Annotation of rpl/lapack/lapack/zgebak.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE ZGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV,
! 2: $ INFO )
! 3: *
! 4: * -- LAPACK routine (version 3.2) --
! 5: * -- LAPACK is a software package provided by Univ. of Tennessee, --
! 6: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 7: * November 2006
! 8: *
! 9: * .. Scalar Arguments ..
! 10: CHARACTER JOB, SIDE
! 11: INTEGER IHI, ILO, INFO, LDV, M, N
! 12: * ..
! 13: * .. Array Arguments ..
! 14: DOUBLE PRECISION SCALE( * )
! 15: COMPLEX*16 V( LDV, * )
! 16: * ..
! 17: *
! 18: * Purpose
! 19: * =======
! 20: *
! 21: * ZGEBAK forms the right or left eigenvectors of a complex general
! 22: * matrix by backward transformation on the computed eigenvectors of the
! 23: * balanced matrix output by ZGEBAL.
! 24: *
! 25: * Arguments
! 26: * =========
! 27: *
! 28: * JOB (input) CHARACTER*1
! 29: * Specifies the type of backward transformation required:
! 30: * = 'N', do nothing, return immediately;
! 31: * = 'P', do backward transformation for permutation only;
! 32: * = 'S', do backward transformation for scaling only;
! 33: * = 'B', do backward transformations for both permutation and
! 34: * scaling.
! 35: * JOB must be the same as the argument JOB supplied to ZGEBAL.
! 36: *
! 37: * SIDE (input) CHARACTER*1
! 38: * = 'R': V contains right eigenvectors;
! 39: * = 'L': V contains left eigenvectors.
! 40: *
! 41: * N (input) INTEGER
! 42: * The number of rows of the matrix V. N >= 0.
! 43: *
! 44: * ILO (input) INTEGER
! 45: * IHI (input) INTEGER
! 46: * The integers ILO and IHI determined by ZGEBAL.
! 47: * 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
! 48: *
! 49: * SCALE (input) DOUBLE PRECISION array, dimension (N)
! 50: * Details of the permutation and scaling factors, as returned
! 51: * by ZGEBAL.
! 52: *
! 53: * M (input) INTEGER
! 54: * The number of columns of the matrix V. M >= 0.
! 55: *
! 56: * V (input/output) COMPLEX*16 array, dimension (LDV,M)
! 57: * On entry, the matrix of right or left eigenvectors to be
! 58: * transformed, as returned by ZHSEIN or ZTREVC.
! 59: * On exit, V is overwritten by the transformed eigenvectors.
! 60: *
! 61: * LDV (input) INTEGER
! 62: * The leading dimension of the array V. LDV >= max(1,N).
! 63: *
! 64: * INFO (output) INTEGER
! 65: * = 0: successful exit
! 66: * < 0: if INFO = -i, the i-th argument had an illegal value.
! 67: *
! 68: * =====================================================================
! 69: *
! 70: * .. Parameters ..
! 71: DOUBLE PRECISION ONE
! 72: PARAMETER ( ONE = 1.0D+0 )
! 73: * ..
! 74: * .. Local Scalars ..
! 75: LOGICAL LEFTV, RIGHTV
! 76: INTEGER I, II, K
! 77: DOUBLE PRECISION S
! 78: * ..
! 79: * .. External Functions ..
! 80: LOGICAL LSAME
! 81: EXTERNAL LSAME
! 82: * ..
! 83: * .. External Subroutines ..
! 84: EXTERNAL XERBLA, ZDSCAL, ZSWAP
! 85: * ..
! 86: * .. Intrinsic Functions ..
! 87: INTRINSIC MAX, MIN
! 88: * ..
! 89: * .. Executable Statements ..
! 90: *
! 91: * Decode and Test the input parameters
! 92: *
! 93: RIGHTV = LSAME( SIDE, 'R' )
! 94: LEFTV = LSAME( SIDE, 'L' )
! 95: *
! 96: INFO = 0
! 97: IF( .NOT.LSAME( JOB, 'N' ) .AND. .NOT.LSAME( JOB, 'P' ) .AND.
