dlasd0.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 255 行 · 第 1/2 页

         INFO = -6
      ELSE IF( LDVT.LT.M ) THEN
         INFO = -8
      ELSE IF( SMLSIZ.LT.3 ) THEN
         INFO = -9
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.117"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="DLASD0.117"></a><a href="dlasd0.f.html#DLASD0.1">DLASD0</a>'</span>, -INFO )
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     If the input matrix is too small, call <a name="DLASDQ.121"></a><a href="dlasdq.f.html#DLASDQ.1">DLASDQ</a> to find the SVD.
</span><span class="comment">*</span><span class="comment">
</span>      IF( N.LE.SMLSIZ ) THEN
         CALL <a name="DLASDQ.124"></a><a href="dlasdq.f.html#DLASDQ.1">DLASDQ</a>( <span class="string">'U'</span>, SQRE, N, M, N, 0, D, E, VT, LDVT, U, LDU, U,
     $                LDU, WORK, INFO )
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Set up the computation tree.
</span><span class="comment">*</span><span class="comment">
</span>      INODE = 1
      NDIML = INODE + N
      NDIMR = NDIML + N
      IDXQ = NDIMR + N
      IWK = IDXQ + N
      CALL <a name="DLASDT.136"></a><a href="dlasdt.f.html#DLASDT.1">DLASDT</a>( N, NLVL, ND, IWORK( INODE ), IWORK( NDIML ),
     $             IWORK( NDIMR ), SMLSIZ )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     For the nodes on bottom level of the tree, solve
</span><span class="comment">*</span><span class="comment">     their subproblems by <a name="DLASDQ.140"></a><a href="dlasdq.f.html#DLASDQ.1">DLASDQ</a>.
</span><span class="comment">*</span><span class="comment">
</span>      NDB1 = ( ND+1 ) / 2
      NCC = 0
      DO 30 I = NDB1, ND
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     IC : center row of each node
</span><span class="comment">*</span><span class="comment">     NL : number of rows of left  subproblem
</span><span class="comment">*</span><span class="comment">     NR : number of rows of right subproblem
</span><span class="comment">*</span><span class="comment">     NLF: starting row of the left   subproblem
</span><span class="comment">*</span><span class="comment">     NRF: starting row of the right  subproblem
</span><span class="comment">*</span><span class="comment">
</span>         I1 = I - 1
         IC = IWORK( INODE+I1 )
         NL = IWORK( NDIML+I1 )
         NLP1 = NL + 1
         NR = IWORK( NDIMR+I1 )
         NRP1 = NR + 1
         NLF = IC - NL
         NRF = IC + 1
         SQREI = 1
         CALL <a name="DLASDQ.161"></a><a href="dlasdq.f.html#DLASDQ.1">DLASDQ</a>( <span class="string">'U'</span>, SQREI, NL, NLP1, NL, NCC, D( NLF ), E( NLF ),
     $                VT( NLF, NLF ), LDVT, U( NLF, NLF ), LDU,
     $                U( NLF, NLF ), LDU, WORK, INFO )
         IF( INFO.NE.0 ) THEN
            RETURN
         END IF
         ITEMP = IDXQ + NLF - 2
         DO 10 J = 1, NL
            IWORK( ITEMP+J ) = J
   10    CONTINUE
         IF( I.EQ.ND ) THEN
            SQREI = SQRE
         ELSE
            SQREI = 1
         END IF
         NRP1 = NR + SQREI
         CALL <a name="DLASDQ.177"></a><a href="dlasdq.f.html#DLASDQ.1">DLASDQ</a>( <span class="string">'U'</span>, SQREI, NR, NRP1, NR, NCC, D( NRF ), E( NRF ),
     $                VT( NRF, NRF ), LDVT, U( NRF, NRF ), LDU,
     $                U( NRF, NRF ), LDU, WORK, INFO )
         IF( INFO.NE.0 ) THEN
            RETURN
         END IF
         ITEMP = IDXQ + IC
         DO 20 J = 1, NR
            IWORK( ITEMP+J-1 ) = J
   20    CONTINUE
   30 CONTINUE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Now conquer each subproblem bottom-up.
</span><span class="comment">*</span><span class="comment">
</span>      DO 50 LVL = NLVL, 1, -1
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Find the first node LF and last node LL on the
</span><span class="comment">*</span><span class="comment">        current level LVL.
</span><span class="comment">*</span><span class="comment">
</span>         IF( LVL.EQ.1 ) THEN
            LF = 1
            LL = 1
         ELSE
            LF = 2**( LVL-1 )
            LL = 2*LF - 1
         END IF
         DO 40 I = LF, LL
            IM1 = I - 1
            IC = IWORK( INODE+IM1 )
            NL = IWORK( NDIML+IM1 )
            NR = IWORK( NDIMR+IM1 )
            NLF = IC - NL
            IF( ( SQRE.EQ.0 ) .AND. ( I.EQ.LL ) ) THEN
               SQREI = SQRE
            ELSE
               SQREI = 1
            END IF
            IDXQC = IDXQ + NLF - 1
            ALPHA = D( IC )
            BETA = E( IC )
            CALL <a name="DLASD1.217"></a><a href="dlasd1.f.html#DLASD1.1">DLASD1</a>( NL, NR, SQREI, D( NLF ), ALPHA, BETA,
     $                   U( NLF, NLF ), LDU, VT( NLF, NLF ), LDVT,
     $                   IWORK( IDXQC ), IWORK( IWK ), WORK, INFO )
            IF( INFO.NE.0 ) THEN
               RETURN
            END IF
   40    CONTINUE
   50 CONTINUE
<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="DLASD0.228"></a><a href="dlasd0.f.html#DLASD0.1">DLASD0</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

</pre>

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