80 lines
2.1 KiB
Fortran
80 lines
2.1 KiB
Fortran
LOGICAL FUNCTION SB02MS( REIG, IEIG )
|
|
C
|
|
C SLICOT RELEASE 5.0.
|
|
C
|
|
C Copyright (c) 2002-2009 NICONET e.V.
|
|
C
|
|
C This program is free software: you can redistribute it and/or
|
|
C modify it under the terms of the GNU General Public License as
|
|
C published by the Free Software Foundation, either version 2 of
|
|
C the License, or (at your option) any later version.
|
|
C
|
|
C This program is distributed in the hope that it will be useful,
|
|
C but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
C MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
C GNU General Public License for more details.
|
|
C
|
|
C You should have received a copy of the GNU General Public License
|
|
C along with this program. If not, see
|
|
C <http://www.gnu.org/licenses/>.
|
|
C
|
|
C PURPOSE
|
|
C
|
|
C To select the unstable eigenvalues for solving the discrete-time
|
|
C algebraic Riccati equation.
|
|
C
|
|
C ARGUMENTS
|
|
C
|
|
C Input/Output Parameters
|
|
C
|
|
C REIG (input) DOUBLE PRECISION
|
|
C The real part of the current eigenvalue considered.
|
|
C
|
|
C IEIG (input) DOUBLE PRECISION
|
|
C The imaginary part of the current eigenvalue considered.
|
|
C
|
|
C METHOD
|
|
C
|
|
C The function value SB02MS is set to .TRUE. for an unstable
|
|
C eigenvalue (i.e., with modulus greater than or equal to one) and
|
|
C to .FALSE., otherwise.
|
|
C
|
|
C REFERENCES
|
|
C
|
|
C None.
|
|
C
|
|
C NUMERICAL ASPECTS
|
|
C
|
|
C None.
|
|
C
|
|
C CONTRIBUTOR
|
|
C
|
|
C V. Sima, Katholieke Univ. Leuven, Belgium, Aug. 1997.
|
|
C
|
|
C REVISIONS
|
|
C
|
|
C -
|
|
C
|
|
C KEYWORDS
|
|
C
|
|
C Algebraic Riccati equation, closed loop system, discrete-time
|
|
C system, optimal regulator, Schur form.
|
|
C
|
|
C ******************************************************************
|
|
C
|
|
C .. Parameters ..
|
|
DOUBLE PRECISION ONE
|
|
PARAMETER ( ONE = 1.0D0 )
|
|
C .. Scalar Arguments ..
|
|
DOUBLE PRECISION IEIG, REIG
|
|
C .. External Functions ..
|
|
DOUBLE PRECISION DLAPY2
|
|
EXTERNAL DLAPY2
|
|
C .. Executable Statements ..
|
|
C
|
|
SB02MS = DLAPY2( REIG, IEIG ).GE.ONE
|
|
C
|
|
RETURN
|
|
C *** Last line of SB02MS ***
|
|
END
|