SUBROUTINE SCHKBK( NIN, NOUT ) * * -- LAPACK test routine (version 3.1) -- * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. * November 2006 * * .. Scalar Arguments .. INTEGER NIN, NOUT * .. * * Purpose * ======= * * SCHKBK tests SGEBAK, a routine for backward transformation of * the computed right or left eigenvectors if the orginal matrix * was preprocessed by balance subroutine SGEBAL. * * 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 ) REAL ZERO PARAMETER ( ZERO = 0.0E0 ) * .. * .. Local Scalars .. INTEGER I, IHI, ILO, INFO, J, KNT, N, NINFO REAL EPS, RMAX, SAFMIN, VMAX, X * .. * .. Local Arrays .. INTEGER LMAX( 2 ) REAL E( LDE, LDE ), EIN( LDE, LDE ), SCALE( LDE ) * .. * .. External Functions .. REAL SLAMCH EXTERNAL SLAMCH * .. * .. External Subroutines .. EXTERNAL SGEBAK * .. * .. Intrinsic Functions .. INTRINSIC ABS, MAX * .. * .. Executable Statements .. * LMAX( 1 ) = 0 LMAX( 2 ) = 0 NINFO = 0 KNT = 0 RMAX = ZERO EPS = SLAMCH( 'E' ) SAFMIN = SLAMCH( '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 SGEBAK( '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 SGEBAK .. ' ) * WRITE( NOUT, FMT = 9998 )RMAX 9998 FORMAT( 1X, 'value of largest test error = ', E12.3 ) 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 SCHKBK * END