DLACON (3) - Linux Man Pages
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 matrix-vector products.
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 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
- September 2012
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.
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