我有一个一维矩阵数据。在每次迭代中，每个处理器更新其Q_send_matrix并将其发送到上一个处理器（Q_send_matrix），而它从下一个处理器（rank-1）接收新更新的矩阵作为Q_recv_matrix。例如，在迭代中，rank+1更新其Proc[0]并将其发送到Q_send_matrix，而它从Proc[3]接收Q_recv_matrix。正如你所估计的，这就像一个环形通信。请看下面的代码后，我的解释下面的代码。
MPI_Request request;
MPI_Status status;
// All the elements of Q_send and Q_recv buffers
// are set to 1.0 initially. Each processor
// updates its Q_send buffer to prepare it
// to be sent below.(above part is big, so it
// is not added here...)
/**
* Transfer Q matrix blocks among processors
* + Each processor sends the Q matrix
* + to the previous processor while receives
* + the Q matrix from the next processor
* + It is like a ring communication
* */
/* Receive Q matrix with MPI_Irecv */
source = (my_rank+1)%comm_size;
recv_count = no_col_per_proc[source]*input_k;
MPI_Irecv(Q_recv_matrix, recv_count,
MPI_FP_TYPE, source,
0, MPI_COMM_WORLD,
&request);
/* Send Q matrix */
dest = (my_rank-1+comm_size)%comm_size;
send_count = no_col_per_proc[my_rank]*input_k;
MPI_Send(Q_send_matrix, send_count,
MPI_FP_TYPE, dest,
0, MPI_COMM_WORLD);
/* Wait status */
// MPI_Wait(request, status);
/* Barrier */
MPI_Barrier(MPI_COMM_WORLD);
/* Print Q send and receive matrices */
for( j = 0; j < send_count; j ++ )
{
printf("P[%d] sends Q_send[%d] to P[%d] = %.2f\n",
my_rank, j, dest, Q_send_matrix[j]);
}
for( j = 0; j < recv_count; j ++ )
{
printf("P[%d] receives Q_recv[%d] from P[%d] = %.2f\n",
my_rank, j, source, Q_recv_matrix[j]);
}
我想用同步音来进行交流。但是，由于基于其阻塞特性的死锁，
Proc[1]和MPI_Send不可能。因此，我将MPI_Recv和MPI_Irecv与MPI_Send一起使用。但是，它没有完成，所有的处理器都在等待。所以，我用MPI_Wait代替MPI_Barrier使它们同步，并解决了处理器的等待问题，因此它们完成了工作。但是，它没有正常工作。以下代码的某些输出是错误的。每个处理器发送正确的数据，发送端没有问题。另一方面，接收的数据缓冲区没有变化。这意味着，在某些处理器中，即使从如下所述的其他处理器之一接收到数据，所接收缓冲区的初始值仍然保持不变。P[0] sends Q_send[0] to P[3] = -2.12
P[0] sends Q_send[1] to P[3] = -2.12
P[0] sends Q_send[2] to P[3] = 4.12
P[0] sends Q_send[3] to P[3] = 4.12
P[0] receives Q_recv[0] from P[1] = 1.00
P[0] receives Q_recv[1] from P[1] = 1.00
P[0] receives Q_recv[2] from P[1] = 1.00
P[0] receives Q_recv[3] from P[1] = 1.00
P[1] sends Q_send[0] to P[0] = -2.12
P[1] sends Q_send[1] to P[0] = -2.12
P[1] sends Q_send[2] to P[0] = 0.38
P[1] sends Q_send[3] to P[0] = 0.38
P[1] receives Q_recv[0] from P[2] = 1.00
P[1] receives Q_recv[1] from P[2] = 1.00
P[1] receives Q_recv[2] from P[2] = 1.00
P[1] receives Q_recv[3] from P[2] = 1.00
P[2] sends Q_send[0] to P[1] = 1.00
P[2] sends Q_send[1] to P[1] = 1.00
P[2] sends Q_send[2] to P[1] = -24.03
P[2] sends Q_send[3] to P[1] = -24.03
P[2] receives Q_recv[0] from P[3] = 1.00
P[2] receives Q_recv[1] from P[3] = 1.00
P[2] receives Q_recv[2] from P[3] = 1.00
P[2] receives Q_recv[3] from P[3] = 1.00
P[3] sends Q_send[0] to P[2] = 7.95
P[3] sends Q_send[1] to P[2] = 7.95
P[3] sends Q_send[2] to P[2] = 0.38
P[3] sends Q_send[3] to P[2] = 0.38
P[3] receives Q_recv[0] from P[0] = -2.12
P[3] receives Q_recv[1] from P[0] = -2.12
P[3] receives Q_recv[2] from P[0] = 4.12
P[3] receives Q_recv[3] from P[0] = 4.12
最佳答案
在访问MPI_Wait中的数据之前，必须完成MPI_Test或成功的MPI_Irecv。你不能用屏障代替它。
对于环形通信，请考虑使用MPI_Sendrecv。它可以比使用异步通信更简单。
关于c - MPI_Irecv无法正确接收MPI_Send发送的数据，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/42121393/