zspr.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 238 行 · 第 1/2 页

</span><span class="comment">*</span><span class="comment">     Test the input parameters.
</span><span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( .NOT.<a name="LSAME.104"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> ) .AND. .NOT.<a name="LSAME.104"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> ) ) THEN
         INFO = 1
      ELSE IF( N.LT.0 ) THEN
         INFO = 2
      ELSE IF( INCX.EQ.0 ) THEN
         INFO = 5
      END IF
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.112"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="ZSPR.112"></a><a href="zspr.f.html#ZSPR.1">ZSPR</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 the start point in X if the increment is not unity.
</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 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.133"></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 ) THEN
            DO 20 J = 1, N
               IF( X( J ).NE.ZERO ) THEN
                  TEMP = ALPHA*X( J )
                  K = KK
                  DO 10 I = 1, J - 1
                     AP( K ) = AP( K ) + X( I )*TEMP
                     K = K + 1
   10             CONTINUE
                  AP( KK+J-1 ) = AP( KK+J-1 ) + X( J )*TEMP
               ELSE
                  AP( KK+J-1 ) = 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 = ALPHA*X( JX )
                  IX = KX
                  DO 30 K = KK, KK + J - 2
                     AP( K ) = AP( K ) + X( IX )*TEMP
                     IX = IX + INCX
   30             CONTINUE
                  AP( KK+J-1 ) = AP( KK+J-1 ) + X( JX )*TEMP
               ELSE
                  AP( KK+J-1 ) = AP( KK+J-1 )
               END IF
               JX = JX + INCX
               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 ) THEN
            DO 60 J = 1, N
               IF( X( J ).NE.ZERO ) THEN
                  TEMP = ALPHA*X( J )
                  AP( KK ) = AP( KK ) + TEMP*X( J )
                  K = KK + 1
                  DO 50 I = J + 1, N
                     AP( K ) = AP( K ) + X( I )*TEMP
                     K = K + 1
   50             CONTINUE
               ELSE
                  AP( KK ) = AP( KK )
               END IF
               KK = KK + N - J + 1
   60       CONTINUE
         ELSE
            JX = KX
            DO 80 J = 1, N
               IF( X( JX ).NE.ZERO ) THEN
                  TEMP = ALPHA*X( JX )
                  AP( KK ) = AP( KK ) + TEMP*X( JX )
                  IX = JX
                  DO 70 K = KK + 1, KK + N - J
                     IX = IX + INCX
                     AP( K ) = AP( K ) + X( IX )*TEMP
   70             CONTINUE
               ELSE
                  AP( KK ) = AP( KK )
               END IF
               JX = JX + INCX
               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="ZSPR.211"></a><a href="zspr.f.html#ZSPR.1">ZSPR</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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