# slacon.f - Man Page

SRC/slacon.f

## Synopsis

### Functions/Subroutines

subroutine slacon (n, v, x, isgn, est, kase)
SLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

## Function/Subroutine Documentation

### subroutine slacon (integer n, real, dimension( * ) v, real, dimension( * ) x, integer, dimension( * ) isgn, real est, integer kase)

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

Purpose:

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

X

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

ISGN

ISGN is INTEGER array, dimension (N)

EST

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

KASE

KASE is INTEGER
On the initial call to SLACON, 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 SLACON, KASE will again be 0.
Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

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 114 of file slacon.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page slacon(3) is an alias of slacon.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK