zhpevx.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 413 行 · 第 1/2 页

         IF( VALEIG ) THEN
            IF( N.GT.0 .AND. VU.LE.VL )
     $         INFO = -7
         ELSE IF( INDEIG ) THEN
            IF( IL.LT.1 .OR. IL.GT.MAX( 1, N ) ) THEN
               INFO = -8
            ELSE IF( IU.LT.MIN( N, IL ) .OR. IU.GT.N ) THEN
               INFO = -9
            END IF
         END IF
      END IF
      IF( INFO.EQ.0 ) THEN
         IF( LDZ.LT.1 .OR. ( WANTZ .AND. LDZ.LT.N ) )
     $      INFO = -14
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.206"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="ZHPEVX.206"></a><a href="zhpevx.f.html#ZHPEVX.1">ZHPEVX</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>      M = 0
      IF( N.EQ.0 )
     $   RETURN
<span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.1 ) THEN
         IF( ALLEIG .OR. INDEIG ) THEN
            M = 1
            W( 1 ) = AP( 1 )
         ELSE
            IF( VL.LT.DBLE( AP( 1 ) ) .AND. VU.GE.DBLE( AP( 1 ) ) ) THEN
               M = 1
               W( 1 ) = AP( 1 )
            END IF
         END IF
         IF( WANTZ )
     $      Z( 1, 1 ) = CONE
         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>      SAFMIN = <a name="DLAMCH.233"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'Safe minimum'</span> )
      EPS = <a name="DLAMCH.234"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'Precision'</span> )
      SMLNUM = SAFMIN / EPS
      BIGNUM = ONE / SMLNUM
      RMIN = SQRT( SMLNUM )
      RMAX = MIN( SQRT( BIGNUM ), ONE / SQRT( SQRT( SAFMIN ) ) )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Scale matrix to allowable range, if necessary.
</span><span class="comment">*</span><span class="comment">
</span>      ISCALE = 0
      ABSTLL = ABSTOL
      IF( VALEIG ) THEN
         VLL = VL
         VUU = VU
      ELSE
         VLL = ZERO
         VUU = ZERO
      END IF
      ANRM = <a name="ZLANHP.251"></a><a href="zlanhp.f.html#ZLANHP.1">ZLANHP</a>( <span class="string">'M'</span>, UPLO, N, AP, RWORK )
      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
         CALL ZDSCAL( ( N*( N+1 ) ) / 2, SIGMA, AP, 1 )
         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="ZHPTRD.269"></a><a href="zhptrd.f.html#ZHPTRD.1">ZHPTRD</a> to reduce Hermitian packed matrix to tridiagonal form.
</span><span class="comment">*</span><span class="comment">
</span>      INDD = 1
      INDE = INDD + N
      INDRWK = INDE + N
      INDTAU = 1
      INDWRK = INDTAU + N
      CALL <a name="ZHPTRD.276"></a><a href="zhptrd.f.html#ZHPTRD.1">ZHPTRD</a>( UPLO, N, AP, RWORK( INDD ), RWORK( INDE ),
     $             WORK( INDTAU ), 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="DSTERF.280"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a> or <a name="ZUPGTR.280"></a><a href="zupgtr.f.html#ZUPGTR.1">ZUPGTR</a> and <a name="ZSTEQR.280"></a><a href="zsteqr.f.html#ZSTEQR.1">ZSTEQR</a>.  If this fails
</span><span class="comment">*</span><span class="comment">     for some eigenvalue, then try <a name="DSTEBZ.281"></a><a href="dstebz.f.html#DSTEBZ.1">DSTEBZ</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 DCOPY( N, RWORK( INDD ), 1, W, 1 )
         INDEE = INDRWK + 2*N
         IF( .NOT.WANTZ ) THEN
            CALL DCOPY( N-1, RWORK( INDE ), 1, RWORK( INDEE ), 1 )
            CALL <a name="DSTERF.294"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>( N, W, RWORK( INDEE ), INFO )
         ELSE
            CALL <a name="ZUPGTR.296"></a><a href="zupgtr.f.html#ZUPGTR.1">ZUPGTR</a>( UPLO, N, AP, WORK( INDTAU ), Z, LDZ,
     $                   WORK( INDWRK ), IINFO )
            CALL DCOPY( N-1, RWORK( INDE ), 1, RWORK( INDEE ), 1 )
            CALL <a name="ZSTEQR.299"></a><a href="zsteqr.f.html#ZSTEQR.1">ZSTEQR</a>( JOBZ, N, W, RWORK( INDEE ), Z, LDZ,
     $                   RWORK( INDRWK ), 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 20
         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="DSTEBZ.314"></a><a href="dstebz.f.html#DSTEBZ.1">DSTEBZ</a> and, if eigenvectors are desired, <a name="ZSTEIN.314"></a><a href="zstein.f.html#ZSTEIN.1">ZSTEIN</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
      INDIWK = INDISP + N
      CALL <a name="DSTEBZ.324"></a><a href="dstebz.f.html#DSTEBZ.1">DSTEBZ</a>( RANGE, ORDER, N, VLL, VUU, IL, IU, ABSTLL,
     $             RWORK( INDD ), RWORK( INDE ), M, NSPLIT, W,
     $             IWORK( INDIBL ), IWORK( INDISP ), RWORK( INDRWK ),
     $             IWORK( INDIWK ), INFO )
<span class="comment">*</span><span class="comment">
</span>      IF( WANTZ ) THEN
         CALL <a name="ZSTEIN.330"></a><a href="zstein.f.html#ZSTEIN.1">ZSTEIN</a>( N, RWORK( INDD ), RWORK( INDE ), M, W,
     $                IWORK( INDIBL ), IWORK( INDISP ), Z, LDZ,
     $                RWORK( INDRWK ), IWORK( INDIWK ), IFAIL, INFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Apply unitary matrix used in reduction to tridiagonal
</span><span class="comment">*</span><span class="comment">        form to eigenvectors returned by <a name="ZSTEIN.335"></a><a href="zstein.f.html#ZSTEIN.1">ZSTEIN</a>.
</span><span class="comment">*</span><span class="comment">
</span>         INDWRK = INDTAU + N
         CALL <a name="ZUPMTR.338"></a><a href="zupmtr.f.html#ZUPMTR.1">ZUPMTR</a>( <span class="string">'L'</span>, UPLO, <span class="string">'N'</span>, N, M, AP, WORK( INDTAU ), Z, LDZ,
     $                WORK( INDWRK ), INFO )
      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>   20 CONTINUE
      IF( ISCALE.EQ.1 ) THEN
         IF( INFO.EQ.0 ) THEN
            IMAX = M
         ELSE
            IMAX = INFO - 1
         END IF
         CALL DSCAL( 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 40 J = 1, M - 1
            I = 0
            TMP1 = W( J )
            DO 30 JJ = J + 1, M
               IF( W( JJ ).LT.TMP1 ) THEN
                  I = JJ
                  TMP1 = W( JJ )
               END IF
   30       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 ZSWAP( 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
   40    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="ZHPEVX.386"></a><a href="zhpevx.f.html#ZHPEVX.1">ZHPEVX</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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