should be overwritten by A * X  or A'  *
               X.   On  the  final  return from ZLACON, KASE will
               again be 0.  If the initial call is made with KASE
               equal  to -255 then this subroutine is MT-safe but
               does not conform to the  standard  LAPACK  calling
               sequence.   If  the initial call is made with KASE
               equal to 0 then it is not MT-safe, but it conforms
               to the standard LAPACK calling sequence.

FURTHER DETAILS
     Contributed by Nick Higham, University of Manchester.
     Originally named CONEST, dated 27 Jun 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.

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