# zlacon.f - Man Page

SRC/zlacon.f

## Synopsis

### Functions/Subroutines

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

## Function/Subroutine Documentation

### subroutine zlacon (integer n, complex*16, dimension( n ) v, complex*16, dimension( n ) x, double precision est, integer kase)

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

**Purpose:**

ZLACON estimates the 1-norm of a square, complex 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 COMPLEX*16 array, dimension (N) On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned).

*X*X is COMPLEX*16 array, dimension (N) On an intermediate return, X should be overwritten by A * X, if KASE=1, A**H * X, if KASE=2, where A**H is the conjugate transpose of A, and ZLACON must be re-called with all the other parameters unchanged.

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

*KASE*KASE is INTEGER On the initial call to ZLACON, 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**H * X. On the final return from ZLACON, KASE will again be 0.

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Further Details:**Originally named CONEST, dated March 16, 1988.

Last modified: April, 1999**Contributors:**Nick Higham, University of Manchester

**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 **113** of file **zlacon.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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