tweak load balancing output format

                                   MPI_Wtime()-start_time);

    mesg += fmt::format("  iteration count = {}\n",niter);

    for (int i = 0; i < nimbalance; ++i) mesg += imbalances[i]->info();

    mesg += fmt::format("  initial/final maximal load/proc = {} {}\n"

                        "  initial/final imbalance factor  = {:.6g} {:.6g}\n",

    mesg += fmt::format("  initial/final maximal load/proc = {:.8} {:.8}\n"

                        "  initial/final imbalance factor  = {:.8} {:.8}\n",

                        maxinit,maxfinal,imbinit,imbfinal);

    if (style != BISECTION) {

      mesg += "  x cuts:";

      for (int i = 0; i <= comm->procgrid[0]; i++)

        mesg += fmt::format(" {}",comm->xsplit[i]);

        mesg += fmt::format(" {:.8}",comm->xsplit[i]);

      mesg += "\n  y cuts:";

      for (int i = 0; i <= comm->procgrid[1]; i++)

        mesg += fmt::format(" {}",comm->ysplit[i]);

        mesg += fmt::format(" {:.8}",comm->ysplit[i]);

      mesg += "\n  z cuts:";

      for (int i = 0; i <= comm->procgrid[2]; i++)

        mesg += fmt::format(" {}",comm->zsplit[i]);

        mesg += fmt::format(" {:.8}",comm->zsplit[i]);

      mesg += "\n";

    }