zspmv.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 289 行 · 第 1/2 页

         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 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><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
      KK = 1
      IF( <a name="LSAME.182"></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 AP contains the 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
               K = KK
               DO 50 I = 1, J - 1
                  Y( I ) = Y( I ) + TEMP1*AP( K )
                  TEMP2 = TEMP2 + AP( K )*X( I )
                  K = K + 1
   50          CONTINUE
               Y( J ) = Y( J ) + TEMP1*AP( KK+J-1 ) + ALPHA*TEMP2
               KK = KK + J
   60       CONTINUE
         ELSE
            JX = KX
            JY = KY
            DO 80 J = 1, N
               TEMP1 = ALPHA*X( JX )
               TEMP2 = ZERO
               IX = KX
               IY = KY
               DO 70 K = KK, KK + J - 2
                  Y( IY ) = Y( IY ) + TEMP1*AP( K )
                  TEMP2 = TEMP2 + AP( K )*X( IX )
                  IX = IX + INCX
                  IY = IY + INCY
   70          CONTINUE
               Y( JY ) = Y( JY ) + TEMP1*AP( KK+J-1 ) + ALPHA*TEMP2
               JX = JX + INCX
               JY = JY + INCY
               KK = KK + J
   80       CONTINUE
         END IF
      ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Form  y  when AP contains the 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*AP( KK )
               K = KK + 1
               DO 90 I = J + 1, N
                  Y( I ) = Y( I ) + TEMP1*AP( K )
                  TEMP2 = TEMP2 + AP( K )*X( I )
                  K = K + 1
   90          CONTINUE
               Y( J ) = Y( J ) + ALPHA*TEMP2
               KK = KK + ( N-J+1 )
  100       CONTINUE
         ELSE
            JX = KX
            JY = KY
            DO 120 J = 1, N
               TEMP1 = ALPHA*X( JX )
               TEMP2 = ZERO
               Y( JY ) = Y( JY ) + TEMP1*AP( KK )
               IX = JX
               IY = JY
               DO 110 K = KK + 1, KK + N - J
                  IX = IX + INCX
                  IY = IY + INCY
                  Y( IY ) = Y( IY ) + TEMP1*AP( K )
                  TEMP2 = TEMP2 + AP( K )*X( IX )
  110          CONTINUE
               Y( JY ) = Y( JY ) + ALPHA*TEMP2
               JX = JX + INCX
               JY = JY + INCY
               KK = KK + ( N-J+1 )
  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="ZSPMV.262"></a><a href="zspmv.f.html#ZSPMV.1">ZSPMV</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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