ssbevx.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 440 行 · 第 1/3 页

      IF( ANRM.GT.ZERO .AND. ANRM.LT.RMIN ) THEN
         ISCALE = 1
         SIGMA = RMIN / ANRM
      ELSE IF( ANRM.GT.RMAX ) THEN
         ISCALE = 1
         SIGMA = RMAX / ANRM
      END IF
      IF( ISCALE.EQ.1 ) THEN
         IF( LOWER ) THEN
            CALL <a name="SLASCL.285"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>( <span class="string">'B'</span>, KD, KD, ONE, SIGMA, N, N, AB, LDAB, INFO )
         ELSE
            CALL <a name="SLASCL.287"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>( <span class="string">'Q'</span>, KD, KD, ONE, SIGMA, N, N, AB, LDAB, INFO )
         END IF
         IF( ABSTOL.GT.0 )
     $      ABSTLL = ABSTOL*SIGMA
         IF( VALEIG ) THEN
            VLL = VL*SIGMA
            VUU = VU*SIGMA
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Call <a name="SSBTRD.297"></a><a href="ssbtrd.f.html#SSBTRD.1">SSBTRD</a> to reduce symmetric band matrix to tridiagonal form.
</span><span class="comment">*</span><span class="comment">
</span>      INDD = 1
      INDE = INDD + N
      INDWRK = INDE + N
      CALL <a name="SSBTRD.302"></a><a href="ssbtrd.f.html#SSBTRD.1">SSBTRD</a>( JOBZ, UPLO, N, KD, AB, LDAB, WORK( INDD ),
     $             WORK( INDE ), Q, LDQ, WORK( INDWRK ), IINFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     If all eigenvalues are desired and ABSTOL is less than or equal
</span><span class="comment">*</span><span class="comment">     to zero, then call <a name="SSTERF.306"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a> or <a name="SSTEQR.306"></a><a href="ssteqr.f.html#SSTEQR.1">SSTEQR</a>.  If this fails for some
</span><span class="comment">*</span><span class="comment">     eigenvalue, then try <a name="SSTEBZ.307"></a><a href="sstebz.f.html#SSTEBZ.1">SSTEBZ</a>.
</span><span class="comment">*</span><span class="comment">
</span>      TEST = .FALSE.
      IF (INDEIG) THEN
         IF (IL.EQ.1 .AND. IU.EQ.N) THEN
            TEST = .TRUE.
         END IF
      END IF
      IF ((ALLEIG .OR. TEST) .AND. (ABSTOL.LE.ZERO)) THEN
         CALL SCOPY( N, WORK( INDD ), 1, W, 1 )
         INDEE = INDWRK + 2*N
         IF( .NOT.WANTZ ) THEN
            CALL SCOPY( N-1, WORK( INDE ), 1, WORK( INDEE ), 1 )
            CALL <a name="SSTERF.320"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>( N, W, WORK( INDEE ), INFO )
         ELSE
            CALL <a name="SLACPY.322"></a><a href="slacpy.f.html#SLACPY.1">SLACPY</a>( <span class="string">'A'</span>, N, N, Q, LDQ, Z, LDZ )
            CALL SCOPY( N-1, WORK( INDE ), 1, WORK( INDEE ), 1 )
            CALL <a name="SSTEQR.324"></a><a href="ssteqr.f.html#SSTEQR.1">SSTEQR</a>( JOBZ, N, W, WORK( INDEE ), Z, LDZ,
     $                   WORK( INDWRK ), INFO )
            IF( INFO.EQ.0 ) THEN
               DO 10 I = 1, N
                  IFAIL( I ) = 0
   10          CONTINUE
            END IF
         END IF
         IF( INFO.EQ.0 ) THEN
            M = N
            GO TO 30
         END IF
         INFO = 0
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Otherwise, call <a name="SSTEBZ.339"></a><a href="sstebz.f.html#SSTEBZ.1">SSTEBZ</a> and, if eigenvectors are desired, <a name="SSTEIN.339"></a><a href="sstein.f.html#SSTEIN.1">SSTEIN</a>.
</span><span class="comment">*</span><span class="comment">
</span>      IF( WANTZ ) THEN
         ORDER = <span class="string">'B'</span>
      ELSE
         ORDER = <span class="string">'E'</span>
      END IF
      INDIBL = 1
      INDISP = INDIBL + N
      INDIWO = INDISP + N
      CALL <a name="SSTEBZ.349"></a><a href="sstebz.f.html#SSTEBZ.1">SSTEBZ</a>( RANGE, ORDER, N, VLL, VUU, IL, IU, ABSTLL,
     $             WORK( INDD ), WORK( INDE ), M, NSPLIT, W,
     $             IWORK( INDIBL ), IWORK( INDISP ), WORK( INDWRK ),
     $             IWORK( INDIWO ), INFO )
<span class="comment">*</span><span class="comment">
</span>      IF( WANTZ ) THEN
         CALL <a name="SSTEIN.355"></a><a href="sstein.f.html#SSTEIN.1">SSTEIN</a>( N, WORK( INDD ), WORK( INDE ), M, W,
     $                IWORK( INDIBL ), IWORK( INDISP ), Z, LDZ,
     $                WORK( INDWRK ), IWORK( INDIWO ), IFAIL, INFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Apply orthogonal matrix used in reduction to tridiagonal
</span><span class="comment">*</span><span class="comment">        form to eigenvectors returned by <a name="SSTEIN.360"></a><a href="sstein.f.html#SSTEIN.1">SSTEIN</a>.
</span><span class="comment">*</span><span class="comment">
</span>         DO 20 J = 1, M
            CALL SCOPY( N, Z( 1, J ), 1, WORK( 1 ), 1 )
            CALL SGEMV( <span class="string">'N'</span>, N, N, ONE, Q, LDQ, WORK, 1, ZERO,
     $                  Z( 1, J ), 1 )
   20    CONTINUE
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     If matrix was scaled, then rescale eigenvalues appropriately.
</span><span class="comment">*</span><span class="comment">
</span>   30 CONTINUE
      IF( ISCALE.EQ.1 ) THEN
         IF( INFO.EQ.0 ) THEN
            IMAX = M
         ELSE
            IMAX = INFO - 1
         END IF
         CALL SSCAL( IMAX, ONE / SIGMA, W, 1 )
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     If eigenvalues are not in order, then sort them, along with
</span><span class="comment">*</span><span class="comment">     eigenvectors.
</span><span class="comment">*</span><span class="comment">
</span>      IF( WANTZ ) THEN
         DO 50 J = 1, M - 1
            I = 0
            TMP1 = W( J )
            DO 40 JJ = J + 1, M
               IF( W( JJ ).LT.TMP1 ) THEN
                  I = JJ
                  TMP1 = W( JJ )
               END IF
   40       CONTINUE
<span class="comment">*</span><span class="comment">
</span>            IF( I.NE.0 ) THEN
               ITMP1 = IWORK( INDIBL+I-1 )
               W( I ) = W( J )
               IWORK( INDIBL+I-1 ) = IWORK( INDIBL+J-1 )
               W( J ) = TMP1
               IWORK( INDIBL+J-1 ) = ITMP1
               CALL SSWAP( N, Z( 1, I ), 1, Z( 1, J ), 1 )
               IF( INFO.NE.0 ) THEN
                  ITMP1 = IFAIL( I )
                  IFAIL( I ) = IFAIL( J )
                  IFAIL( J ) = ITMP1
               END IF
            END IF
   50    CONTINUE
      END IF
<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="SSBEVX.413"></a><a href="ssbevx.f.html#SSBEVX.1">SSBEVX</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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