NTL（数论库）中矩阵的空闲内存

Question

各位！我在 SGX 飞地内使用 NTL。当我运行应用程序时，我遇到了有关 out of memory 的问题。然后查了一下内存，估计是大量使用NTL矩阵的缘故。

矩阵在NTL中的基本使用：

Mat<size_t> mtemp;
mtemp.SetDims(num_row, num_col);

在NTL matrix.cpp中，我没有找到任何释放内存的函数。

对于kill()，实现大约是swap():

template<class T>
void Mat<T>::kill()  
{  
   Mat<T> tmp;
   this->swap(tmp);
}  

void swap(Mat& other)
   {
      _mat__rep.swap(other._mat__rep);
      _ntl_swap(_mat__numcols, other._mat__numcols);
   }

template<class T>
void _ntl_swap(T*& a, T*& b)
{
   T* t = a; a = b; b = t;
}

这不能帮助释放矩阵的内存。使用后如何释放内存？

Answer 1

kill() 函数应该可以做到这一点。
假设实现Mat::~Mat()释放内存

template<class T>
void Mat<T>::kill()  
{  
   // This allocates an object with absolute minimum size (probably zero).
   Mat<T> tmp;


   // Now you swap the zero size matrix with your current matrix
   // memory. 
   this->swap(tmp);

   // So your object `this` now holds a zero size matrix.
   // While the object `tmp` holds what used to be in this object.
   // So all the dynamically allocated memory is now inside `tmp`
}
// At this point `tmp` goes out of scope.
// This causes the destructor of `tmp` to be called which
// deallocates the memory that you used to have.
//
// So at this point your object holds a mtrix of zero size.
// and all the old memory has been deallocated.

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