dlacon.f(3) LAPACK dlacon.f(3)
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.
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
DLACON estimates the 1-norm of a square, real matrix A.
Reverse communication is used for evaluating matrix-vector products.
N is INTEGER
The order of the matrix. N >= 1.
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 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
ISGN is INTEGER array, dimension (N)
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 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.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
Nick Higham, University of Manchester.
Originally named SONEST, dated March 16, 1988.
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.
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Version 3.4.2 Tue Sep 25 2012 dlacon.f(3)