dhsein.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 436 行 · 第 1/3 页

</span><span class="comment">*</span><span class="comment">          store the eigenvectors; each selected real eigenvector
</span><span class="comment">*</span><span class="comment">          occupies one column and each selected complex eigenvector
</span><span class="comment">*</span><span class="comment">          occupies two columns.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  WORK    (workspace) DOUBLE PRECISION array, dimension ((N+2)*N)
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  IFAILL  (output) INTEGER array, dimension (MM)
</span><span class="comment">*</span><span class="comment">          If SIDE = 'L' or 'B', IFAILL(i) = j &gt; 0 if the left
</span><span class="comment">*</span><span class="comment">          eigenvector in the i-th column of VL (corresponding to the
</span><span class="comment">*</span><span class="comment">          eigenvalue w(j)) failed to converge; IFAILL(i) = 0 if the
</span><span class="comment">*</span><span class="comment">          eigenvector converged satisfactorily. If the i-th and (i+1)th
</span><span class="comment">*</span><span class="comment">          columns of VL hold a complex eigenvector, then IFAILL(i) and
</span><span class="comment">*</span><span class="comment">          IFAILL(i+1) are set to the same value.
</span><span class="comment">*</span><span class="comment">          If SIDE = 'R', IFAILL is not referenced.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  IFAILR  (output) INTEGER array, dimension (MM)
</span><span class="comment">*</span><span class="comment">          If SIDE = 'R' or 'B', IFAILR(i) = j &gt; 0 if the right
</span><span class="comment">*</span><span class="comment">          eigenvector in the i-th column of VR (corresponding to the
</span><span class="comment">*</span><span class="comment">          eigenvalue w(j)) failed to converge; IFAILR(i) = 0 if the
</span><span class="comment">*</span><span class="comment">          eigenvector converged satisfactorily. If the i-th and (i+1)th
</span><span class="comment">*</span><span class="comment">          columns of VR hold a complex eigenvector, then IFAILR(i) and
</span><span class="comment">*</span><span class="comment">          IFAILR(i+1) are set to the same value.
</span><span class="comment">*</span><span class="comment">          If SIDE = 'L', IFAILR is not referenced.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  INFO    (output) INTEGER
</span><span class="comment">*</span><span class="comment">          = 0:  successful exit
</span><span class="comment">*</span><span class="comment">          &lt; 0:  if INFO = -i, the i-th argument had an illegal value
</span><span class="comment">*</span><span class="comment">          &gt; 0:  if INFO = i, i is the number of eigenvectors which
</span><span class="comment">*</span><span class="comment">                failed to converge; see IFAILL and IFAILR for further
</span><span class="comment">*</span><span class="comment">                details.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Further Details
</span><span class="comment">*</span><span class="comment">  ===============
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Each eigenvector is normalized so that the element of largest
</span><span class="comment">*</span><span class="comment">  magnitude has magnitude 1; here the magnitude of a complex number
</span><span class="comment">*</span><span class="comment">  (x,y) is taken to be |x|+|y|.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  =====================================================================
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     .. Parameters ..
</span>      DOUBLE PRECISION   ZERO, ONE
      PARAMETER          ( ZERO = 0.0D+0, ONE = 1.0D+0 )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      LOGICAL            BOTHV, FROMQR, LEFTV, NOINIT, PAIR, RIGHTV
      INTEGER            I, IINFO, K, KL, KLN, KR, KSI, KSR, LDWORK
      DOUBLE PRECISION   BIGNUM, EPS3, HNORM, SMLNUM, ULP, UNFL, WKI,
     $                   WKR
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.179"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      DOUBLE PRECISION   <a name="DLAMCH.180"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>, <a name="DLANHS.180"></a><a href="dlanhs.f.html#DLANHS.1">DLANHS</a>
      EXTERNAL           <a name="LSAME.181"></a><a href="lsame.f.html#LSAME.1">LSAME</a>, <a name="DLAMCH.181"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>, <a name="DLANHS.181"></a><a href="dlanhs.f.html#DLANHS.1">DLANHS</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           <a name="DLAEIN.184"></a><a href="dlaein.f.html#DLAEIN.1">DLAEIN</a>, <a name="XERBLA.184"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC          ABS, MAX
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Executable Statements ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Decode and test the input parameters.
