1ZLACN2(1)           LAPACK auxiliary routine (version 3.1)           ZLACN2(1)
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NAME

6       ZLACN2 - the 1-norm of a square, complex matrix A
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SYNOPSIS

9       SUBROUTINE ZLACN2( N, V, X, EST, KASE, ISAVE )
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11           INTEGER        KASE, N
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13           DOUBLE         PRECISION EST
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15           INTEGER        ISAVE( 3 )
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17           COMPLEX*16     V( * ), X( * )
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PURPOSE

20       ZLACN2  estimates  the  1-norm  of a square, complex matrix A.  Reverse
21       communication is used for evaluating matrix-vector products.
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ARGUMENTS

25       N      (input) INTEGER
26              The order of the matrix.  N >= 1.
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28       V      (workspace) COMPLEX*16 array, dimension (N)
29              On the final return, V = A*W,  where  EST =  norm(V)/norm(W)  (W
30              is not returned).
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32       X      (input/output) COMPLEX*16 array, dimension (N)
33              On  an  intermediate  return,  X should be overwritten by A * X,
34              if KASE=1, A' * X,  if KASE=2, where A' is the conjugate  trans‐
35              pose  of  A,  and  ZLACN2  must  be re-called with all the other
36              parameters unchanged.
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38       EST    (input/output) DOUBLE PRECISION
39              On entry with KASE = 1 or 2 and ISAVE(1)  =  3,  EST  should  be
40              unchanged  from the previous call to ZLACN2.  On exit, EST is an
41              estimate (a lower bound) for norm(A).
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43       KASE   (input/output) INTEGER
44              On the initial call to ZLACN2, KASE should be 0.  On an interme‐
45              diate  return,  KASE will be 1 or 2, indicating whether X should
46              be overwritten by A * X  or A' * X.  On the  final  return  from
47              ZLACN2, KASE will again be 0.
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49       ISAVE  (input/output) INTEGER array, dimension (3)
50              ISAVE is used to save variables between calls to ZLACN2
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FURTHER DETAILS

53       Contributed by Nick Higham, University of Manchester.
54       Originally named CONEST, dated March 16, 1988.
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56       Reference: N.J. Higham, "FORTRAN codes for estimating the one-norm of a
57       real or complex matrix, with applications to condition estimation", ACM
58       Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988.
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60       Last modified:  April, 1999
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62       This  is a thread safe version of ZLACON, which uses the array ISAVE in
63       place of a SAVE statement, as follows:
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65          ZLACON     ZLACN2
66           JUMP     ISAVE(1)
67           J        ISAVE(2)
68           ITER     ISAVE(3)
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73 LAPACK auxiliary routine (versionNo3v.e1m)ber 2006                       ZLACN2(1)