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 SLACN2( N, V, X, ISGN, EST, KASE, ISAVE )

           INTEGER        KASE, N

           REAL           EST

           INTEGER        ISGN( * ), ISAVE( 3 )

           REAL           V( * ), X( * )

PURPOSE

       SLACN2 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) REAL array, dimension (N)
               On the final return, V = A*W,  where  EST = norm(V)/norm(W)
               (W is not returned).

        X      (input/output) REAL array, dimension (N)
               On an intermediate return, X should be overwritten by
               A * X,   if KASE=1,
               A**T * X,  if KASE=2,
               and SLACN2 must be re-called with all the other parameters
               unchanged.

        ISGN   (workspace) INTEGER array, dimension (N)

        EST    (input/output) REAL
               On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be
               unchanged from the previous call to SLACN2.
               On exit, EST is an estimate (a lower bound) for norm(A).

        KASE   (input/output) INTEGER
               On the initial call to SLACN2, 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 SLACN2, KASE will again be 0.

        ISAVE  (input/output) INTEGER array, dimension (3)
               ISAVE is used to save variables between calls to SLACN2

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 SLACON, which uses the array ISAVE
        in place of a SAVE statement, as follows:
           SLACON     SLACN2
            JUMP     ISAVE(1)
            J        ISAVE(2)
            ITER     ISAVE(3)

 LAPACK auxiliary routine (version 3.2)     April 2011                            SLACN2(3lapack)