SRC/slacn2.f(3)            Library Functions Manual            SRC/slacn2.f(3)

NAME
       SRC/slacn2.f

SYNOPSIS
   Functions/Subroutines
       subroutine slacn2 (n, v, x, isgn, est, kase, isave)
           SLACN2 estimates the 1-norm of a square matrix, using reverse
           communication for evaluating matrix-vector products.

Function/Subroutine Documentation
   subroutine slacn2 (integer n, real, dimension( * ) v, real, dimension( * )
       x, integer, dimension( * ) isgn, real est, integer kase, integer,
       dimension( 3 ) isave)
       SLACN2 estimates the 1-norm of a square matrix, using reverse
       communication for evaluating matrix-vector products.

       Purpose:


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

           X

           !>          X is 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

           !>          ISGN is INTEGER array, dimension (N)
           !>

           EST

           !>          EST is 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

           !>          KASE is 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

           !>          ISAVE is INTEGER array, dimension (3)
           !>         ISAVE is used to save variables between calls to SLACN2
           !>

       Author
           Univ. of Tennessee


           Univ. of California Berkeley


           Univ. of Colorado Denver


           NAG Ltd.

       Further Details:


           !>
           !>  Originally named SONEST, dated March 16, 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)
           !>

       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 135 of file slacn2.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0                 SRC/slacn2.f(3)