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来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 334 行 · 第 1/2 页

<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Set up the start point in X if the increment is not unity. This
</span><span class="comment">*</span><span class="comment">     will be  ( N - 1 )*INCX  too small for descending loops.
</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 A.
</span><span class="comment">*</span><span class="comment">
</span>      IF (<a name="LSAME.162"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(TRANS,<span class="string">'N'</span>)) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Form  x := A*x.
</span><span class="comment">*</span><span class="comment">
</span>          IF (<a name="LSAME.166"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'U'</span>)) THEN
              IF (INCX.EQ.1) THEN
                  DO 20 J = 1,N
                      IF (X(J).NE.ZERO) THEN
                          TEMP = X(J)
                          DO 10 I = 1,J - 1
                              X(I) = X(I) + TEMP*A(I,J)
   10                     CONTINUE
                          IF (NOUNIT) X(J) = X(J)*A(J,J)
                      END IF
   20             CONTINUE
              ELSE
                  JX = KX
                  DO 40 J = 1,N
                      IF (X(JX).NE.ZERO) THEN
                          TEMP = X(JX)
                          IX = KX
                          DO 30 I = 1,J - 1
                              X(IX) = X(IX) + TEMP*A(I,J)
                              IX = IX + INCX
   30                     CONTINUE
                          IF (NOUNIT) X(JX) = X(JX)*A(J,J)
                      END IF
                      JX = JX + INCX
   40             CONTINUE
              END IF
          ELSE
              IF (INCX.EQ.1) THEN
                  DO 60 J = N,1,-1
                      IF (X(J).NE.ZERO) THEN
                          TEMP = X(J)
                          DO 50 I = N,J + 1,-1
                              X(I) = X(I) + TEMP*A(I,J)
   50                     CONTINUE
                          IF (NOUNIT) X(J) = X(J)*A(J,J)
                      END IF
   60             CONTINUE
              ELSE
                  KX = KX + (N-1)*INCX
                  JX = KX
                  DO 80 J = N,1,-1
                      IF (X(JX).NE.ZERO) THEN
                          TEMP = X(JX)
                          IX = KX
                          DO 70 I = N,J + 1,-1
                              X(IX) = X(IX) + TEMP*A(I,J)
                              IX = IX - INCX
   70                     CONTINUE
                          IF (NOUNIT) X(JX) = X(JX)*A(J,J)
                      END IF
                      JX = JX - INCX
   80             CONTINUE
              END IF
          END IF
      ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Form  x := A'*x  or  x := conjg( A' )*x.
</span><span class="comment">*</span><span class="comment">
</span>          IF (<a name="LSAME.224"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'U'</span>)) THEN
              IF (INCX.EQ.1) THEN
                  DO 110 J = N,1,-1
                      TEMP = X(J)
                      IF (NOCONJ) THEN
                          IF (NOUNIT) TEMP = TEMP*A(J,J)
                          DO 90 I = J - 1,1,-1
                              TEMP = TEMP + A(I,J)*X(I)
   90                     CONTINUE
                      ELSE
                          IF (NOUNIT) TEMP = TEMP*DCONJG(A(J,J))
                          DO 100 I = J - 1,1,-1
                              TEMP = TEMP + DCONJG(A(I,J))*X(I)
  100                     CONTINUE
                      END IF
                      X(J) = TEMP
  110             CONTINUE
              ELSE
                  JX = KX + (N-1)*INCX
                  DO 140 J = N,1,-1
                      TEMP = X(JX)
                      IX = JX
                      IF (NOCONJ) THEN
                          IF (NOUNIT) TEMP = TEMP*A(J,J)
                          DO 120 I = J - 1,1,-1
                              IX = IX - INCX
                              TEMP = TEMP + A(I,J)*X(IX)
  120                     CONTINUE
                      ELSE
                          IF (NOUNIT) TEMP = TEMP*DCONJG(A(J,J))
                          DO 130 I = J - 1,1,-1
                              IX = IX - INCX
                              TEMP = TEMP + DCONJG(A(I,J))*X(IX)
  130                     CONTINUE
                      END IF
                      X(JX) = TEMP
                      JX = JX - INCX
  140             CONTINUE
              END IF
          ELSE
              IF (INCX.EQ.1) THEN
                  DO 170 J = 1,N
                      TEMP = X(J)
                      IF (NOCONJ) THEN
                          IF (NOUNIT) TEMP = TEMP*A(J,J)
                          DO 150 I = J + 1,N
                              TEMP = TEMP + A(I,J)*X(I)
  150                     CONTINUE
                      ELSE
                          IF (NOUNIT) TEMP = TEMP*DCONJG(A(J,J))
                          DO 160 I = J + 1,N
                              TEMP = TEMP + DCONJG(A(I,J))*X(I)
  160                     CONTINUE
                      END IF
                      X(J) = TEMP
  170             CONTINUE
              ELSE
                  JX = KX
                  DO 200 J = 1,N
                      TEMP = X(JX)
                      IX = JX
                      IF (NOCONJ) THEN
                          IF (NOUNIT) TEMP = TEMP*A(J,J)
                          DO 180 I = J + 1,N
                              IX = IX + INCX
                              TEMP = TEMP + A(I,J)*X(IX)
  180                     CONTINUE
                      ELSE
                          IF (NOUNIT) TEMP = TEMP*DCONJG(A(J,J))
                          DO 190 I = J + 1,N
                              IX = IX + INCX
                              TEMP = TEMP + DCONJG(A(I,J))*X(IX)
  190                     CONTINUE
                      END IF
                      X(JX) = TEMP
                      JX = JX + INCX
  200             CONTINUE
              END IF
          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="ZTRMV.307"></a><a href="ztrmv.f.html#ZTRMV.1">ZTRMV</a> .
</span><span class="comment">*</span><span class="comment">
</span>      END

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