zgeesx.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 409 行 · 第 1/3 页

</span><span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.0 ) THEN
         SDIM = 0
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Get machine constants
</span><span class="comment">*</span><span class="comment">
</span>      EPS = <a name="DLAMCH.264"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'P'</span> )
      SMLNUM = <a name="DLAMCH.265"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'S'</span> )
      BIGNUM = ONE / SMLNUM
      CALL <a name="DLABAD.267"></a><a href="dlabad.f.html#DLABAD.1">DLABAD</a>( SMLNUM, BIGNUM )
      SMLNUM = SQRT( SMLNUM ) / EPS
      BIGNUM = ONE / SMLNUM
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Scale A if max element outside range [SMLNUM,BIGNUM]
</span><span class="comment">*</span><span class="comment">
</span>      ANRM = <a name="ZLANGE.273"></a><a href="zlange.f.html#ZLANGE.1">ZLANGE</a>( <span class="string">'M'</span>, N, N, A, LDA, DUM )
      SCALEA = .FALSE.
      IF( ANRM.GT.ZERO .AND. ANRM.LT.SMLNUM ) THEN
         SCALEA = .TRUE.
         CSCALE = SMLNUM
      ELSE IF( ANRM.GT.BIGNUM ) THEN
         SCALEA = .TRUE.
         CSCALE = BIGNUM
      END IF
      IF( SCALEA )
     $   CALL <a name="ZLASCL.283"></a><a href="zlascl.f.html#ZLASCL.1">ZLASCL</a>( <span class="string">'G'</span>, 0, 0, ANRM, CSCALE, N, N, A, LDA, IERR )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Permute the matrix to make it more nearly triangular
</span><span class="comment">*</span><span class="comment">     (CWorkspace: none)
</span><span class="comment">*</span><span class="comment">     (RWorkspace: need N)
</span><span class="comment">*</span><span class="comment">
</span>      IBAL = 1
      CALL <a name="ZGEBAL.291"></a><a href="zgebal.f.html#ZGEBAL.1">ZGEBAL</a>( <span class="string">'P'</span>, N, A, LDA, ILO, IHI, RWORK( IBAL ), IERR )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Reduce to upper Hessenberg form
</span><span class="comment">*</span><span class="comment">     (CWorkspace: need 2*N, prefer N+N*NB)
</span><span class="comment">*</span><span class="comment">     (RWorkspace: none)
</span><span class="comment">*</span><span class="comment">
</span>      ITAU = 1
      IWRK = N + ITAU
      CALL <a name="ZGEHRD.299"></a><a href="zgehrd.f.html#ZGEHRD.1">ZGEHRD</a>( N, ILO, IHI, A, LDA, WORK( ITAU ), WORK( IWRK ),
     $             LWORK-IWRK+1, IERR )
<span class="comment">*</span><span class="comment">
</span>      IF( WANTVS ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Copy Householder vectors to VS
</span><span class="comment">*</span><span class="comment">
</span>         CALL <a name="ZLACPY.306"></a><a href="zlacpy.f.html#ZLACPY.1">ZLACPY</a>( <span class="string">'L'</span>, N, N, A, LDA, VS, LDVS )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Generate unitary matrix in VS
</span><span class="comment">*</span><span class="comment">        (CWorkspace: need 2*N-1, prefer N+(N-1)*NB)
</span><span class="comment">*</span><span class="comment">        (RWorkspace: none)
</span><span class="comment">*</span><span class="comment">
</span>         CALL <a name="ZUNGHR.312"></a><a href="zunghr.f.html#ZUNGHR.1">ZUNGHR</a>( N, ILO, IHI, VS, LDVS, WORK( ITAU ), WORK( IWRK ),
     $                LWORK-IWRK+1, IERR )
      END IF
<span class="comment">*</span><span class="comment">
</span>      SDIM = 0
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Perform QR iteration, accumulating Schur vectors in VS if desired
