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Diffstat (limited to 'src/fortran/lapack/zgebak.f')
| -rw-r--r-- | src/fortran/lapack/zgebak.f | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/src/fortran/lapack/zgebak.f b/src/fortran/lapack/zgebak.f new file mode 100644 index 0000000..1023601 --- /dev/null +++ b/src/fortran/lapack/zgebak.f @@ -0,0 +1,189 @@ + SUBROUTINE ZGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV, + $ INFO ) +* +* -- LAPACK routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER JOB, SIDE + INTEGER IHI, ILO, INFO, LDV, M, N +* .. +* .. Array Arguments .. + DOUBLE PRECISION SCALE( * ) + COMPLEX*16 V( LDV, * ) +* .. +* +* Purpose +* ======= +* +* ZGEBAK forms the right or left eigenvectors of a complex general +* matrix by backward transformation on the computed eigenvectors of the +* balanced matrix output by ZGEBAL. +* +* Arguments +* ========= +* +* JOB (input) CHARACTER*1 +* Specifies the type of backward transformation required: +* = 'N', do nothing, return immediately; +* = 'P', do backward transformation for permutation only; +* = 'S', do backward transformation for scaling only; +* = 'B', do backward transformations for both permutation and +* scaling. +* JOB must be the same as the argument JOB supplied to ZGEBAL. +* +* SIDE (input) CHARACTER*1 +* = 'R': V contains right eigenvectors; +* = 'L': V contains left eigenvectors. +* +* N (input) INTEGER +* The number of rows of the matrix V. N >= 0. +* +* ILO (input) INTEGER +* IHI (input) INTEGER +* The integers ILO and IHI determined by ZGEBAL. +* 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0. +* +* SCALE (input) DOUBLE PRECISION array, dimension (N) +* Details of the permutation and scaling factors, as returned +* by ZGEBAL. +* +* M (input) INTEGER +* The number of columns of the matrix V. M >= 0. +* +* V (input/output) COMPLEX*16 array, dimension (LDV,M) +* On entry, the matrix of right or left eigenvectors to be +* transformed, as returned by ZHSEIN or ZTREVC. +* On exit, V is overwritten by the transformed eigenvectors. +* +* LDV (input) INTEGER +* The leading dimension of the array V. LDV >= max(1,N). +* +* INFO (output) INTEGER +* = 0: successful exit +* < 0: if INFO = -i, the i-th argument had an illegal value. +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ONE + PARAMETER ( ONE = 1.0D+0 ) +* .. +* .. Local Scalars .. + LOGICAL LEFTV, RIGHTV + INTEGER I, II, K + DOUBLE PRECISION S +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL XERBLA, ZDSCAL, ZSWAP +* .. +* .. Intrinsic Functions .. + INTRINSIC MAX, MIN +* .. +* .. Executable Statements .. +* +* Decode and Test the input parameters +* + RIGHTV = LSAME( SIDE, 'R' ) + LEFTV = LSAME( SIDE, 'L' ) +* + INFO = 0 + IF( .NOT.LSAME( JOB, 'N' ) .AND. .NOT.LSAME( JOB, 'P' ) .AND. + $ .NOT.LSAME( JOB, 'S' ) .AND. .NOT.LSAME( JOB, 'B' ) ) THEN + INFO = -1 + ELSE IF( .NOT.RIGHTV .AND. .NOT.LEFTV ) THEN + INFO = -2 + ELSE IF( N.LT.0 ) THEN + INFO = -3 + ELSE IF( ILO.LT.1 .OR. ILO.GT.MAX( 1, N ) ) THEN + INFO = -4 + ELSE IF( IHI.LT.MIN( ILO, N ) .OR. IHI.GT.N ) THEN + INFO = -5 + ELSE IF( M.LT.0 ) THEN + INFO = -7 + ELSE IF( LDV.LT.MAX( 1, N ) ) THEN + INFO = -9 + END IF + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'ZGEBAK', -INFO ) + RETURN + END IF +* +* Quick return if possible +* + IF( N.EQ.0 ) + $ RETURN + IF( M.EQ.0 ) + $ RETURN + IF( LSAME( JOB, 'N' ) ) + $ RETURN +* + IF( ILO.EQ.IHI ) + $ GO TO 30 +* +* Backward balance +* + IF( LSAME( JOB, 'S' ) .OR. LSAME( JOB, 'B' ) ) THEN +* + IF( RIGHTV ) THEN + DO 10 I = ILO, IHI + S = SCALE( I ) + CALL ZDSCAL( M, S, V( I, 1 ), LDV ) + 10 CONTINUE + END IF +* + IF( LEFTV ) THEN + DO 20 I = ILO, IHI + S = ONE / SCALE( I ) + CALL ZDSCAL( M, S, V( I, 1 ), LDV ) + 20 CONTINUE + END IF +* + END IF +* +* Backward permutation +* +* For I = ILO-1 step -1 until 1, +* IHI+1 step 1 until N do -- +* + 30 CONTINUE + IF( LSAME( JOB, 'P' ) .OR. LSAME( JOB, 'B' ) ) THEN + IF( RIGHTV ) THEN + DO 40 II = 1, N + I = II + IF( I.GE.ILO .AND. I.LE.IHI ) + $ GO TO 40 + IF( I.LT.ILO ) + $ I = ILO - II + K = SCALE( I ) + IF( K.EQ.I ) + $ GO TO 40 + CALL ZSWAP( M, V( I, 1 ), LDV, V( K, 1 ), LDV ) + 40 CONTINUE + END IF +* + IF( LEFTV ) THEN + DO 50 II = 1, N + I = II + IF( I.GE.ILO .AND. I.LE.IHI ) + $ GO TO 50 + IF( I.LT.ILO ) + $ I = ILO - II + K = SCALE( I ) + IF( K.EQ.I ) + $ GO TO 50 + CALL ZSWAP( M, V( I, 1 ), LDV, V( K, 1 ), LDV ) + 50 CONTINUE + END IF + END IF +* + RETURN +* +* End of ZGEBAK +* + END |