Parthenon Manager

The ParthenonManager class helps set up a parthenon-based application. An instance of ParthenonManager owns pointers a number of sub-objects:

• The ApplicationInput struct, which lets users set things like the ProcessPackages and ProblemGenerator function pointers.

• The ParameterInput class, which populates input parameters from the input file and command line

• The Mesh object

The ParthenonManager has two important methods that usually must be called in the main function of a parthenon-based app. The function

ParthenonStatus ParthenonManager::ParthenonInitEnv(int argc, char *argv);

reads the input deck and populates the ParameterInput object pointer pman.pin, and sets up the MPI, and Kokkos runtimes. The function

void ParthenonManager::ParthenonInitPackagesAndMesh();

Calls the Initialize(ParameterInput *pin) function of all packages to be utilized and creates the grid hierarchy, including the Mesh and MeshBlock objects, and calls the ProblemGenerator (and PostInitialization) routines.

The reason these functions are split out is to enable decisions to be made by the application between reading the input deck and setting up the grid. For example, during problem initialization, ProblemGenerator may be used to be the user-facing API to describe initial conditions, whereas, PostInitialization could use those user-specified fields to sync all fields prior to entering communication routines. A common use-case is:

using parthenon::ParthenonManager;
using parthenon::ParthenonStatus;
ParthenonManager pman;

// call ParthenonInit to initialize MPI and Kokkos, parse the input deck, and set up
auto manager_status = pman.ParthenonInitEnv(argc, argv);
if (manager_status == ParthenonStatus::complete) {
  pman.ParthenonFinalize();
  return 0;
}
if (manager_status == ParthenonStatus::error) {
  pman.ParthenonFinalize();
  return 1;
}

// Redefine parthenon defaults
pman.app_input->ProcessPackages = MyProcessPackages;
std::string prob = pman.pin->GetString("app", "problem");
if (prob == "problem1") {
  pman.app_input->ProblemGenerator = Problem1Generator;
  pman.app_input->PostInitialization = Problem1PostInitialization;
} else {
  pman.app_input->ProblemGenerator = Problem2Generator;
}

pman.ParthenonInitPackagesAndMesh();