Alltoall
Alltoall is a collective communication operation used in parallel computing, in which every process starts with a block of data for each process in the communicator and ends with a block of data for every process. Specifically, each process sends a distinct data block to every other process and receives a distinct data block from every other process. After the operation, each process has a concatenation of the blocks received from all processes, resulting in data that has been redistributed across the processes.
In the Message Passing Interface (MPI), the standard alltoall operation is MPI_Alltoall. When all processes participate,
Common use cases include matrix transposition, data redistribution after a decomposition, or shuffling data for parallel
Performance depends on the network and implementation; the total data exchanged is proportional to p*(p-1) blocks,