c++ cuda:构造函数之外的cudaMallocManaged访问

Question

我有一个c++类，它像这样使用cudaMallocManaged：

MyMatrix::MyMatrix(int new_rows, int new_cols, int padrr, int padcc)
{
  rows = new_rows;
  cols = new_cols;
  padr = padrr;
  padc = padcc;

  cout << "allocating memory" << endl;
  float *data;
  cudaError_t cudaStatus = cudaMallocManaged(&data, new_rows*new_cols*sizeof(float));
  if (cudaStatus != cudaSuccess){
      cout << cudaStatus << endl << flush;
      exit(1);
  }
  cudaDeviceSynchronize();
  cout << "allocating memory successful:" << cudaStatus << endl;
  // I CAN ACCESS DATA HERE
  //data[15] = 5.5; //fine
}
MyMatrix::~MyMatrix(void)
{
 cudaFree(data); // delete the data array
}

我也有一个头.h文件：

class MyMatrix
{

  public:
      MyMatrix(int new_rows, int new_cols, int padr, int padt);
      ~MyMatrix(void);

      float *data;
      int padr;
      int padc;
      int rows;
      int cols;
}

我可以很好地访问这个构造函数中的数据数组。

然而，一旦我试图访问它(读或写)在它之外，我就会得到terminated by signal SIGSEGV (Address boundary error)。例如：

MyMatrix *newmat = new MyMatrix(totalr, totalc, padr, padc);
cout << (*newmat).data[0] << endl;

或

MyMatrix newmat = new MyMatrix(totalr, totalc, padr, padc);
cout << newmat.data[0] << endl;

我如何“坚持”这个指针？

Answer 1

在构造函数中创建一个名为data的局部变量。

float *data;

在分配库达内存并将值分配给局部变量data之后，内存地址似乎不会永久存储在任何地方。所以，你的记忆就变得遥不可及。

您有这一行newmat.data，但在构造中，您从未将任何值分配给成员data。您确实使用了同名的局部变量。

Answer 2

你的问题是

MyMatrix::MyMatrix(int new_rows, int new_cols, int padrr, int padcc)
{
  rows = new_rows;
  cols = new_cols;
  padr = padrr;
  padc = padcc;

  cout << "allocating memory" << endl;
  float *data;
  cudaError_t cudaStatus = cudaMallocManaged(&data, new_rows*new_cols*sizeof(float));
  if (cudaStatus != cudaSuccess){
      cout << cudaStatus << endl << flush;
      exit(1);
  }
  cudaDeviceSynchronize();
  cout << "allocating memory successful:" << cudaStatus << endl;
  // I CAN ACCESS DATA HERE
  //data[15] = 5.5; //fine
}

您在cudaMallocManaged(&data, new_rows*new_cols*sizeof(float))中使用的cudaMallocManaged(&data, new_rows*new_cols*sizeof(float))是您在上面一行中声明的float *data;，而不是类的data成员。只需去掉本地float *data;，就可以使用data类成员，如

MyMatrix::MyMatrix(int new_rows, int new_cols, int padrr, int padcc)
{
  rows = new_rows;
  cols = new_cols;
  padr = padrr;
  padc = padcc;

  cout << "allocating memory" << endl;

  cudaError_t cudaStatus = cudaMallocManaged(&data, new_rows*new_cols*sizeof(float));
  if (cudaStatus != cudaSuccess){
      cout << cudaStatus << endl << flush;
      exit(1);
  }
  cudaDeviceSynchronize();
  cout << "allocating memory successful:" << cudaStatus << endl;
  // I CAN ACCESS DATA HERE
  //data[15] = 5.5; //fine
}