MPI-IO 只写入一个进程的数据

Question

出于某种原因，MPI-IO 仅将我的一个进程中的数据写入文件。我用MPI_File_open打开文件，MPI_File_set_view设置每个进程的视图，MPI_File_write_all写出数据。当我运行代码时，一切似乎都执行得很好并且没有任何错误，但是由于某种原因，文件输出包含 CSV 文件第一行的乱码垃圾（它只是说 NULL NULL NULL 一堆和当我打开它以在 VS Code 中阅读时，在第一行不断重复），文件的其余部分是第二个进程块的输出（因为我在两个进程上使用块分解）。我似乎无法弄清楚为什么我的程序没有正确输出值（或者至少是第一个过程），我想我会在这里问。

我在这里附上了代码并省略了不适用于手头问题的部分：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include <time.h>
#include <mpi.h>


int main (int argc, char** argv) {

    int iproc, nproc;
    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &iproc);
    MPI_Comm_size(MPI_COMM_WORLD, &nproc);

    //Inputs:
    int depth = 3;
    float p_x_error = 0.05;
    float p_z_error = 0.05;

    int max_char[] = {128, 640, 328};
    int i_max_char = max_char[(depth%3)];

    int num_data_qubits = depth * depth;
    int data_qubit_x_error[ depth + 2][ depth + 2 ];
    int data_qubit_z_error[ depth + 2  ][ depth + 2 ];
    int ancilla_qubit_value[ depth + 1 ][ depth + 1 ];

    // Parallel block decomposition variables
    int total_num_iter = pow(4, num_data_qubits);           // Total number of outer loop iterations
    int block_size = floor(total_num_iter/nproc);       // Number of iterations per process (block)

    if (total_num_iter%nproc > 0) { block_size += 1; }  // Add 1 if blocks don't divide evenly

    int iter_first = iproc * block_size;
    int iter_last = iter_first + block_size;

    MPI_Status status;
    MPI_File fh;

    char buf[i_max_char];

    //Output:
    MPI_File_open(MPI_COMM_SELF, "testfile.csv", MPI_MODE_CREATE | MPI_MODE_WRONLY, MPI_INFO_NULL, &fh);
    MPI_File_set_view(fh, iproc * block_size * strlen(buf) * sizeof(char), MPI_CHAR, MPI_CHAR, "native", MPI_INFO_NULL);

    if(iproc == 0) {
        printf("Block size: %d\n", block_size);
    }

    for ( int i = iter_first; i < iter_last; i++ ) {

        // A bunch of stuff happens where values are written to the 2d arrays listed above

        char label_list[i_max_char];
        strcpy(label_list, "\n");
        char anc_name[3];

        // Output the ancilla qubit values in proper format
        int ancilla_value;
        for (int k=1; k < depth; k++) {
            if (k%2 == 0) {
                ancilla_value = (ancilla_qubit_value[depth][k] == 1) ? -1 : 1;
                sprintf(anc_name, "%d,", ancilla_value);
                strcat(label_list, anc_name);
            }
            for (int j=depth-1; j > 0; j--) {
                if (k == 1 && j%2 == 0) {
                    ancilla_value = (ancilla_qubit_value[j][k-1] == 1) ? -1 : 1;
                    sprintf(anc_name, "%d,", ancilla_value);
                    strcat(label_list, anc_name);
                } else if (k == (depth - 1) && j%2 == 1) {
                    ancilla_value = (ancilla_qubit_value[j][k+1] == 1) ? -1 : 1;
                    sprintf(anc_name, "%d,", ancilla_value);
                    strcat(label_list, anc_name);
                }
                ancilla_value = (ancilla_qubit_value[j][k] == 1) ? -1 : 1;
                sprintf(anc_name, "%d,", ancilla_value);
                strcat(label_list, anc_name);
            }
            if (k%2 == 1) {
                ancilla_value = (ancilla_qubit_value[0][k] == 1) ? -1 : 1;
                sprintf(anc_name, "%d,", ancilla_value);
                strcat(label_list, anc_name);
            }
        }

        // For printing label list:
        strcat(label_list, "\"[");
        char qubit_name[6];
        int first = 1;

        for (int k = 1; k < depth + 1; k++) {
            for (int j = depth; j > 0; j--) {
                if (data_qubit_x_error[j][k] == 1) {
                    if (first == 1) {
                        first = 0;
                    } else {
                        strcat(label_list, ", ");
                    }
                    sprintf(qubit_name, "'X%d%d'", (k-1), (depth-j));
                    strcat(label_list, qubit_name);
                }
                if (data_qubit_z_error[j][k] == 1) {
                    if (first == 1) {
                        first = 0;
                    } else {
                        strcat(label_list, ", ");
                    }
                    sprintf(qubit_name, "'Z%d%d'", (k-1), (depth-j));
                    strcat(label_list, qubit_name);
                }
            }
        }
        strcat(label_list, "]\"");

        MPI_File_write_all(fh, label_list, strlen(label_list) * sizeof(char), MPI_CHAR, MPI_STATUS_IGNORE);

    }

    MPI_File_close(&fh);
    MPI_Finalize();
    return 0;
}

Answer 1

经过大量挖掘，我终于找到了答案。我用作 MPI_File_set_view() 偏移量的值是用 strlen(buf) 测量 buf 的大小为 1，因为变量已初始化，但未填充。我通过将偏移值更改为 (MPI_Offset) (iproc * block_size * i_max_char) 来解决这个问题，这样偏移量就会是正确的长度，这似乎已经解决了这个问题！

MPI-IO 只写入一个进程的数据

MPI-IO only writes data from one process

c

mpi

mpi-io