table of contents
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zlacn2.f(3) | Library Functions Manual | /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zlacn2.f(3) |
NAME¶
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zlacn2.f
SYNOPSIS¶
Functions/Subroutines¶
subroutine ZLACN2 (n, v, x, est, kase, isave)
ZLACN2 estimates the 1-norm of a square matrix, using reverse
communication for evaluating matrix-vector products.
Function/Subroutine Documentation¶
subroutine ZLACN2 (integer n, complex*16, dimension( * ) v, complex*16, dimension( * ) x, double precision est, integer kase, integer, dimension( 3 ) isave)¶
ZLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.
Purpose:
!> !> ZLACN2 estimates the 1-norm of a square, complex 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 COMPLEX*16 array, dimension (N) !> On the final return, V = A*W, where EST = norm(V)/norm(W) !> (W is not returned). !>
X
!> X is COMPLEX*16 array, dimension (N) !> On an intermediate return, X should be overwritten by !> A * X, if KASE=1, !> A**H * X, if KASE=2, !> where A**H is the conjugate transpose of A, and ZLACN2 must be !> re-called with all the other parameters unchanged. !>
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 ZLACN2. !> On exit, EST is an estimate (a lower bound) for norm(A). !>
KASE
!> KASE is INTEGER !> On the initial call to ZLACN2, 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**H * X. !> On the final return from ZLACN2, KASE will again be 0. !>
ISAVE
!> ISAVE is INTEGER array, dimension (3) !> ISAVE is used to save variables between calls to ZLACN2 !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Further Details:
!> !> Originally named CONEST, dated March 16, 1988. !> !> Last modified: April, 1999 !> !> This is a thread safe version of ZLACON, which uses the array ISAVE !> in place of a SAVE statement, as follows: !> !> ZLACON ZLACN2 !> 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 132 of file zlacn2.f.
Author¶
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