Provided by: liblapack-doc_3.3.1-1_all bug

NAME

       LAPACK-3 - estimates the 1-norm of a square, real matrix A

SYNOPSIS

       SUBROUTINE DLACN2( N, V, X, ISGN, EST, KASE, ISAVE )

           INTEGER        KASE, N

           DOUBLE         PRECISION EST

           INTEGER        ISGN( * ), ISAVE( 3 )

           DOUBLE         PRECISION V( * ), X( * )

PURPOSE

       DLACN2 estimates the 1-norm of a square, real matrix A.
        Reverse communication is used for evaluating matrix-vector products.

ARGUMENTS

        N      (input) INTEGER
               The order of the matrix.  N >= 1.

        V      (workspace) DOUBLE PRECISION array, dimension (N)
               On the final return, V = A*W,  where  EST = norm(V)/norm(W)
               (W is not returned).

        X      (input/output) 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   (workspace) INTEGER array, dimension (N)

        EST    (input/output) 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   (input/output) 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  (input/output) INTEGER array, dimension (3)
               ISAVE is used to save variables between calls to DLACN2

FURTHER DETAILS

        Contributed by Nick Higham, University of Manchester.
        Originally named SONEST, dated March 16, 1988.
        Reference: 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.
        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)

 LAPACK auxiliary routine (version 3.2)     April 2011                            DLACN2(3lapack)