MSG_task_send(MSG_task_create(allreduce_identifier, 0, comm_size, NULL),
mailbox);
sprintf(mailbox, "%s_p0_%s", allreduce_identifier, process_name);
MSG_task_receive(&task, mailbox);
MSG_task_destroy(task);
MSG_task_send(MSG_task_create(allreduce_identifier, 0, comm_size, NULL),
mailbox);
sprintf(mailbox, "%s_p0_%s", allreduce_identifier, process_name);
MSG_task_receive(&task, mailbox);
MSG_task_destroy(task);