slaed1.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 220 行 · 第 1/2 页

</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">  Based on contributions by
</span><span class="comment">*</span><span class="comment">     Jeff Rutter, Computer Science Division, University of California
</span><span class="comment">*</span><span class="comment">     at Berkeley, USA
</span><span class="comment">*</span><span class="comment">  Modified by Francoise Tisseur, University of Tennessee.
</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">     .. Local Scalars ..
</span>      INTEGER            COLTYP, CPP1, I, IDLMDA, INDX, INDXC, INDXP,
     $                   IQ2, IS, IW, IZ, K, N1, N2
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           SCOPY, <a name="SLAED2.108"></a><a href="slaed2.f.html#SLAED2.1">SLAED2</a>, <a name="SLAED3.108"></a><a href="slaed3.f.html#SLAED3.1">SLAED3</a>, <a name="SLAMRG.108"></a><a href="slamrg.f.html#SLAMRG.1">SLAMRG</a>, <a name="XERBLA.108"></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          MAX, MIN
<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">     Test the input parameters.
</span><span class="comment">*</span><span class="comment">
</span>      INFO = 0
<span class="comment">*</span><span class="comment">
</span>      IF( N.LT.0 ) THEN
         INFO = -1
      ELSE IF( LDQ.LT.MAX( 1, N ) ) THEN
         INFO = -4
      ELSE IF( MIN( 1, N / 2 ).GT.CUTPNT .OR. ( N / 2 ).LT.CUTPNT ) THEN
         INFO = -7
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.127"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="SLAED1.127"></a><a href="slaed1.f.html#SLAED1.1">SLAED1</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">     The following values are integer pointers which indicate
</span><span class="comment">*</span><span class="comment">     the portion of the workspace
</span><span class="comment">*</span><span class="comment">     used by a particular array in <a name="SLAED2.138"></a><a href="slaed2.f.html#SLAED2.1">SLAED2</a> and <a name="SLAED3.138"></a><a href="slaed3.f.html#SLAED3.1">SLAED3</a>.
</span><span class="comment">*</span><span class="comment">
</span>      IZ = 1
      IDLMDA = IZ + N
      IW = IDLMDA + N
      IQ2 = IW + N
<span class="comment">*</span><span class="comment">
</span>      INDX = 1
      INDXC = INDX + N
      COLTYP = INDXC + N
      INDXP = COLTYP + N
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Form the z-vector which consists of the last row of Q_1 and the
</span><span class="comment">*</span><span class="comment">     first row of Q_2.
</span><span class="comment">*</span><span class="comment">
</span>      CALL SCOPY( CUTPNT, Q( CUTPNT, 1 ), LDQ, WORK( IZ ), 1 )
      CPP1 = CUTPNT + 1
      CALL SCOPY( N-CUTPNT, Q( CPP1, CPP1 ), LDQ, WORK( IZ+CUTPNT ), 1 )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Deflate eigenvalues.
</span><span class="comment">*</span><span class="comment">
</span>      CALL <a name="SLAED2.160"></a><a href="slaed2.f.html#SLAED2.1">SLAED2</a>( K, N, CUTPNT, D, Q, LDQ, INDXQ, RHO, WORK( IZ ),
     $             WORK( IDLMDA ), WORK( IW ), WORK( IQ2 ),
     $             IWORK( INDX ), IWORK( INDXC ), IWORK( INDXP ),
     $             IWORK( COLTYP ), INFO )
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 )
     $   GO TO 20
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Solve Secular Equation.
</span><span class="comment">*</span><span class="comment">
</span>      IF( K.NE.0 ) THEN
         IS = ( IWORK( COLTYP )+IWORK( COLTYP+1 ) )*CUTPNT +
     $        ( IWORK( COLTYP+1 )+IWORK( COLTYP+2 ) )*( N-CUTPNT ) + IQ2
         CALL <a name="SLAED3.173"></a><a href="slaed3.f.html#SLAED3.1">SLAED3</a>( K, N, CUTPNT, D, Q, LDQ, RHO, WORK( IDLMDA ),
     $                WORK( IQ2 ), IWORK( INDXC ), IWORK( COLTYP ),
     $                WORK( IW ), WORK( IS ), INFO )
         IF( INFO.NE.0 )
     $      GO TO 20
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Prepare the INDXQ sorting permutation.
</span><span class="comment">*</span><span class="comment">
</span>         N1 = K
         N2 = N - K
         CALL <a name="SLAMRG.183"></a><a href="slamrg.f.html#SLAMRG.1">SLAMRG</a>( N1, N2, D, 1, -1, INDXQ )
      ELSE
         DO 10 I = 1, N
            INDXQ( I ) = I
   10    CONTINUE
      END IF
<span class="comment">*</span><span class="comment">
</span>   20 CONTINUE
      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="SLAED1.193"></a><a href="slaed1.f.html#SLAED1.1">SLAED1</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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