MPI IO当不知道偏移量时写入文件 [英] MPI IO Writing a file when offset is not known

问题描述

我想使用MPI IO写入文件. 进程处于while循环中，它调用一个函数，该函数生成随机量的数据.我想将此数据写入单个文件. 我该怎么做?

I want to use MPI IO to write files. The processes is in a while loop and it calls a function which generates random amount of data. I want to write this data to a single file. How can I accomplish this?

推荐答案

在while循环的每次迭代中，每个进程都知道将要写入多少数据.使用MPI_SCAN共享该数据，然后使用MPI_File_write_at_all进行集体写入:

in each iteration of your while loop, each process knows how much data will be written. Use MPI_SCAN to share that data, then MPI_File_write_at_all to write collectively:

      incr = generate_random_data();
      MPI_Scan(&incr, &new_offset, 1, MPI_LONG_LONG_INT, 
                      MPI_SUM, MPI_COMM_WORLD);
      new_offset -= incr;

      ret = MPI_File_write_at_all(mpi_fh, new_offset, buf, count,
                              datatype, status);

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