dlacon.f man page

dlacon.f —

Synopsis

Functions/Subroutines

subroutine dlacon (N, V, X, ISGN, EST, KASE)
DLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

Function/Subroutine Documentation

subroutine dlacon (integerN, double precision, dimension( * )V, double precision, dimension( * )X, integer, dimension( * )ISGN, double precisionEST, integerKASE)

DLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

Purpose:

DLACON estimates the 1-norm of a square, real 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 DOUBLE PRECISION array, dimension (N)
On the final return, V = A*W,  where  EST = norm(V)/norm(W)
(W is not returned).

X

 X is DOUBLE PRECISION array, dimension (N)
On an intermediate return, X should be overwritten by
      A * X,   if KASE=1,
      A**T * X,  if KASE=2,
and DLACON must be re-called with all the other parameters
unchanged.

ISGN

ISGN is INTEGER array, dimension (N)

EST

 EST is DOUBLE PRECISION
On entry with KASE = 1 or 2 and JUMP = 3, EST should be
unchanged from the previous call to DLACON.
On exit, EST is an estimate (a lower bound) for norm(A).

KASE

 KASE is INTEGER
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**T * X.
On the final return from DLACON, KASE will again be 0.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Contributors:

Nick Higham, University of Manchester.
Originally named SONEST, dated March 16, 1988.

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 116 of file dlacon.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

dlacon(3) is an alias of dlacon.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK