ssygv.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 254 行 · 第 1/2 页

</span>      REAL               ONE
      PARAMETER          ( ONE = 1.0E+0 )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      LOGICAL            LQUERY, UPPER, WANTZ
      CHARACTER          TRANS
      INTEGER            LWKMIN, LWKOPT, NB, NEIG
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.118"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      INTEGER            <a name="ILAENV.119"></a><a href="hfy-index.html#ILAENV">ILAENV</a>
      EXTERNAL           <a name="ILAENV.120"></a><a href="hfy-index.html#ILAENV">ILAENV</a>, <a name="LSAME.120"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           <a name="SPOTRF.123"></a><a href="spotrf.f.html#SPOTRF.1">SPOTRF</a>, <a name="SSYEV.123"></a><a href="ssyev.f.html#SSYEV.1">SSYEV</a>, <a name="SSYGST.123"></a><a href="ssygst.f.html#SSYGST.1">SSYGST</a>, STRMM, STRSM, <a name="XERBLA.123"></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          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>      WANTZ = <a name="LSAME.132"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'V'</span> )
      UPPER = <a name="LSAME.133"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> )
      LQUERY = ( LWORK.EQ.-1 )
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( ITYPE.LT.1 .OR. ITYPE.GT.3 ) THEN
         INFO = -1
      ELSE IF( .NOT.( WANTZ .OR. <a name="LSAME.139"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'N'</span> ) ) ) THEN
         INFO = -2
      ELSE IF( .NOT.( UPPER .OR. <a name="LSAME.141"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> ) ) ) THEN
         INFO = -3
      ELSE IF( N.LT.0 ) THEN
         INFO = -4
      ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
         INFO = -6
      ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
         INFO = -8
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.EQ.0 ) THEN
         LWKMIN = MAX( 1, 3*N - 1 )
         NB = <a name="ILAENV.153"></a><a href="hfy-index.html#ILAENV">ILAENV</a>( 1, <span class="string">'<a name="SSYTRD.153"></a><a href="ssytrd.f.html#SSYTRD.1">SSYTRD</a>'</span>, UPLO, N, -1, -1, -1 )
         LWKOPT = MAX( LWKMIN, ( NB + 2 )*N )
         WORK( 1 ) = LWKOPT
<span class="comment">*</span><span class="comment">
</span>         IF( LWORK.LT.LWKMIN .AND. .NOT.LQUERY ) THEN
            INFO = -11
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.163"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="SSYGV.163"></a><a href="ssygv.f.html#SSYGV.1">SSYGV</a> '</span>, -INFO )
         RETURN
      ELSE IF( LQUERY ) THEN
         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>      IF( N.EQ.0 )
     $   RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Form a Cholesky factorization of B.
</span><span class="comment">*</span><span class="comment">
</span>      CALL <a name="SPOTRF.176"></a><a href="spotrf.f.html#SPOTRF.1">SPOTRF</a>( UPLO, N, B, LDB, INFO )
      IF( INFO.NE.0 ) THEN
         INFO = N + INFO
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Transform problem to standard eigenvalue problem and solve.
</span><span class="comment">*</span><span class="comment">
</span>      CALL <a name="SSYGST.184"></a><a href="ssygst.f.html#SSYGST.1">SSYGST</a>( ITYPE, UPLO, N, A, LDA, B, LDB, INFO )
      CALL <a name="SSYEV.185"></a><a href="ssyev.f.html#SSYEV.1">SSYEV</a>( JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, INFO )
<span class="comment">*</span><span class="comment">
</span>      IF( WANTZ ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Backtransform eigenvectors to the original problem.
</span><span class="comment">*</span><span class="comment">
</span>         NEIG = N
         IF( INFO.GT.0 )
     $      NEIG = INFO - 1
         IF( ITYPE.EQ.1 .OR. ITYPE.EQ.2 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           For A*x=(lambda)*B*x and A*B*x=(lambda)*x;
</span><span class="comment">*</span><span class="comment">           backtransform eigenvectors: x = inv(L)'*y or inv(U)*y
</span><span class="comment">*</span><span class="comment">
</span>            IF( UPPER ) THEN
               TRANS = <span class="string">'N'</span>
            ELSE
               TRANS = <span class="string">'T'</span>
            END IF
<span class="comment">*</span><span class="comment">
</span>            CALL STRSM( <span class="string">'Left'</span>, UPLO, TRANS, <span class="string">'Non-unit'</span>, N, NEIG, ONE,
     $                  B, LDB, A, LDA )
<span class="comment">*</span><span class="comment">
</span>         ELSE IF( ITYPE.EQ.3 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           For B*A*x=(lambda)*x;
</span><span class="comment">*</span><span class="comment">           backtransform eigenvectors: x = L*y or U'*y
</span><span class="comment">*</span><span class="comment">
</span>            IF( UPPER ) THEN
               TRANS = <span class="string">'T'</span>
            ELSE
               TRANS = <span class="string">'N'</span>
            END IF
<span class="comment">*</span><span class="comment">
</span>            CALL STRMM( <span class="string">'Left'</span>, UPLO, TRANS, <span class="string">'Non-unit'</span>, N, NEIG, ONE,
     $                  B, LDB, A, LDA )
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      WORK( 1 ) = LWKOPT
      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="SSYGV.227"></a><a href="ssygv.f.html#SSYGV.1">SSYGV</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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