OpenACC的 - 私人2D陣列

Question

我處理塊對角矩陣（每個塊具有相同的尺寸），並且我有一個illegal address error當我使用private動態分配的2D陣列...

// NB is the number of block 
// N is the block size 
// A is the main matrix (block diagonal) 

double** B; // a block 
B = new double*[N]; 
for (unsigned int i = 0; i < N; i++) 
    B[i] = new double[N]; 

#pragma acc parallel loop private(B[:N][:N]) copyin(A[:NB*N][:NB*N]) 
for (unsigned int b = 0; b < NB; b++) { 
    #pragma acc loop 
    for (unsigned int i = 0; i < N; i++) { 
     #pragma acc loop 
     for (unsigned int j = 0; j < N; j++) { 
      B[i][j] = A[b*N+i][b*N+j]; 
     } 
    } 
    // process B 
} 

for (unsigned int i = 0; i < N; i++) 
    delete[] B[i]; 
delete[] B; 

錯誤我得到的是：

call to cuStreamSynchronize returned error 700: Illegal address during kernel execution 

如果我陣列壓扁成一維數組，並使用詞典的索引或靜態二維數組，但我使用需要double**作爲參數的函數，所以我寧願堅持使用動態2D它工作正常數組...

我已經閱讀了關於在規範的private條款，但它並沒有說，動態二維數組，不支持，所以我想我做錯了什麼......

Answer 1

很抱歉，但使用不支持私有子句中的指針數組。問題在於，編譯器運行時必須爲每個組，工作者或向量動態創建一個私有（取決於使用私有子句的循環）並填寫所有設備指針。這會帶來非常高的間接費用。

如果「B」是一個固定大小的靜態數組，「double B [N] [N]」，那麼你可以在private子句中使用它。

否則，我會建議通過添加第三維手動私有化數組。

// NB is the number of block 
// N is the block size 
// A is the main matrix (block diagonal) 

double*** B; // a block 
B = new double**[NB]; 
for (unsigned int i = 0; i < NB; i++) { 
    B[i] = new double*[N]; 
    for (unsigned int j = 0; j < N; j++) { 
    B[i][j] = new double[N]; 
}} 


#pragma acc parallel loop create(B[:NB][:N][:N]) copyin(A[:NB*N][:NB*N]) 
for (unsigned int b = 0; b < NB; b++) { 
    #pragma acc loop 
    for (unsigned int i = 0; i < N; i++) { 
     #pragma acc loop 
     for (unsigned int j = 0; j < N; j++) { 
      B[b][i][j] = A[b*N+i][b*N+j]; 
     } 
    } 
    // process B 
} 

for (unsigned int i = 0; i < NB; i++) { 
    for (unsigned int j = 0; j < N; j++) { 
    delete[] B[i][j]; 
    } 
    delete[] B[i]; 
} 
delete[] B;