我使用magick ++庫來管理圖像。我想使用openMPI分發我的算法，是否可以發送對象？使用openMPI發送對象
例如在我的代碼，我有
Image image(imgName);
int w = image.columns();
int h = image.rows();
PixelPacket *pixels = image.getPixels(0, 0, w, h);
我可以發送pixels與MPI_SEND或什麼的分散？如果是與哪個數據類型？
一般來說，除非你有一個專門爲你打包的庫，否則在MPI中發送一個專門的對象是不可能的。內置的數據類型的MPI標準列（MPI 3.0 665頁，定義的值和把手有列表），但在較高的水平，他們是：
MPI_CHARMPI_INTMPI_FLOATMPI_DOUBLEMPI_BYTE有比這更多，但其中大部分最終都是這樣的。
您可以將這些類型放在一起製作自己的自定義數據類型。舉例來說，如果你知道你要送一束包含類似結構的：
{
int index;
char[100] name;
double value;
}
您可以構建一個類型來認爲，這將是一個連續的類型，名稱，然後一整體數據類型的結構類型（它將包含int，爲名稱構造的類型和double）。
您只需要創建一個數據類型來描述您的PixelPacket。
我不是C++程序員，但以下是你所要求的。基本上，我開始使用Magick ++開始8 MPI過程（我碰巧使用mpich），主人讀取圖像（Lena當然是從PNG文件），然後將其發送給每個從機。奴隸接收Lena並從他們收到的數據中重建她，並且每個奴隸用不同的名字寫出自己的本地副本作爲JPEG。
我欺騙了尺寸，因爲計算尺寸和傳遞這些尺寸很簡單，但與我所展示的無關。
#include <cstdlib>
#include <iostream>
#include <Magick++.h>
#include "mpi.h"
using namespace std;
int main (int argc, char *argv[])
{
int id,p;
int number;
// Initialise MPI
MPI::Init (argc,argv);
// Initialize ImageMagick and image processing stuff
Magick::InitializeMagick(*argv);
int row,col;
Magick::Image image;
int bytes=512*512*3; // I happen to know Lena is 512x512 and RGB - i.e. 3 bytes/pixel
unsigned char buffer[bytes];
// Get the number of processes
p = MPI::COMM_WORLD.Get_size();
// Get the individual process ID
id = MPI::COMM_WORLD.Get_rank();
// Master will read in Lena and send her to all slaves
if(id==0)
{
cout << "MASTER: The number of processes is " << p << endl;
// Read in Lena and put her in a buffer to send via MPI
image.read("lena.png");
// Convert Lena to a bunch of bytes
image.write(0,0,512,512,"RGB",Magick::CharPixel,buffer);
// Send the luscious Lena to all slaves
for(int z=1;z<p;z++){
cout << "MASTER: Sending Lena to slave " << z << endl;
MPI_Send(buffer,bytes,MPI_BYTE,z,0,MPI_COMM_WORLD);
}
}else{
// All slaves will receive Lena and write her out as a JPEG
cout << "Process:" << id << " Started and waiting for Lena..." << endl;
MPI_Recv(buffer,bytes,MPI_BYTE,0,0,MPI_COMM_WORLD,MPI_STATUS_IGNORE);
cout << "Process:" << id << " Received Lena" << endl;
// Rebuild Lena from the bunch of bytes and write to "Lena-Rebuilt-<id>.jpg"
Magick::Image rebuilt(512,512,"RGB",Magick::CharPixel,buffer);
char filename[100];
sprintf(filename,"Lena-Rebuilt-%d.jpg",id);
rebuilt.write(filename);
}
// Terminate MPI
MPI::Finalize();
return 0;
}
我Makefile看起來是這樣的：
all: main
run: main
mpirun -n 8 ./main
main: main.cpp
mpic++ main.cpp -o main $$(Magick++-config --cxxflags --libs)
它運行是這樣的：
make run
mpirun -n 8 ./main
MASTER: The number of processes is 8
Process:1 Started and waiting for Lena...
Process:3 Started and waiting for Lena...
Process:4 Started and waiting for Lena...
Process:5 Started and waiting for Lena...
Process:7 Started and waiting for Lena...
Process:6 Started and waiting for Lena...
Process:2 Started and waiting for Lena...
MASTER: Sending Lena to slave 1
MASTER: Sending Lena to slave 2
Process:1 Received Lena
MASTER: Sending Lena to slave 3
Process:2 Received Lena
MASTER: Sending Lena to slave 4
Process:3 Received Lena
MASTER: Sending Lena to slave 5
Process:4 Received Lena
MASTER: Sending Lena to slave 6
Process:5 Received Lena
MASTER: Sending Lena to slave 7
Process:6 Received Lena
Process:7 Received Lena
，輸出是這樣的：
[email protected] 1 mark staff 150467 23 Oct 15:34 lena.png
-rw-r--r-- 1 mark staff 1786 23 Oct 17:04 main.cpp
-rwxr-xr-x 1 mark staff 51076 23 Oct 17:14 main
[email protected] 1 mark staff 64755 23 Oct 17:14 Lena-Rebuilt-7.jpg
[email protected] 1 mark staff 64755 23 Oct 17:14 Lena-Rebuilt-6.jpg
[email protected] 1 mark staff 64755 23 Oct 17:14 Lena-Rebuilt-5.jpg
[email protected] 1 mark staff 64755 23 Oct 17:14 Lena-Rebuilt-4.jpg
[email protected] 1 mark staff 64755 23 Oct 17:14 Lena-Rebuilt-3.jpg
[email protected] 1 mark staff 64755 23 Oct 17:14 Lena-Rebuilt-2.jpg
[email protected] 1 mark staff 64755 23 Oct 17:14 Lena-Rebuilt-1.jpg