slasd1.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 257 行 · 第 1/2 页

</span><span class="comment">*</span><span class="comment">         subproblem just solved back into sorted order, i.e.
</span><span class="comment">*</span><span class="comment">         D( IDXQ( I = 1, N ) ) will be in ascending order.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  IWORK  (workspace) INTEGER array, dimension (4*N)
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  WORK   (workspace) REAL array, dimension (3*M**2+2*M)
</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 = 1, an singular value did not converge
</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">     Ming Gu and Huan Ren, Computer Science Division, University of
</span><span class="comment">*</span><span class="comment">     California at Berkeley, USA
</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><span class="comment">*</span><span class="comment">
</span>      REAL               ONE, ZERO
      PARAMETER          ( ONE = 1.0E+0, ZERO = 0.0E+0 )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      INTEGER            COLTYP, I, IDX, IDXC, IDXP, IQ, ISIGMA, IU2,
     $                   IVT2, IZ, K, LDQ, LDU2, LDVT2, M, N, N1, N2
      REAL               ORGNRM
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           <a name="SLAMRG.143"></a><a href="slamrg.f.html#SLAMRG.1">SLAMRG</a>, <a name="SLASCL.143"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>, <a name="SLASD2.143"></a><a href="slasd2.f.html#SLASD2.1">SLASD2</a>, <a name="SLASD3.143"></a><a href="slasd3.f.html#SLASD3.1">SLASD3</a>, <a name="XERBLA.143"></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">     Test the input parameters.
</span><span class="comment">*</span><span class="comment">
</span>      INFO = 0
<span class="comment">*</span><span class="comment">
</span>      IF( NL.LT.1 ) THEN
         INFO = -1
      ELSE IF( NR.LT.1 ) THEN
         INFO = -2
      ELSE IF( ( SQRE.LT.0 ) .OR. ( SQRE.GT.1 ) ) THEN
         INFO = -3
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.162"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="SLASD1.162"></a><a href="slasd1.f.html#SLASD1.1">SLASD1</a>'</span>, -INFO )
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span>      N = NL + NR + 1
      M = N + SQRE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     The following values are for bookkeeping purposes only.  They are
</span><span class="comment">*</span><span class="comment">     integer pointers which indicate the portion of the workspace
</span><span class="comment">*</span><span class="comment">     used by a particular array in <a name="SLASD2.171"></a><a href="slasd2.f.html#SLASD2.1">SLASD2</a> and <a name="SLASD3.171"></a><a href="slasd3.f.html#SLASD3.1">SLASD3</a>.
</span><span class="comment">*</span><span class="comment">
</span>      LDU2 = N
      LDVT2 = M
<span class="comment">*</span><span class="comment">
</span>      IZ = 1
      ISIGMA = IZ + M
      IU2 = ISIGMA + N
      IVT2 = IU2 + LDU2*N
      IQ = IVT2 + LDVT2*M
<span class="comment">*</span><span class="comment">
</span>      IDX = 1
      IDXC = IDX + N
      COLTYP = IDXC + N
      IDXP = COLTYP + N
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Scale.
</span><span class="comment">*</span><span class="comment">
</span>      ORGNRM = MAX( ABS( ALPHA ), ABS( BETA ) )
      D( NL+1 ) = ZERO
      DO 10 I = 1, N
         IF( ABS( D( I ) ).GT.ORGNRM ) THEN
            ORGNRM = ABS( D( I ) )
         END IF
   10 CONTINUE
      CALL <a name="SLASCL.196"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>( <span class="string">'G'</span>, 0, 0, ORGNRM, ONE, N, 1, D, N, INFO )
      ALPHA = ALPHA / ORGNRM
      BETA = BETA / ORGNRM
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Deflate singular values.
</span><span class="comment">*</span><span class="comment">
</span>      CALL <a name="SLASD2.202"></a><a href="slasd2.f.html#SLASD2.1">SLASD2</a>( NL, NR, SQRE, K, D, WORK( IZ ), ALPHA, BETA, U, LDU,
     $             VT, LDVT, WORK( ISIGMA ), WORK( IU2 ), LDU2,
     $             WORK( IVT2 ), LDVT2, IWORK( IDXP ), IWORK( IDX ),
     $             IWORK( IDXC ), IDXQ, IWORK( COLTYP ), INFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Solve Secular Equation and update singular vectors.
</span><span class="comment">*</span><span class="comment">
</span>      LDQ = K
      CALL <a name="SLASD3.210"></a><a href="slasd3.f.html#SLASD3.1">SLASD3</a>( NL, NR, SQRE, K, D, WORK( IQ ), LDQ, WORK( ISIGMA ),
     $             U, LDU, WORK( IU2 ), LDU2, VT, LDVT, WORK( IVT2 ),
     $             LDVT2, IWORK( IDXC ), IWORK( COLTYP ), WORK( IZ ),
     $             INFO )
      IF( INFO.NE.0 ) THEN
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Unscale.
</span><span class="comment">*</span><span class="comment">
</span>      CALL <a name="SLASCL.220"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>( <span class="string">'G'</span>, 0, 0, ONE, ORGNRM, N, 1, D, N, INFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Prepare the IDXQ sorting permutation.
</span><span class="comment">*</span><span class="comment">
</span>      N1 = K
      N2 = N - K
      CALL <a name="SLAMRG.226"></a><a href="slamrg.f.html#SLAMRG.1">SLAMRG</a>( N1, N2, D, 1, -1, IDXQ )
<span class="comment">*</span><span class="comment">
</span>      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="SLASD1.230"></a><a href="slasd1.f.html#SLASD1.1">SLASD1</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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