else if (to_right == -1) {
Request::recv(buf, count, datatype, from, tag, comm, &status);
Request::send(buf, count, datatype, to_left, tag, comm);
}
else if (to_right == -1) {
Request::recv(buf, count, datatype, from, tag, comm, &status);
Request::send(buf, count, datatype, to_left, tag, comm);
}