dlacon.f (3)  Linux Manuals
NAME
dlacon.f 
SYNOPSIS
Functions/Subroutines
subroutine dlacon (N, V, X, ISGN, EST, KASE)
DLACON estimates the 1norm of a square matrix, using reverse communication for evaluating matrixvector products.
Function/Subroutine Documentation
subroutine dlacon (integerN, double precision, dimension( * )V, double precision, dimension( * )X, integer, dimension( * )ISGN, double precisionEST, integerKASE)
DLACON estimates the 1norm of a square matrix, using reverse communication for evaluating matrixvector products.
Purpose:

DLACON estimates the 1norm of a square, real matrix A. Reverse communication is used for evaluating matrixvector products.
Parameters:

N
N is INTEGER The order of the matrix. N >= 1.
VV is DOUBLE PRECISION array, dimension (N) On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned).
XX 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 recalled with all the other parameters unchanged.
ISGNISGN is INTEGER array, dimension (N)
ESTEST 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).
KASEKASE 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 onenorm of
a real or complex matrix, with applications to condition estimation', ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381396, December 1988.
Definition at line 116 of file dlacon.f.
Author
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