rank 0
send_list = 0a | 0b | 0c | 0d
receive_buf = __ | __ | __ | __
all_to_all(send_list, recieve_buf)
receive_buf: 0a | 1a | 2a | 3a
rank 1
send_list = 1a | 1b | 1c | 1d
receive_buf = __ | __ | __ | __
all_to_all(send_list, recieve_buf)
receive_buf: 0b | 1b | 2b | 3b
rank 2
send_list = 2a | 2b | 2c | 2d
receive_buf = __ | __ | __ | __
all_to_all(send_list, recieve_buf)
receive_buf: 0c | 1c | 2c | 3c
rank 3
send_list = 3a | 3b | 3c | 3d
receive_buf = __ | __ | __ | __
all_to_all(send_list, recieve_buf)
receive_buf: 0d | 1d | 2d | 3d