OpenMP的生命遊戲

Question

我做了一個生命遊戲的順序版本，但現在我需要使用OpenMP創建一個並行版本的代碼，但我遇到了一些問題。 如果有人能幫助我，那將會非常好。 THKS。 這裏是我的順序代碼：

// Swapping the two grids 
#define SWAP_BOARDS(b1, b2) do { \ 
char* temp = b1; \ 
b1 = b2; \ 
b2 = temp; \ 
} while(0) 

// Simplifying access to grid elements 
    #define BOARD(G, X, Y) ((G)[NC*(X)+(Y)]) 

char* sequential_game_of_life (char* outgrid, char* ingrid, 
     const int nrows, const int ncols, const int gens_max) { 

    const int NC = ncols; 
    int curgen, i, j; 

for (curgen = 0; curgen < gens_max; curgen++) 
    { 

    for (i = 0; i < nrows; i++) 
{ 
    for (j = 0; j < ncols; j++) 
    { 
     const int inorth = mod (i-1, nrows); 
     const int isouth = mod (i+1, nrows); 
     const int jwest = mod (j-1, ncols); 
     const int jeast = mod (j+1, ncols); 

     const char neighbor_count = 
    BOARD (ingrid, inorth, jwest) + 
    BOARD (ingrid, inorth, j) + 
    BOARD (ingrid, inorth, jeast) + 
    BOARD (ingrid, i, jwest) + 
    BOARD (ingrid, i, jeast) + 
    BOARD (ingrid, isouth, jwest) + 
    BOARD (ingrid, isouth, j) + 
    BOARD (ingrid, isouth, jeast); 

     BOARD(outgrid, i, j) = alivep (neighbor_count, BOARD (ingrid, i, j)); 
    } 
} 
    SWAP_BOARDS(outgrid, ingrid); 
} 
    return outgrid; 
} 

我知道，我必須爲平行的那些3，但我不能看到如何做到這一點。

Answer 1

我覺得外環不能並行，因爲輸入到每一代前代，所以它有一個順序式（至少你不能用細微的變化做到這一點！）

在的情況下，嵌套循環遍歷矩陣或類似的東西，我喜歡從0到ncol*nrow（在你的情況）運行一個循環，並從循環索引中找到i和j。

這樣的：

// because you are running a parallel codes multiple times in a loop, 
// it would be better to make the thread swarm first and schedule the 
// tasks in each loop iteration, to avoid multiple creation and destruction 
// of working threads 
#pragma omp parallel 
for (curgen = 0; curgen < gens_max; curgen++) 
{ 
    #pragma omp for 
    for (t = 0; t < nrows*ncols; t++) 
    { 
     int i = t/ncols; 
     int j = t % ncols; 
     const int inorth = mod (i-1, nrows); 
     const int isouth = mod (i+1, nrows); 
     const int jwest = mod (j-1, ncols); 
     const int jeast = mod (j+1, ncols); 

     const char neighbor_count = 
      BOARD (ingrid, inorth, jwest) + 
      BOARD (ingrid, inorth, j) + 
      BOARD (ingrid, inorth, jeast) + 
      BOARD (ingrid, i, jwest) + 
      BOARD (ingrid, i, jeast) + 
      BOARD (ingrid, isouth, jwest) + 
      BOARD (ingrid, isouth, j) + 
      BOARD (ingrid, isouth, jeast); 

     BOARD(outgrid, i, j) = alivep (neighbor_count, BOARD (ingrid, i, j)); 
    } 
    SWAP_BOARDS(outgrid, ingrid); 
} 

我跑在我的筆記本電腦上的1000×1000矩陣雙核2.53 GHz的CPU超過1000代這個代碼，並獲得69％的速度了。