LAPACK  3.4.1
LAPACK: Linear Algebra PACKage
schkbk.f
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00001 *> \brief \b SCHKBK
00002 *
00003 *  =========== DOCUMENTATION ===========
00004 *
00005 * Online html documentation available at 
00006 *            http://www.netlib.org/lapack/explore-html/ 
00007 *
00008 *  Definition:
00009 *  ===========
00010 *
00011 *       SUBROUTINE SCHKBK( NIN, NOUT )
00012 * 
00013 *       .. Scalar Arguments ..
00014 *       INTEGER            NIN, NOUT
00015 *       ..
00016 *  
00017 *
00018 *> \par Purpose:
00019 *  =============
00020 *>
00021 *> \verbatim
00022 *>
00023 *> SCHKBK tests SGEBAK, a routine for backward transformation of
00024 *> the computed right or left eigenvectors if the orginal matrix
00025 *> was preprocessed by balance subroutine SGEBAL.
00026 *> \endverbatim
00027 *
00028 *  Arguments:
00029 *  ==========
00030 *
00031 *> \param[in] NIN
00032 *> \verbatim
00033 *>          NIN is INTEGER
00034 *>          The logical unit number for input.  NIN > 0.
00035 *> \endverbatim
00036 *>
00037 *> \param[in] NOUT
00038 *> \verbatim
00039 *>          NOUT is INTEGER
00040 *>          The logical unit number for output.  NOUT > 0.
00041 *> \endverbatim
00042 *
00043 *  Authors:
00044 *  ========
00045 *
00046 *> \author Univ. of Tennessee 
00047 *> \author Univ. of California Berkeley 
00048 *> \author Univ. of Colorado Denver 
00049 *> \author NAG Ltd. 
00050 *
00051 *> \date November 2011
00052 *
00053 *> \ingroup single_eig
00054 *
00055 *  =====================================================================
00056       SUBROUTINE SCHKBK( NIN, NOUT )
00057 *
00058 *  -- LAPACK test routine (version 3.4.0) --
00059 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00060 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00061 *     November 2011
00062 *
00063 *     .. Scalar Arguments ..
00064       INTEGER            NIN, NOUT
00065 *     ..
00066 *
00067 * ======================================================================
00068 *
00069 *     .. Parameters ..
00070       INTEGER            LDE
00071       PARAMETER          ( LDE = 20 )
00072       REAL               ZERO
00073       PARAMETER          ( ZERO = 0.0E0 )
00074 *     ..
00075 *     .. Local Scalars ..
00076       INTEGER            I, IHI, ILO, INFO, J, KNT, N, NINFO
00077       REAL               EPS, RMAX, SAFMIN, VMAX, X
00078 *     ..
00079 *     .. Local Arrays ..
00080       INTEGER            LMAX( 2 )
00081       REAL               E( LDE, LDE ), EIN( LDE, LDE ), SCALE( LDE )
00082 *     ..
00083 *     .. External Functions ..
00084       REAL               SLAMCH
00085       EXTERNAL           SLAMCH
00086 *     ..
00087 *     .. External Subroutines ..
00088       EXTERNAL           SGEBAK
00089 *     ..
00090 *     .. Intrinsic Functions ..
00091       INTRINSIC          ABS, MAX
00092 *     ..
00093 *     .. Executable Statements ..
00094 *
00095       LMAX( 1 ) = 0
00096       LMAX( 2 ) = 0
00097       NINFO = 0
00098       KNT = 0
00099       RMAX = ZERO
00100       EPS = SLAMCH( 'E' )
00101       SAFMIN = SLAMCH( 'S' )
00102 *
00103    10 CONTINUE
00104 *
00105       READ( NIN, FMT = * )N, ILO, IHI
00106       IF( N.EQ.0 )
00107      $   GO TO 60
00108 *
00109       READ( NIN, FMT = * )( SCALE( I ), I = 1, N )
00110       DO 20 I = 1, N
00111          READ( NIN, FMT = * )( E( I, J ), J = 1, N )
00112    20 CONTINUE
00113 *
00114       DO 30 I = 1, N
00115          READ( NIN, FMT = * )( EIN( I, J ), J = 1, N )
00116    30 CONTINUE
00117 *
00118       KNT = KNT + 1
00119       CALL SGEBAK( 'B', 'R', N, ILO, IHI, SCALE, N, E, LDE, INFO )
00120 *
00121       IF( INFO.NE.0 ) THEN
00122          NINFO = NINFO + 1
00123          LMAX( 1 ) = KNT
00124       END IF
00125 *
00126       VMAX = ZERO
00127       DO 50 I = 1, N
00128          DO 40 J = 1, N
00129             X = ABS( E( I, J )-EIN( I, J ) ) / EPS
00130             IF( ABS( E( I, J ) ).GT.SAFMIN )
00131      $         X = X / ABS( E( I, J ) )
00132             VMAX = MAX( VMAX, X )
00133    40    CONTINUE
00134    50 CONTINUE
00135 *
00136       IF( VMAX.GT.RMAX ) THEN
00137          LMAX( 2 ) = KNT
00138          RMAX = VMAX
00139       END IF
00140 *
00141       GO TO 10
00142 *
00143    60 CONTINUE
00144 *
00145       WRITE( NOUT, FMT = 9999 )
00146  9999 FORMAT( 1X, '.. test output of SGEBAK .. ' )
00147 *
00148       WRITE( NOUT, FMT = 9998 )RMAX
00149  9998 FORMAT( 1X, 'value of largest test error             = ', E12.3 )
00150       WRITE( NOUT, FMT = 9997 )LMAX( 1 )
00151  9997 FORMAT( 1X, 'example number where info is not zero   = ', I4 )
00152       WRITE( NOUT, FMT = 9996 )LMAX( 2 )
00153  9996 FORMAT( 1X, 'example number having largest error     = ', I4 )
00154       WRITE( NOUT, FMT = 9995 )NINFO
00155  9995 FORMAT( 1X, 'number of examples where info is not 0  = ', I4 )
00156       WRITE( NOUT, FMT = 9994 )KNT
00157  9994 FORMAT( 1X, 'total number of examples tested         = ', I4 )
00158 *
00159       RETURN
00160 *
00161 *     End of SCHKBK
00162 *
00163       END
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