Question

我遇到以下问题，我正在尝试发送2种类型的数据，1个int和2个char，这是我程序的一部分

#define Send(send_data, count, type, dest, tag) MPI_Send(send_data, count, type, dest, tag, GROUP)
#define Recv(recv_data, count, type, source, tag) MPI_Recv(recv_data, count, type, source, tag, GROUP, &status)
#define Recv(recv_data, count, type, source, tag) MPI_Recv(recv_data, count, type, source, tag, GROUP, &status)
#define Pack(data_in, count_in, type, data_out, count_out, pos) MPI_Pack(data_in, count_in, type, data_out, count_out, pos, GROUP)
#define Unpack(data_out, count_out, pos, data_in, count_in, type) MPI_Unpack(data_out, count_out, pos, data_in, count_in, type, GROUP)
#define Pack_size(count, type, size) MPI_Pack_size(count, type, GROUP, size)
#define MASTER 0


if( rank == 0 ){

    k1 = strlen(prog);
    k2 = strlen(gamesspath);

    for( i = 1; i < proc; i++ ){
      Send(&k1, 1, INT, i, 1);
      Send(&k2, 1, INT, i, 2);
    }
  }
  else{
    Recv(&k1, 1, INT, MASTER, 1);
    Recv(&k2, 1, INT, MASTER, 2);

    gamesspath = malloc( k2 * sizeof(char));
  }

  Pack_size(k1, CHAR, &size1);
  Pack_size(k2, CHAR, &size2);
  Pack_size(1, INT, &size3);

  buffer_size = size1 + size2 + size3;

  buffer = malloc( buffer_size * sizeof(char));

  if( rank == MASTER ){
    pos = 0;

    Pack(prog, k1, CHAR, buffer, buffer_size, &pos);
    Pack(gamesspath, k2, CHAR, buffer, buffer_size, &pos);
    Pack(&nindiv, 1, INT, buffer, buffer_size, &pos);
  }

  Bcast(buffer, buffer_size, PACKED);

  if( rank != MASTER ){
    pos = 0;

    Unpack(buffer, buffer_size, &pos, prog, k1, CHAR);
    Unpack(buffer, buffer_size, &pos, gamesspath, k2, CHAR);
    Unpack(buffer, buffer_size, &pos, &nindiv, 1, INT);
  }

  /*FIM DO ENVIO*/

  printf("PROG = %s, GAMESSPATH = %s, NINDIV = %d - rank %d\n", prog, gamesspath, nindiv, rank);

但我得到以下结果

PROG = GAMESS, GAMESSPATH = /usr/local/gamess/rungms1, NINDIV = 10 - rank 1
PROG = GAMESS, GAMESSPATH = /usr/local/gamess/rungms, NINDIV = 10 - rank 0

我的问题在于排名1的GAMESSPATH，/ usr / local / gamess / rungms1 等级0，/ usr / local / gamess / rungms

你可以注意到在等级1的GAMESS PATH结尾处，出现数字1，但我无法找到错误。

Answer 1

C中的字符串以空字节终止。 strlen返回不带空字节的字符串长度。因此，当您使用MPI发送字符串时，而不是接收器处的终止空字节，最后会有一些垃圾数据。

一个简单的解决方法是将strlen返回的值加1。如果长度值可能溢出，这确实有安全隐患。这可能不是科学代码中的问题，而是需要注意的事项。

另外，为什么需要打包缓冲区？看起来这些字符串在连续存储中。您也不需要发送长度：只需告诉接收方接收最大缓冲区大小，并使用发送方的实际长度。

MPI_Bcast发送字符串

1 个答案: