关于数学库中的对齐

╰半夏微凉° 2021-11-01 22:26 328阅读 0赞

在各类数学库中,如DirectXMath,XNA,Eigen等,为了使用SSE加速

往往用\_\_declspec(align(16))定义其向量矩阵,因而对编程产生了一些影响

Eigen的说明文档写的比较详细,列举了以下各类情况,并提供了解决方案,使用其他数学库也可以参考

<table> 
 <tbody> 
  <tr> 
   <td align="right">&nbsp;</td> 
   <td><a href="http://eigen.tuxfamily.org/dox/group__TopicUnalignedArrayAssert.html" rel="nofollow">Explanation of the assertion on unaligned arrays</a></td> 
  </tr> 
  <tr> 
   <td colspan="2">&nbsp;</td> 
  </tr> 
  <tr> 
   <td align="right">&nbsp;</td> 
   <td><a href="http://eigen.tuxfamily.org/dox/group__TopicFixedSizeVectorizable.html" rel="nofollow">Fixed-size vectorizable Eigen objects</a></td> 
  </tr> 
  <tr> 
   <td colspan="2">&nbsp;</td> 
  </tr> 
  <tr> 
   <td align="right">&nbsp;</td> 
   <td><a href="http://eigen.tuxfamily.org/dox/group__TopicStructHavingEigenMembers.html" rel="nofollow">Structures Having Eigen Members</a></td> 
  </tr> 
  <tr> 
   <td colspan="2">&nbsp;</td> 
  </tr> 
  <tr> 
   <td align="right">&nbsp;</td> 
   <td><a href="http://eigen.tuxfamily.org/dox/group__TopicStlContainers.html" rel="nofollow">Using STL Containers with Eigen</a></td> 
  </tr> 
  <tr> 
   <td colspan="2">&nbsp;</td> 
  </tr> 
  <tr> 
   <td align="right">&nbsp;</td> 
   <td><a href="http://eigen.tuxfamily.org/dox/group__TopicPassingByValue.html" rel="nofollow">Passing Eigen objects by value to functions</a></td> 
  </tr> 
  <tr> 
   <td colspan="2">&nbsp;</td> 
  </tr> 
  <tr> 
   <td align="right">&nbsp;</td> 
   <td><a href="http://eigen.tuxfamily.org/dox/group__TopicWrongStackAlignment.html" rel="nofollow">Compiler making a wrong assumption on stack alignment</a></td> 
  </tr> 
 </tbody> 
</table>

仅就我个人使用而言,主要遇到以下两点问题

*  字节对齐的对象作为参数,因为形参不一定是对齐的,所以会造成程序中断,部分编译器也可能直接报错--解决方法很简单,参数设为指针或者引用型参数
 *  类或结构体中包含字节对其的对象--重载new和delete

template<size_t Alignment>
    class CAlignedAllocation
    {
    public:
        static void* operator new(size_t size) { return _aligned_malloc(size, Alignment); }
        static void operator delete(void* memory) { _aligned_free(memory); }
    };
    
    class CMyClass:
    public CAlignedAllocation<16>
    {
      DirectX::XMVector...  
    }

转载于:https://www.cnblogs.com/Foxy-Jo/p/11075005.html