zher.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 239 行 · 第 1/2 页

</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL <a name="XERBLA.103"></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 DBLE,DCONJG,MAX
<span class="comment">*</span><span class="comment">     ..
</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>      INFO = 0
      IF (.NOT.<a name="LSAME.112"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'U'</span>) .AND. .NOT.<a name="LSAME.112"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'L'</span>)) THEN
          INFO = 1
      ELSE IF (N.LT.0) THEN
          INFO = 2
      ELSE IF (INCX.EQ.0) THEN
          INFO = 5
      ELSE IF (LDA.LT.MAX(1,N)) THEN
          INFO = 7
      END IF
      IF (INFO.NE.0) THEN
          CALL <a name="XERBLA.122"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>(<span class="string">'<a name="ZHER.122"></a><a href="zher.f.html#ZHER.1">ZHER</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>      IF ((N.EQ.0) .OR. (ALPHA.EQ.DBLE(ZERO))) RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Set the start point in X if the increment is not unity.
</span><span class="comment">*</span><span class="comment">
</span>      IF (INCX.LE.0) THEN
          KX = 1 - (N-1)*INCX
      ELSE IF (INCX.NE.1) THEN
          KX = 1
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Start the operations. In this version the elements of A are
</span><span class="comment">*</span><span class="comment">     accessed sequentially with one pass through the triangular part
</span><span class="comment">*</span><span class="comment">     of A.
</span><span class="comment">*</span><span class="comment">
</span>      IF (<a name="LSAME.142"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'U'</span>)) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Form  A  when A is stored in upper triangle.
</span><span class="comment">*</span><span class="comment">
</span>          IF (INCX.EQ.1) THEN
              DO 20 J = 1,N
                  IF (X(J).NE.ZERO) THEN
                      TEMP = ALPHA*DCONJG(X(J))
                      DO 10 I = 1,J - 1
                          A(I,J) = A(I,J) + X(I)*TEMP
   10                 CONTINUE
                      A(J,J) = DBLE(A(J,J)) + DBLE(X(J)*TEMP)
                  ELSE
                      A(J,J) = DBLE(A(J,J))
                  END IF
   20         CONTINUE
          ELSE
              JX = KX
              DO 40 J = 1,N
                  IF (X(JX).NE.ZERO) THEN
                      TEMP = ALPHA*DCONJG(X(JX))
                      IX = KX
                      DO 30 I = 1,J - 1
                          A(I,J) = A(I,J) + X(IX)*TEMP
                          IX = IX + INCX
   30                 CONTINUE
                      A(J,J) = DBLE(A(J,J)) + DBLE(X(JX)*TEMP)
                  ELSE
                      A(J,J) = DBLE(A(J,J))
                  END IF
                  JX = JX + INCX
   40         CONTINUE
          END IF
      ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Form  A  when A is stored in lower triangle.
</span><span class="comment">*</span><span class="comment">
</span>          IF (INCX.EQ.1) THEN
              DO 60 J = 1,N
                  IF (X(J).NE.ZERO) THEN
                      TEMP = ALPHA*DCONJG(X(J))
                      A(J,J) = DBLE(A(J,J)) + DBLE(TEMP*X(J))
                      DO 50 I = J + 1,N
                          A(I,J) = A(I,J) + X(I)*TEMP
   50                 CONTINUE
                  ELSE
                      A(J,J) = DBLE(A(J,J))
                  END IF
   60         CONTINUE
          ELSE
              JX = KX
              DO 80 J = 1,N
                  IF (X(JX).NE.ZERO) THEN
                      TEMP = ALPHA*DCONJG(X(JX))
                      A(J,J) = DBLE(A(J,J)) + DBLE(TEMP*X(JX))
                      IX = JX
                      DO 70 I = J + 1,N
                          IX = IX + INCX
                          A(I,J) = A(I,J) + X(IX)*TEMP
   70                 CONTINUE
                  ELSE
                      A(J,J) = DBLE(A(J,J))
                  END IF
                  JX = JX + INCX
   80         CONTINUE
          END IF
      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="ZHER.212"></a><a href="zher.f.html#ZHER.1">ZHER</a>  .
</span><span class="comment">*</span><span class="comment">
</span>      END

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