! 98: $ .NOT.LSAME( JOB, 'S' ) .AND. .NOT.LSAME( JOB, 'B' ) ) THEN
! 99: INFO = -1
! 100: ELSE IF( .NOT.RIGHTV .AND. .NOT.LEFTV ) THEN
! 101: INFO = -2
! 102: ELSE IF( N.LT.0 ) THEN
! 103: INFO = -3
! 104: ELSE IF( ILO.LT.1 .OR. ILO.GT.MAX( 1, N ) ) THEN
! 105: INFO = -4
! 106: ELSE IF( IHI.LT.MIN( ILO, N ) .OR. IHI.GT.N ) THEN
! 107: INFO = -5
! 108: ELSE IF( M.LT.0 ) THEN
! 109: INFO = -7
! 110: ELSE IF( LDV.LT.MAX( 1, N ) ) THEN
! 111: INFO = -9
! 112: END IF
! 113: IF( INFO.NE.0 ) THEN
! 114: CALL XERBLA( 'ZGEBAK', -INFO )
! 115: RETURN
! 116: END IF
! 117: *
! 118: * Quick return if possible
! 119: *
! 120: IF( N.EQ.0 )
! 121: $ RETURN
! 122: IF( M.EQ.0 )
! 123: $ RETURN
! 124: IF( LSAME( JOB, 'N' ) )
! 125: $ RETURN
! 126: *
! 127: IF( ILO.EQ.IHI )
! 128: $ GO TO 30
! 129: *
! 130: * Backward balance
! 131: *
! 132: IF( LSAME( JOB, 'S' ) .OR. LSAME( JOB, 'B' ) ) THEN
! 133: *
! 134: IF( RIGHTV ) THEN
! 135: DO 10 I = ILO, IHI
! 136: S = SCALE( I )
! 137: CALL ZDSCAL( M, S, V( I, 1 ), LDV )
! 138: 10 CONTINUE
! 139: END IF
! 140: *
! 141: IF( LEFTV ) THEN
! 142: DO 20 I = ILO, IHI
! 143: S = ONE / SCALE( I )
! 144: CALL ZDSCAL( M, S, V( I, 1 ), LDV )
! 145: 20 CONTINUE
! 146: END IF
! 147: *
! 148: END IF
! 149: *
! 150: * Backward permutation
! 151: *
! 152: * For I = ILO-1 step -1 until 1,
! 153: * IHI+1 step 1 until N do --
! 154: *
! 155: 30 CONTINUE
! 156: IF( LSAME( JOB, 'P' ) .OR. LSAME( JOB, 'B' ) ) THEN
! 157: IF( RIGHTV ) THEN
! 158: DO 40 II = 1, N
! 159: I = II
! 160: IF( I.GE.ILO .AND. I.LE.IHI )
! 161: $ GO TO 40
! 162: IF( I.LT.ILO )
! 163: $ I = ILO - II
! 164: K = SCALE( I )
! 165: IF( K.EQ.I )
! 166: $ GO TO 40
! 167: CALL ZSWAP( M, V( I, 1 ), LDV, V( K, 1 ), LDV )
! 168: 40 CONTINUE
! 169: END IF
! 170: *
! 171: IF( LEFTV ) THEN
! 172: DO 50 II = 1, N
! 173: I = II
! 174: IF( I.GE.ILO .AND. I.LE.IHI )
! 175: $ GO TO 50
! 176: IF( I.LT.ILO )
! 177: $ I = ILO - II
! 178: K = SCALE( I )
! 179: IF( K.EQ.I )
! 180: $ GO TO 50
! 181: CALL ZSWAP( M, V( I, 1 ), LDV, V( K, 1 ), LDV )
! 182: 50 CONTINUE
! 183: END IF
! 184: END IF
! 185: *
! 186: RETURN
! 187: *
! 188: * End of ZGEBAK
! 189: *
! 190: END
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