c++ - 如何使用 strip 化算法读取 residence.dat 文件 C++

Question

我必须从两个 .dat 文件中读取数据，但是我的控制台输出函数有问题，而且我的 C++ 技能仍然生疏，有人可以帮忙吗？

Read a subset of the address records from residences.dat using striping. For n >processes, each process evaluates a unique subset of records based on every nth record. The number of records in this subset should be approximately #-of-residence-records /#-of-processes. Across all the parallel processes used no address should be omitted and >none should be processed more than once. Also note that only ONE record at a time should be stored in memory by any process; don’t read the entire dataset into a data structure in memory since this is entirely unnecessary and consumes too much RAM!

数据示例

329267.349 4847214.382
318141.019 4851350.892
319526.06 4850474.347
322666.48 4840244.995
316578.529 4837299.827
320090.607 4840439.088



    //read file and populate the vectors


     ifstream foodbankFile("/Users/abdallaelnajjar/Documents/XCodeProjects/cpp_projects/MPI_Project2/foodbanks.dat");
        ifstream residenceFile("/Users/abdallaelnajjar/Documents/XCodeProjects/cpp_projects/MPI_Project2/residences.dat");

        // populate datavector
       std::vector<Foodbank> foodbankData((std::istream_iterator<Foodbank>(foodbankFile)),
                                      std::istream_iterator<Foodbank>());
       //std::vector<Residence> residenceData((std::istream_iterator<Residence>(residenceFile)),
                                      //std::istream_iterator<Residence>());


        std::vector<double> distancess;


        string file_contents;
        Residence res;
        int numProcs = 1;
        int recCount = 0;



    //pseudo code that I trying to implement 
    // While(there are more records){
   // If record count % numProcs == myID
    //   ProcessRecord
   // else
    //   Increment file stream pointer forward one record without processing
   // Increment Record Count
    //}

          int numLines = 1;
        while(!residenceFile.eof())
        {


            residenceFile >> res.x >>res.y;

            //distancess.push_back(populate_distancesVector(res,foodbankData));
            if ( recCount % numProcs == numLines)
            {
                //call the  process
                distancess.push_back(populate_distancesVector(res,foodbankData));
            }
            else
                ++numLines;
            ++recCount;
        }

Answer 1

您很可能得不到任何结果，因为您的文件没有被打开。很可能，您在初始化 fstream 时没有正确指向它.这就是您看不到任何输出的原因。

在对它们进行任何其他操作之前，您应该始终检查您的流是否打开(可访问)。要检查它是否已正确打开:

if (foodBankData.is_open()) {
    Foodbank f;

    while(foodbankData >> f.x >> f.y )
    {
        cout<< "X"<< f.x << "Y" <<f.y << endl; //don't forget the newline here
    }
}
else {
    cerr << "Error opening input file!" << endl;
    exit(1);//call the error function or something else here.
}