zlacn2.f(3) LAPACK zlacn2.f(3)
subroutine zlacn2 (N, V, X, EST, KASE, ISAVE)
ZLACN2 estimates the 1-norm of a square matrix, using reverse communication for
evaluating matrix-vector products.
subroutine zlacn2 (integerN, complex*16, dimension( * )V, complex*16, dimension( * )X, double
precisionEST, integerKASE, integer, dimension( 3 )ISAVE)
ZLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating
ZLACN2 estimates the 1-norm of a square, complex matrix A.
Reverse communication is used for evaluating matrix-vector products.
N is INTEGER
The order of the matrix. N >= 1.
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 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 ZLACN2 must be
re-called with all the other parameters unchanged.
EST is DOUBLE PRECISION
On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be
unchanged from the previous call to ZLACN2.
On exit, EST is an estimate (a lower bound) for norm(A).
KASE is INTEGER
On the initial call to ZLACN2, 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 ZLACN2, KASE will again be 0.
ISAVE is INTEGER array, dimension (3)
ISAVE is used to save variables between calls to ZLACN2
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
Originally named CONEST, dated March 16, 1988.
Last modified: April, 1999
This is a thread safe version of ZLACON, which uses the array ISAVE
in place of a SAVE statement, as follows:
Nick Higham, University of Manchester
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 134 of file zlacn2.f.
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Version 3.4.2 Tue Sep 25 2012 zlacn2.f(3)