Copyright (c) 2003, The Regents of the University of California, through Lawrence Berkeley National Laboratory (subject to receipt of any required approvals from U.S. Dept. of Energy)
All rights reserved.
The source code is distributed under BSD license, see the file License.txt at the top-level directory.
-- SuperLU routine (version 5.0) --
Univ. of California Berkeley, Xerox Palo Alto Research Center,
and Lawrence Berkeley National Lab.
July 24, 2022
int dlacon2_ |
( |
int * |
n, |
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double * |
v, |
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double * |
x, |
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int * |
isgn, |
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double * |
est, |
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int * |
kase, |
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int |
isave[3] |
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) |
| |
Purpose
=======
DLACON2 estimates the 1-norm of a square matrix A.
Reverse communication is used for evaluating matrix-vector products.
This is a thread safe version of CLACON, which uses the array ISAVE
in place of a STATIC variables, as follows:
DLACON DLACON2
jump isave[0]
j isave[1]
iter isave[2]
Arguments
=========
N (input) INT
The order of the matrix. N >= 1.
V (workspace) DOUBLE PRECISION array, dimension (N)
On the final return, V = A*W, where EST = norm(V)/norm(W)
(W is not returned).
X (input/output) DOUBLE PRECISION array, dimension (N)
On an intermediate return, X should be overwritten by
A * X, if KASE=1,
A' * X, if KASE=2,
and DLACON must be re-called with all the other parameters
unchanged.
ISGN (workspace) INT array, dimension (N)
EST (output) DOUBLE PRECISION
An estimate (a lower bound) for norm(A).
KASE (input/output) INT
On the initial call to DLACON, 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' * X.
On the final return from DLACON, KASE will again be 0.
isave (input/output) int [3]
ISAVE is INTEGER array, dimension (3)
ISAVE is used to save variables between calls to DLACON2
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.
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