設置置換陣列

嘿，我有設定MPI_IScatterv置換陣列（）函數的一個問題。設置置換陣列

我需要撒圖片的部分不同的進程。我已經作出了自己的MPI_Datatype：

private: MPI_Datatype createMPI_PixelType(){ 
MPI_Datatype new_type; 

int count = 3; 
int blocklens[] = { 1,1,1 }; 

MPI_Aint indices[3]; 
indices[0] = (MPI_Aint)offsetof(struct Pixel, Red); 
indices[1] = (MPI_Aint)offsetof(struct Pixel, Green); 
indices[2] = (MPI_Aint)offsetof(struct Pixel, Blue); 

MPI_Datatype old_types[] = { MPI_INT, MPI_INT, MPI_INT }; 

MPI_Type_create_struct(count, blocklens, indices, old_types, &new_type); 
MPI_Type_commit(&new_type); 

return new_type;}

結構像素的

struct Pixel { 
int Red; 
int Green; 
int Blue; }

因爲函數參數我需要通過置換陣列。我對它的理解是，每個進程都從指定爲disp [proc_id]的不同位置開始讀取sendBuffer。例如進程0 DISP = 0，過程1個DISP = 0的sizeof元件，過程2 = DISP的sizeof 1 + 0元件等這裏是代碼

... 
    //specify arrays for scathering 
    sendCountArray = calcSendCounts(workTable); 
    displacementArray = calcDisplacementArray(workTable); 

    Pixel *fullPicture = pictureToPixelsArray(); 
    cout << endl; 
    for (int i = 0; i < pixelsOnPicture; i++) { 
     cout << 
      " r:" << fullPicture[i].Red << 
      " g:" << fullPicture[i].Green << 
      " b:" << fullPicture[i].Blue << endl; 
    } 

    cout << endl << "sendArray:" << endl; 
    for (int i = 0; i < worldSize; i++) { 
     cout << "i:" << i << " " << sendCountArray[i] << endl; 
    } 
    cout << endl << "displacementArray:" << endl; 
    for (int i = 0; i < worldSize; i++) { 
     cout << "i:" << i << " " << displacementArray[i] << endl; 
    } 
} 
cout << endl; 
// 
MPI_Scatter(sendCountArray, 1, MPI_INT, &pixelsSizeBuffer, 1, MPI_INT, 0, MPI_COMM_WORLD); 

//sending part of picture 
MPI_Request request; 
MPI_Datatype mMPI_PIXEL = createMPI_PixelType(); 
partPicture = new Pixel[pixelsSizeBuffer]; 
MPI_Iscatterv(pictureToPixelsArray(), sendCountArray, displacementArray, mMPI_PIXEL, partPicture, pixelsSizeBuffer, mMPI_PIXEL, 0, MPI_COMM_WORLD, &request); 
for (int i = 0; i < pixelsSizeBuffer; i++) { 
    cout << "proc:" << procID << 
     " r:" << partPicture[i].Red << 
     " g:" << partPicture[i].Green << 
     " b:" << partPicture[i].Blue << endl; 
}

和這裏正在測試輸出（6個處理）

pixelsOnPicture:9 
workTableSize: 6 

r:255 g:242 b:0 
r:63 g:72 b:204 
r:237 g:28 b:36 
r:0 g:162 b:232 
r:163 g:73 b:164 
r:63 g:11 b:15 
r:34 g:177 b:76 
r:255 g:242 b:0 
r:63 g:10 b:16 

sendArray: 
i:0 2 
i:1 2 
i:2 2 
i:3 1 
i:4 1 
i:5 1 

displacementArray: 
i:0 0 
i:1 2 
i:2 4 
i:3 6 
i:4 7 
i:5 8 

proc:4 r:-842150451 g:-842150451 b:-842150451 
proc:0 r:255 g:242 b:0 
proc:2 r:-842150451 g:-842150451 b:-842150451 
proc:5 r:-842150451 g:-842150451 b:-842150451 
proc:0 r:63 g:72 b:204 
proc:2 r:-842150451 g:-842150451 b:-842150451 
proc:1 r:-842150451 g:-842150451 b:-842150451 
proc:3 r:-842150451 g:-842150451 b:-842150451 
proc:1 r:-842150451 g:-842150451 b:-842150451

第2個元件被正確地發送..

來源

2016-04-24 Phatee P

您還沒有嬌嬌要求所以不能保證Iscatterv在您檢查輸出點完成。調用普通的舊Scatterv將確保調用完成後，您將能夠檢查是否已正確設置所有參數和數據類型。或調用Iscatterv後面加一個MPI_WAIT（&要求），但要知道，你在這裏所做的一切是爲了重新實現阻塞調用。

來源

2016-04-26 17:30:13

設置置換陣列

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