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dlacn2.f(3) LAPACK dlacn2.f(3)NAMEdlacn2.f-SYNOPSISFunctions/Subroutines subroutine dlacn2 (N, V, X, ISGN, EST, KASE, ISAVE) DLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.Function/Subroutine Documentation subroutine dlacn2 (integerN, double precision, dimension( * )V, double precision, dimension( * )X, integer, dimension( * )ISGN, double precisionEST, integerKASE, integer, dimension( 3 )ISAVE) DLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products. Purpose: DLACN2 estimates the 1-norm of a square, real 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 DOUBLE PRECISION array, dimension (N) On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned). X 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 DLACN2 must be re-called with all the other parameters unchanged. ISGN ISGN is INTEGER array, dimension (N) EST EST is DOUBLE PRECISION On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be unchanged from the previous call to DLACN2. On exit, EST is an estimate (a lower bound) for norm(A). KASE KASE is INTEGER On the initial call to DLACN2, 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 DLACN2, KASE will again be 0. ISAVE ISAVE is INTEGER array, dimension (3) ISAVE is used to save variables between calls to DLACN2 Author: Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd. Date: September 2012 Further Details: Originally named SONEST, dated March 16, 1988. This is a thread safe version of DLACON, which uses the array ISAVE in place of a SAVE statement, as follows: DLACON DLACN2 JUMP ISAVE(1) J ISAVE(2) ITER ISAVE(3) 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 137 of file dlacn2.f.AuthorGenerated automatically by Doxygen for LAPACK from the source code.Version 3.4.2Tue Sep 25 2012 dlacn2.f(3)

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