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来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 291 行 · 第 1/2 页

      ELSE IF (N.LT.0) THEN
          INFO = 2
      ELSE IF (LDA.LT.MAX(1,N)) THEN
          INFO = 5
      ELSE IF (INCX.EQ.0) THEN
          INFO = 7
      ELSE IF (INCY.EQ.0) THEN
          INFO = 10
      END IF
      IF (INFO.NE.0) THEN
          CALL <a name="XERBLA.138"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>(<span class="string">'<a name="CHEMV.138"></a><a href="chemv.f.html#CHEMV.1">CHEMV</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.ZERO).AND. (BETA.EQ.ONE))) RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Set up the start points in  X  and  Y.
</span><span class="comment">*</span><span class="comment">
</span>      IF (INCX.GT.0) THEN
          KX = 1
      ELSE
          KX = 1 - (N-1)*INCX
      END IF
      IF (INCY.GT.0) THEN
          KY = 1
      ELSE
          KY = 1 - (N-1)*INCY
      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><span class="comment">*</span><span class="comment">     First form  y := beta*y.
</span><span class="comment">*</span><span class="comment">
</span>      IF (BETA.NE.ONE) THEN
          IF (INCY.EQ.1) THEN
              IF (BETA.EQ.ZERO) THEN
                  DO 10 I = 1,N
                      Y(I) = ZERO
   10             CONTINUE
              ELSE
                  DO 20 I = 1,N
                      Y(I) = BETA*Y(I)
   20             CONTINUE
              END IF
          ELSE
              IY = KY
              IF (BETA.EQ.ZERO) THEN
                  DO 30 I = 1,N
                      Y(IY) = ZERO
                      IY = IY + INCY
   30             CONTINUE
              ELSE
                  DO 40 I = 1,N
                      Y(IY) = BETA*Y(IY)
                      IY = IY + INCY
   40             CONTINUE
              END IF
          END IF
      END IF
      IF (ALPHA.EQ.ZERO) RETURN
      IF (<a name="LSAME.192"></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  y  when A is stored in upper triangle.
</span><span class="comment">*</span><span class="comment">
</span>          IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
              DO 60 J = 1,N
                  TEMP1 = ALPHA*X(J)
                  TEMP2 = ZERO
                  DO 50 I = 1,J - 1
                      Y(I) = Y(I) + TEMP1*A(I,J)
                      TEMP2 = TEMP2 + CONJG(A(I,J))*X(I)
   50             CONTINUE
                  Y(J) = Y(J) + TEMP1*REAL(A(J,J)) + ALPHA*TEMP2
   60         CONTINUE
          ELSE
              JX = KX
              JY = KY
              DO 80 J = 1,N
                  TEMP1 = ALPHA*X(JX)
                  TEMP2 = ZERO
                  IX = KX
                  IY = KY
                  DO 70 I = 1,J - 1
                      Y(IY) = Y(IY) + TEMP1*A(I,J)
                      TEMP2 = TEMP2 + CONJG(A(I,J))*X(IX)
                      IX = IX + INCX
                      IY = IY + INCY
   70             CONTINUE
                  Y(JY) = Y(JY) + TEMP1*REAL(A(J,J)) + ALPHA*TEMP2
                  JX = JX + INCX
                  JY = JY + INCY
   80         CONTINUE
          END IF
      ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Form  y  when A is stored in lower triangle.
</span><span class="comment">*</span><span class="comment">
</span>          IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
              DO 100 J = 1,N
                  TEMP1 = ALPHA*X(J)
                  TEMP2 = ZERO
                  Y(J) = Y(J) + TEMP1*REAL(A(J,J))
                  DO 90 I = J + 1,N
                      Y(I) = Y(I) + TEMP1*A(I,J)
                      TEMP2 = TEMP2 + CONJG(A(I,J))*X(I)
   90             CONTINUE
                  Y(J) = Y(J) + ALPHA*TEMP2
  100         CONTINUE
          ELSE
              JX = KX
              JY = KY
              DO 120 J = 1,N
                  TEMP1 = ALPHA*X(JX)
                  TEMP2 = ZERO
                  Y(JY) = Y(JY) + TEMP1*REAL(A(J,J))
                  IX = JX
                  IY = JY
                  DO 110 I = J + 1,N
                      IX = IX + INCX
                      IY = IY + INCY
                      Y(IY) = Y(IY) + TEMP1*A(I,J)
                      TEMP2 = TEMP2 + CONJG(A(I,J))*X(IX)
  110             CONTINUE
                  Y(JY) = Y(JY) + ALPHA*TEMP2
                  JX = JX + INCX
                  JY = JY + INCY
  120         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="CHEMV.264"></a><a href="chemv.f.html#CHEMV.1">CHEMV</a> .
</span><span class="comment">*</span><span class="comment">
</span>      END

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