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SUBROUTINE DCHKBK( NIN, NOUT )
*
* -- LAPACK test routine (version 3.0) --
* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
* Courant Institute, Argonne National Lab, and Rice University
* September 30, 1994
*
* .. Scalar Arguments ..
INTEGER NIN, NOUT
* ..
*
* Purpose
* =======
*
* DCHKBK tests DGEBAK, a routine for backward transformation of
* the computed right or left eigenvectors if the orginal matrix
* was preprocessed by balance subroutine DGEBAL.
*
* Arguments
* =========
*
* NIN (input) INTEGER
* The logical unit number for input. NIN > 0.
*
* NOUT (input) INTEGER
* The logical unit number for output. NOUT > 0.
*
* ======================================================================
*
* .. Parameters ..
INTEGER LDE
PARAMETER ( LDE = 20 )
DOUBLE PRECISION ZERO
PARAMETER ( ZERO = 0.0D0 )
* ..
* .. Local Scalars ..
INTEGER I, IHI, ILO, INFO, J, KNT, N, NINFO
DOUBLE PRECISION EPS, RMAX, SAFMIN, VMAX, X
* ..
* .. Local Arrays ..
INTEGER LMAX( 2 )
DOUBLE PRECISION E( LDE, LDE ), EIN( LDE, LDE ), SCALE( LDE )
* ..
* .. External Functions ..
DOUBLE PRECISION DLAMCH
EXTERNAL DLAMCH
* ..
* .. External Subroutines ..
EXTERNAL DGEBAK
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, MAX
* ..
* .. Executable Statements ..
*
LMAX( 1 ) = 0
LMAX( 2 ) = 0
NINFO = 0
KNT = 0
RMAX = ZERO
EPS = DLAMCH( 'E' )
SAFMIN = DLAMCH( 'S' )
*
10 CONTINUE
*
READ( NIN, FMT = * )N, ILO, IHI
IF( N.EQ.0 )
$ GO TO 60
*
READ( NIN, FMT = * )( SCALE( I ), I = 1, N )
DO 20 I = 1, N
READ( NIN, FMT = * )( E( I, J ), J = 1, N )
20 CONTINUE
*
DO 30 I = 1, N
READ( NIN, FMT = * )( EIN( I, J ), J = 1, N )
30 CONTINUE
*
KNT = KNT + 1
CALL DGEBAK( 'B', 'R', N, ILO, IHI, SCALE, N, E, LDE, INFO )
*
IF( INFO.NE.0 ) THEN
NINFO = NINFO + 1
LMAX( 1 ) = KNT
END IF
*
VMAX = ZERO
DO 50 I = 1, N
DO 40 J = 1, N
X = ABS( E( I, J )-EIN( I, J ) ) / EPS
IF( ABS( E( I, J ) ).GT.SAFMIN )
$ X = X / ABS( E( I, J ) )
VMAX = MAX( VMAX, X )
40 CONTINUE
50 CONTINUE
*
IF( VMAX.GT.RMAX ) THEN
LMAX( 2 ) = KNT
RMAX = VMAX
END IF
*
GO TO 10
*
60 CONTINUE
*
WRITE( NOUT, FMT = 9999 )
9999 FORMAT( 1X, '.. test output of DGEBAK .. ' )
*
WRITE( NOUT, FMT = 9998 )RMAX
9998 FORMAT( 1X, 'value of largest test error = ', D12.3 )
WRITE( NOUT, FMT = 9997 )LMAX( 1 )
9997 FORMAT( 1X, 'example number where info is not zero = ', I4 )
WRITE( NOUT, FMT = 9996 )LMAX( 2 )
9996 FORMAT( 1X, 'example number having largest error = ', I4 )
WRITE( NOUT, FMT = 9995 )NINFO
9995 FORMAT( 1X, 'number of examples where info is not 0 = ', I4 )
WRITE( NOUT, FMT = 9994 )KNT
9994 FORMAT( 1X, 'total number of examples tested = ', I4 )
*
RETURN
*
* End of DCHKBK
*
END
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