simgrid::smpi::Topo_Cart* topo = new simgrid::smpi::Topo_Cart(comm_old, ndims, dims, periodic, reorder, comm_cart);
if (*comm_cart == MPI_COMM_NULL) {
delete topo;
simgrid::smpi::Topo_Cart* topo = new simgrid::smpi::Topo_Cart(comm_old, ndims, dims, periodic, reorder, comm_cart);
if (*comm_cart == MPI_COMM_NULL) {
delete topo;