dtpmv.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 315 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 AP are
</span><span class="comment">*</span><span class="comment">     accessed sequentially with one pass through AP.
</span><span class="comment">*</span><span class="comment">
</span>      IF (<a name="LSAME.153"></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.157"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'U'</span>)) THEN
              KK = 1
              IF (INCX.EQ.1) THEN
                  DO 20 J = 1,N
                      IF (X(J).NE.ZERO) THEN
                          TEMP = X(J)
                          K = KK
                          DO 10 I = 1,J - 1
                              X(I) = X(I) + TEMP*AP(K)
                              K = K + 1
   10                     CONTINUE
                          IF (NOUNIT) X(J) = X(J)*AP(KK+J-1)
                      END IF
                      KK = KK + J
   20             CONTINUE
              ELSE
                  JX = KX
                  DO 40 J = 1,N
                      IF (X(JX).NE.ZERO) THEN
                          TEMP = X(JX)
                          IX = KX
                          DO 30 K = KK,KK + J - 2
                              X(IX) = X(IX) + TEMP*AP(K)
                              IX = IX + INCX
   30                     CONTINUE
                          IF (NOUNIT) X(JX) = X(JX)*AP(KK+J-1)
                      END IF
                      JX = JX + INCX
                      KK = KK + J
   40             CONTINUE
              END IF
          ELSE
              KK = (N* (N+1))/2
              IF (INCX.EQ.1) THEN
                  DO 60 J = N,1,-1
                      IF (X(J).NE.ZERO) THEN
                          TEMP = X(J)
                          K = KK
                          DO 50 I = N,J + 1,-1
                              X(I) = X(I) + TEMP*AP(K)
                              K = K - 1
   50                     CONTINUE
                          IF (NOUNIT) X(J) = X(J)*AP(KK-N+J)
                      END IF
                      KK = KK - (N-J+1)
   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 K = KK,KK - (N- (J+1)),-1
                              X(IX) = X(IX) + TEMP*AP(K)
                              IX = IX - INCX
   70                     CONTINUE
                          IF (NOUNIT) X(JX) = X(JX)*AP(KK-N+J)
                      END IF
                      JX = JX - INCX
                      KK = KK - (N-J+1)
   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.
</span><span class="comment">*</span><span class="comment">
</span>          IF (<a name="LSAME.225"></a><a href="lsame.f.html#LSAME.1">LSAME</a>(UPLO,<span class="string">'U'</span>)) THEN
              KK = (N* (N+1))/2
              IF (INCX.EQ.1) THEN
                  DO 100 J = N,1,-1
                      TEMP = X(J)
                      IF (NOUNIT) TEMP = TEMP*AP(KK)
                      K = KK - 1
                      DO 90 I = J - 1,1,-1
                          TEMP = TEMP + AP(K)*X(I)
                          K = K - 1
   90                 CONTINUE
                      X(J) = TEMP
                      KK = KK - J
  100             CONTINUE
              ELSE
                  JX = KX + (N-1)*INCX
                  DO 120 J = N,1,-1
                      TEMP = X(JX)
                      IX = JX
                      IF (NOUNIT) TEMP = TEMP*AP(KK)
                      DO 110 K = KK - 1,KK - J + 1,-1
                          IX = IX - INCX
                          TEMP = TEMP + AP(K)*X(IX)
  110                 CONTINUE
                      X(JX) = TEMP
                      JX = JX - INCX
                      KK = KK - J
  120             CONTINUE
              END IF
          ELSE
              KK = 1
              IF (INCX.EQ.1) THEN
                  DO 140 J = 1,N
                      TEMP = X(J)
                      IF (NOUNIT) TEMP = TEMP*AP(KK)
                      K = KK + 1
                      DO 130 I = J + 1,N
                          TEMP = TEMP + AP(K)*X(I)
                          K = K + 1
  130                 CONTINUE
                      X(J) = TEMP
                      KK = KK + (N-J+1)
  140             CONTINUE
              ELSE
                  JX = KX
                  DO 160 J = 1,N
                      TEMP = X(JX)
                      IX = JX
                      IF (NOUNIT) TEMP = TEMP*AP(KK)
                      DO 150 K = KK + 1,KK + N - J
                          IX = IX + INCX
                          TEMP = TEMP + AP(K)*X(IX)
  150                 CONTINUE
                      X(JX) = TEMP
                      JX = JX + INCX
                      KK = KK + (N-J+1)
  160             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="DTPMV.288"></a><a href="dtpmv.f.html#DTPMV.1">DTPMV</a> .
</span><span class="comment">*</span><span class="comment">
</span>      END

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