我想在进程之间传输一个结构,为此我试图创建一个MPI结构。代码用于蚁群优化(ACO)算法。
C结构的头文件包含:

    #include <stdio.h>
    #include <stdlib.h>
    #include <sys/time.h>
    #include <math.h>
    #include <mpi.h>

    /* Constants */
    #define NUM_CITIES 100      // Number of cities
    //among others

    typedef struct {
        int city, next_city, tabu[NUM_CITIES], path[NUM_CITIES], path_index;
        double tour_distance;
    } ACO_Ant;

我试图按照this thread中的建议构建代码。
程序代码:
    int main(int argc, char *argv[])
    {
    MPI_Datatype MPI_TABU, MPI_PATH, MPI_ANT;

    // Initialize MPI
    MPI_Init(&argc, &argv);
    //Determines the size (&procs) of the group associated with a communicator (MPI_COMM_WORLD)
    MPI_Comm_size(MPI_COMM_WORLD, &procs);
    //Determines the rank (&rank) of the calling process in the communicator (MPI_COMM_WORLD)
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

    MPI_Type_contiguous(NUM_CITIES, MPI_INT, &MPI_TABU);
    MPI_Type_contiguous(NUM_CITIES, MPI_INT, &MPI_PATH);
    MPI_Type_commit(&MPI_TABU);
    MPI_Type_commit(&MPI_PATH);

    // Create ant struct
    //int city, next_city, tabu[NUM_CITIES], path[NUM_CITIES], path_index;
    //double tour_distance;
    int blocklengths[6] = {1,1, NUM_CITIES, NUM_CITIES, 1, 1};
    MPI_Datatype    types[6] = {MPI_INT, MPI_INT, MPI_TABU, MPI_PATH, MPI_INT, MPI_DOUBLE};
    MPI_Aint        offsets[6] = { offsetof( ACO_Ant, city ), offsetof( ACO_Ant, next_city), offsetof( ACO_Ant, tabu), offsetof( ACO_Ant, path ), offsetof( ACO_Ant, path_index ), offsetof( ACO_Ant, tour_distance )};

    MPI_Datatype tmp_type;
    MPI_Aint lb, extent;

    MPI_Type_create_struct(6, blocklengths, offsets, types, &tmp_type);
    MPI_Type_get_extent( tmp_type, &lb, &extent );
    //Tried all of these
    MPI_Type_create_resized( tmp_type, lb, extent, &MPI_ANT );
    //MPI_Type_create_resized( tmp_type, 0, sizeof(MPI_ANT), &MPI_ANT );
    //MPI_Type_create_resized( tmp_type, 0, sizeof(ant), &MPI_ANT );
    MPI_Type_commit(&MPI_ANT);

    printf("Return: %d\n" , MPI_Bcast(ant, NUM_ANTS, MPI_ANT, 0, MPI_COMM_WORLD));
    }

但一旦程序到达MPI_Bcast命令,它就会崩溃,错误代码为11,我认为MPI_ERR_TOPOLOGYas per this manual.是segfault(信号11)。
我也不确定为什么原始程序的作者-
有人能解释他们为什么
MPI_Aint displacements[3];
MPI_Datatype typelist[3];

当结构有两个变量时,大小为3?
int block_lengths[2];

代码:
    void ACO_Build_best(ACO_Best_tour *tour, MPI_Datatype *mpi_type /*out*/)
    {
        int block_lengths[2];
        MPI_Aint displacements[3];
        MPI_Datatype typelist[3];
        MPI_Aint start_address;
        MPI_Aint address;

        block_lengths[0] = 1;
        block_lengths[1] = NUM_CITIES;

        typelist[0] = MPI_DOUBLE;
        typelist[1] = MPI_INT;

        displacements[0] = 0;

        MPI_Address(&(tour->distance), &start_address);
        MPI_Address(tour->path, &address);
        displacements[1] = address - start_address;

        MPI_Type_struct(2, block_lengths, displacements, typelist, mpi_type);
        MPI_Type_commit(mpi_type);
    }


任何帮助都将不胜感激。
编辑:有助于解决问题,而不是稍微有用的StackOverflow术语

最佳答案

这部分是错误的:

int blocklengths[6] = {1,1, NUM_CITIES, NUM_CITIES, 1, 1};
MPI_Datatype    types[6] = {MPI_INT, MPI_INT, MPI_TABU, MPI_PATH, MPI_INT, MPI_DOUBLE};
MPI_Aint        offsets[6] = { offsetof( ACO_Ant, city ), offsetof( ACO_Ant, next_city), offsetof( ACO_Ant, tabu), offsetof( ACO_Ant, path ), offsetof( ACO_Ant, path_index ), offsetof( ACO_Ant, tour_distance )};

MPI_TABUMPI_PATH数据类型已经覆盖了NUM_CITIES元素。当您将相应的块大小指定为NUM_CITIES时,生成的数据类型将尝试访问NUM_CITIES * NUM_CITIES元素,这可能会导致segfault(信号11)。
blocklengths的所有元素设置为1或用MPI_TABU替换MPI_PATH数组中的typesMPI_INT
这一部分也错了:
MPI_Type_create_struct(6, blocklengths, offsets, types, &tmp_type);
MPI_Type_get_extent( tmp_type, &lb, &extent );
//Tried all of these
MPI_Type_create_resized( tmp_type, lb, extent, &MPI_ANT );
//MPI_Type_create_resized( tmp_type, 0, sizeof(MPI_ANT), &MPI_ANT );
//MPI_Type_create_resized( tmp_type, 0, sizeof(ant), &MPI_ANT );
MPI_Type_commit(&MPI_ANT);

MPI_Type_create_resized返回的值调用MPI_Type_get_extent是没有意义的,因为它只是复制类型而没有实际调整它的大小。使用sizeof(MPI_ANT)是错误的,因为MPI_ANT不是C类型,而是MPI句柄,它是整数索引或指针(依赖于实现)。如果sizeof(ant)ant类型,但给定您调用ACO_Ant,则MPI_Bcast(ant, NUM_ANTS, ...)可以是指针,在这种情况下ant只是指针大小,或者它是数组,在这种情况下sizeof(ant)比它必须大一倍。正确的做法是:
MPI_Type_create_resized(tmp_type, 0, sizeof(ACO_Ant), &ant_type);
MPI_Type_commit(&ant_type);

请不要在自己的变量或函数名中使用sizeof(ant)作为前缀。这使得代码不可读,并且具有误导性(“这是预定义的MPI数据类型还是用户定义的数据类型?”)
至于最后一个问题,作者可能有一个不同的结构。只要使用正确数量的有效元素调用NUM_ANTS,就不会停止使用较大的数组。
注意:您不必提交从未在通信调用中直接使用的MPI数据类型。也就是说,这两行是不必要的:
MPI_Type_commit(&MPI_TABU);
MPI_Type_commit(&MPI_PATH);

关于c - 创建MPI结构时出现问题,调用MPI_Bcast时出现错误11,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/55678073/

10-11 23:01
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