</span><span class="comment">*</span><span class="comment">     (CWorkspace: need 1, prefer HSWORK (see comments) )
</span><span class="comment">*</span><span class="comment">     (RWorkspace: none)
</span><span class="comment">*</span><span class="comment">
</span>      IWRK = ITAU
      CALL <a name="ZHSEQR.323"></a><a href="zhseqr.f.html#ZHSEQR.1">ZHSEQR</a>( <span class="string">'S'</span>, JOBVS, N, ILO, IHI, A, LDA, W, VS, LDVS,
     $             WORK( IWRK ), LWORK-IWRK+1, IEVAL )
      IF( IEVAL.GT.0 )
     $   INFO = IEVAL
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Sort eigenvalues if desired
</span><span class="comment">*</span><span class="comment">
</span>      IF( WANTST .AND. INFO.EQ.0 ) THEN
         IF( SCALEA )
     $      CALL <a name="ZLASCL.332"></a><a href="zlascl.f.html#ZLASCL.1">ZLASCL</a>( <span class="string">'G'</span>, 0, 0, CSCALE, ANRM, N, 1, W, N, IERR )
         DO 10 I = 1, N
            BWORK( I ) = SELECT( W( I ) )
   10    CONTINUE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Reorder eigenvalues, transform Schur vectors, and compute
</span><span class="comment">*</span><span class="comment">        reciprocal condition numbers
</span><span class="comment">*</span><span class="comment">        (CWorkspace: if SENSE is not 'N', need 2*SDIM*(N-SDIM)
</span><span class="comment">*</span><span class="comment">                     otherwise, need none )
</span><span class="comment">*</span><span class="comment">        (RWorkspace: none)
</span><span class="comment">*</span><span class="comment">
</span>         CALL <a name="ZTRSEN.343"></a><a href="ztrsen.f.html#ZTRSEN.1">ZTRSEN</a>( SENSE, JOBVS, BWORK, N, A, LDA, VS, LDVS, W, SDIM,
     $                RCONDE, RCONDV, WORK( IWRK ), LWORK-IWRK+1,
     $                ICOND )
         IF( .NOT.WANTSN )
     $      MAXWRK = MAX( MAXWRK, 2*SDIM*( N-SDIM ) )
         IF( ICOND.EQ.-14 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Not enough complex workspace
</span><span class="comment">*</span><span class="comment">
</span>            INFO = -15
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( WANTVS ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Undo balancing
</span><span class="comment">*</span><span class="comment">        (CWorkspace: none)
</span><span class="comment">*</span><span class="comment">        (RWorkspace: need N)
</span><span class="comment">*</span><span class="comment">
</span>         CALL <a name="ZGEBAK.362"></a><a href="zgebak.f.html#ZGEBAK.1">ZGEBAK</a>( <span class="string">'P'</span>, <span class="string">'R'</span>, N, ILO, IHI, RWORK( IBAL ), N, VS, LDVS,
     $                IERR )
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( SCALEA ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Undo scaling for the Schur form of A
</span><span class="comment">*</span><span class="comment">
</span>         CALL <a name="ZLASCL.370"></a><a href="zlascl.f.html#ZLASCL.1">ZLASCL</a>( <span class="string">'U'</span>, 0, 0, CSCALE, ANRM, N, N, A, LDA, IERR )
         CALL ZCOPY( N, A, LDA+1, W, 1 )
         IF( ( WANTSV .OR. WANTSB ) .AND. INFO.EQ.0 ) THEN
            DUM( 1 ) = RCONDV
            CALL <a name="DLASCL.374"></a><a href="dlascl.f.html#DLASCL.1">DLASCL</a>( <span class="string">'G'</span>, 0, 0, CSCALE, ANRM, 1, 1, DUM, 1, IERR )
            RCONDV = DUM( 1 )
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      WORK( 1 ) = MAXWRK
      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="ZGEESX.382"></a><a href="zgeesx.f.html#ZGEESX.1">ZGEESX</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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