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dlacon.f(3) | LAPACK | dlacon.f(3) |
NAME¶
dlacon.f -SYNOPSIS¶
Functions/Subroutines¶
subroutine dlacon (N, V, X, ISGN, EST, KASE)
Function/Subroutine Documentation¶
subroutine dlacon (integerN, double precision, dimension( * )V, double precision, dimension( * )X, integer, dimension( * )ISGN, double precisionEST, integerKASE)¶
DLACON Purpose:DLACON estimates the 1-norm of a square, real matrix A. Reverse communication is used for evaluating matrix-vector products.
N
V
X
ISGN
EST
KASE
Author:
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 unchanged.
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
NAG Ltd.
Date:
November 2011
Contributors:
Nick Higham, University of Manchester.
Originally named SONEST, dated March 16, 1988.
References:
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.
a real or complex matrix, with applications to condition estimation', ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988.
Author¶
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