Dear all, I was testing your example in example/parapack/exchange with the exchange.ip modified to only test the ising case, however with more sweeps, to test the time spent. I know that the parallel_exchange_worker gets called (visible via the line "EXMC: number of replicas on each process = 2 2", which will only be outputted by the parallel_exchange_worker). I would by this output assume that different replicas get distributed over the cores,. The time spent in the simulation however stays the same irrespective of the number of processes I provide to MPI or not even call the MPI library at all. I call the function in the following way: mpirun -np 2 ./exchange --mpi < exchange.ip resp. ./exchange < exchange.ip Do I miss an important argument in the input file / command line argument, that prevents the parallel execution of replicas? Best, Dominik -- Paul Scherrer Institut Dominik Schildknecht PhD Student WHGA/129 CH-5232 Villigen-PSI Phone: +41 56 310 55 68