</span><span class="comment">*</span><span class="comment">
</span>      BOTHV = <a name="LSAME.193"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( SIDE, <span class="string">'B'</span> )
      RIGHTV = <a name="LSAME.194"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( SIDE, <span class="string">'R'</span> ) .OR. BOTHV
      LEFTV = <a name="LSAME.195"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( SIDE, <span class="string">'L'</span> ) .OR. BOTHV
<span class="comment">*</span><span class="comment">
</span>      FROMQR = <a name="LSAME.197"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( EIGSRC, <span class="string">'Q'</span> )
<span class="comment">*</span><span class="comment">
</span>      NOINIT = <a name="LSAME.199"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( INITV, <span class="string">'N'</span> )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Set M to the number of columns required to store the selected
</span><span class="comment">*</span><span class="comment">     eigenvectors, and standardize the array SELECT.
</span><span class="comment">*</span><span class="comment">
</span>      M = 0
      PAIR = .FALSE.
      DO 10 K = 1, N
         IF( PAIR ) THEN
            PAIR = .FALSE.
            SELECT( K ) = .FALSE.
         ELSE
            IF( WI( K ).EQ.ZERO ) THEN
               IF( SELECT( K ) )
     $            M = M + 1
            ELSE
               PAIR = .TRUE.
               IF( SELECT( K ) .OR. SELECT( K+1 ) ) THEN
                  SELECT( K ) = .TRUE.
                  M = M + 2
               END IF
            END IF
         END IF
   10 CONTINUE
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( .NOT.RIGHTV .AND. .NOT.LEFTV ) THEN
         INFO = -1
      ELSE IF( .NOT.FROMQR .AND. .NOT.<a name="LSAME.227"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( EIGSRC, <span class="string">'N'</span> ) ) THEN
         INFO = -2
      ELSE IF( .NOT.NOINIT .AND. .NOT.<a name="LSAME.229"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( INITV, <span class="string">'U'</span> ) ) THEN
         INFO = -3
      ELSE IF( N.LT.0 ) THEN
         INFO = -5
      ELSE IF( LDH.LT.MAX( 1, N ) ) THEN
         INFO = -7
      ELSE IF( LDVL.LT.1 .OR. ( LEFTV .AND. LDVL.LT.N ) ) THEN
         INFO = -11
      ELSE IF( LDVR.LT.1 .OR. ( RIGHTV .AND. LDVR.LT.N ) ) THEN
         INFO = -13
      ELSE IF( MM.LT.M ) THEN
         INFO = -14
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.243"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="DHSEIN.243"></a><a href="dhsein.f.html#DHSEIN.1">DHSEIN</a>'</span>, -INFO )
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Quick return if possible.
</span><span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.0 )
     $   RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Set machine-dependent constants.
</span><span class="comment">*</span><span class="comment">
</span>      UNFL = <a name="DLAMCH.254"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'Safe minimum'</span> )
      ULP = <a name="DLAMCH.255"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'Precision'</span> )
      SMLNUM = UNFL*( N / ULP )
      BIGNUM = ( ONE-ULP ) / SMLNUM
<span class="comment">*</span><span class="comment">
</span>      LDWORK = N + 1
<span class="comment">*</span><span class="comment">
</span>      KL = 1
      KLN = 0
      IF( FROMQR ) THEN
         KR = 0
      ELSE
         KR = N
      END IF
      KSR = 1
<span class="comment">*</span><span class="comment">
</span>      DO 120 K = 1, N
         IF( SELECT( K ) ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Compute eigenvector(s) corresponding to W(K).