// Copyright 2021 Jeisson Hidalgo CC-BY 4.0 #include #include #include #include #include #define fail(msg) throw std::runtime_error(msg) void simulate_relay_race(int argc, char* argv[], int process_number , int process_count); void run_stage1(int stage1_delay, int process_number, int team_count); void run_stage2(int stage2_delay, int process_number, int team_count); void referee(int team_count); int main(int argc, char* argv[]) { int error = EXIT_SUCCESS; if (MPI_Init(&argc, &argv) == MPI_SUCCESS) { try { int process_number = -1; MPI_Comm_rank(MPI_COMM_WORLD, &process_number); int process_count = -1; MPI_Comm_size(MPI_COMM_WORLD, &process_count); char process_hostname[MPI_MAX_PROCESSOR_NAME] = { '\0' }; int hostname_length = -1; MPI_Get_processor_name(process_hostname, &hostname_length); simulate_relay_race(argc, argv, process_number, process_count); } catch (const std::runtime_error& exception) { std::cout << exception.what() << std::endl; error = EXIT_FAILURE; } MPI_Finalize(); } else { std::cerr << "error: could not init MPI" << std::endl; error = EXIT_FAILURE; } return error; } void simulate_relay_race(int argc, char* argv[], int process_number , int process_count) { if (argc == 3) { if (process_count >= 3 && process_count % 2 == 1) { const int team_count = (process_count - 1) / 2; const int stage1_delay = atoi(argv[1]); const int stage2_delay = atoi(argv[2]); if (process_number == 0) { referee(team_count); } else if (process_number <= team_count) { run_stage1(stage1_delay, process_number, team_count); } else { run_stage2(stage2_delay, process_number, team_count); } } else { fail("error: process count must be odd and greater than 3"); } } else { fail("usage: relay_race_dist stage1_delay stage2_delay"); } } void run_stage1(int stage1_delay, int process_number, int team_count) { // wait_barrier() if (MPI_Barrier(MPI_COMM_WORLD) != MPI_SUCCESS) { fail("error: could wait for barrier"); } usleep(1000 * stage1_delay); const int peer = process_number + team_count; bool baton = true; // send(&baton, 1, peer) if (MPI_Send(&baton, /*count*/ 1, MPI_C_BOOL, peer, /*tag*/ 0 , MPI_COMM_WORLD) != MPI_SUCCESS) { fail("error: could not send baton"); } } void run_stage2(int stage2_delay, int process_number, int team_count) { // wait_barrier() if (MPI_Barrier(MPI_COMM_WORLD) != MPI_SUCCESS) { fail("error: could wait for barrier"); } int peer = process_number - team_count; bool baton = false; // receive(&baton, 1, peer) if (MPI_Recv(&baton, /*capacity*/ 1, MPI_C_BOOL, /*source*/ peer , /*tag*/ 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE) != MPI_SUCCESS ) { fail("could not receive baton"); } usleep(1000 * stage2_delay); // send(&peer, 1, 0) if (MPI_Send(&peer, /*count*/ 1, MPI_INT, /*target*/ 0, /*tag*/ 0 , MPI_COMM_WORLD) != MPI_SUCCESS) { fail("error: could not send team number to referee"); } } void referee(int team_count) { const double start_time = MPI_Wtime(); // wait_barrier() if (MPI_Barrier(MPI_COMM_WORLD) != MPI_SUCCESS) { fail("error: could wait for barrier"); } int place = 0; for (int index = 0; index < team_count; ++index) { int team = 0; // receive(&team, 1, any_process) if (MPI_Recv(&team, /*capacity*/ 1, MPI_INT, MPI_ANY_SOURCE , /*tag*/ 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE) != MPI_SUCCESS ) { fail("error: could not receive team number"); } const double elapsed = MPI_Wtime() - start_time; ++place; std::cout << "Place " << place << ": team " << team << " in " << elapsed << "s" << std::endl; } }