chpr2.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 277 行 · 第 1/2 页

          INFO = 1
      ELSE IF (N.LT.0) THEN
          INFO = 2
      ELSE IF (INCX.EQ.0) THEN
          INFO = 5
      ELSE IF (INCY.EQ.0) THEN
          INFO = 7
      END IF
      IF (INFO.NE.0) THEN
          CALL <a name="XERBLA.130"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>(<span class="string">'<a name="CHPR2.130"></a><a href="chpr2.f.html#CHPR2.1">CHPR2</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)) 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 if the increments are not both
</span><span class="comment">*</span><span class="comment">     unity.
</span><span class="comment">*</span><span class="comment">
</span>      IF ((INCX.NE.1) .OR. (INCY.NE.1)) THEN
          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
          JX = KX
          JY = KY
      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 the array AP
</span><span class="comment">*</span><span class="comment">     are accessed sequentially with one pass through AP.
</span><span class="comment">*</span><span class="comment">
</span>      KK = 1
      IF (<a name="LSAME.160"></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 upper triangle is stored in AP.
</span><span class="comment">*</span><span class="comment">
</span>          IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
              DO 20 J = 1,N
                  IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN
                      TEMP1 = ALPHA*CONJG(Y(J))
                      TEMP2 = CONJG(ALPHA*X(J))
                      K = KK
                      DO 10 I = 1,J - 1
                          AP(K) = AP(K) + X(I)*TEMP1 + Y(I)*TEMP2
                          K = K + 1
   10                 CONTINUE
                      AP(KK+J-1) = REAL(AP(KK+J-1)) +
     +                             REAL(X(J)*TEMP1+Y(J)*TEMP2)
                  ELSE
                      AP(KK+J-1) = REAL(AP(KK+J-1))
                  END IF
                  KK = KK + J
   20         CONTINUE
          ELSE
              DO 40 J = 1,N
                  IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN
                      TEMP1 = ALPHA*CONJG(Y(JY))
                      TEMP2 = CONJG(ALPHA*X(JX))
                      IX = KX
                      IY = KY
                      DO 30 K = KK,KK + J - 2
                          AP(K) = AP(K) + X(IX)*TEMP1 + Y(IY)*TEMP2
                          IX = IX + INCX
                          IY = IY + INCY
   30                 CONTINUE
                      AP(KK+J-1) = REAL(AP(KK+J-1)) +
     +                             REAL(X(JX)*TEMP1+Y(JY)*TEMP2)
                  ELSE
                      AP(KK+J-1) = REAL(AP(KK+J-1))
                  END IF
                  JX = JX + INCX
                  JY = JY + INCY
                  KK = KK + J
   40         CONTINUE
          END IF
      ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Form  A  when lower triangle is stored in AP.
</span><span class="comment">*</span><span class="comment">
</span>          IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
              DO 60 J = 1,N
                  IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN
                      TEMP1 = ALPHA*CONJG(Y(J))
                      TEMP2 = CONJG(ALPHA*X(J))
                      AP(KK) = REAL(AP(KK)) +
     +                         REAL(X(J)*TEMP1+Y(J)*TEMP2)
                      K = KK + 1
                      DO 50 I = J + 1,N
                          AP(K) = AP(K) + X(I)*TEMP1 + Y(I)*TEMP2
                          K = K + 1
   50                 CONTINUE
                  ELSE
                      AP(KK) = REAL(AP(KK))
                  END IF
                  KK = KK + N - J + 1
   60         CONTINUE
          ELSE
              DO 80 J = 1,N
                  IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN
                      TEMP1 = ALPHA*CONJG(Y(JY))
                      TEMP2 = CONJG(ALPHA*X(JX))
                      AP(KK) = REAL(AP(KK)) +
     +                         REAL(X(JX)*TEMP1+Y(JY)*TEMP2)
                      IX = JX
                      IY = JY
                      DO 70 K = KK + 1,KK + N - J
                          IX = IX + INCX
                          IY = IY + INCY
                          AP(K) = AP(K) + X(IX)*TEMP1 + Y(IY)*TEMP2
   70                 CONTINUE
                  ELSE
                      AP(KK) = REAL(AP(KK))
                  END IF
                  JX = JX + INCX
                  JY = JY + INCY
                  KK = KK + N - J + 1
   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="CHPR2.250"></a><a href="chpr2.f.html#CHPR2.1">CHPR2</a> .
</span><span class="comment">*</span><span class="comment">
</span>      END

</pre>

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