Construct staged integrators via arbitrary name

CHANGELOG.md

@@ -21,6 +21,7 @@
 - [[PR 868]](https://github.com/parthenon-hpc-lab/parthenon/pull/868) Add block-local face, edge, and nodal fields and allow for packing
 
 ### Changed (changing behavior/API/variables/...)
+- [[PR 975]](https://github.com/parthenon-hpc-lab/parthenon/pull/975) Construct staged integrators via arbitrary name
 - [[PR 976]](https://github.com/parthenon-hpc-lab/parthenon/pull/976) Move UserWorkBeforeLoop to be after first output
 - [[PR 965]](https://github.com/parthenon-hpc-lab/parthenon/pull/965) Allow leading whitespace in input parameters
 - [[PR 926]](https://github.com/parthenon-hpc-lab/parthenon/pull/926) Internal refinement op registration

src/time_integration/butcher_integrator.cpp

@@ -36,8 +36,12 @@ namespace parthenon {
  * alpha_k = c_k
  * c_k = b_k
  */
-ButcherIntegrator::ButcherIntegrator(ParameterInput *pin)
-    : StagedIntegrator(pin->GetOrAddString("parthenon/time", "integrator", "rk2")) {
+
+//----------------------------------------------------------------------------------------
+//! \class ButcherIntegrator::ButcherIntegrator(const std::string &name)
+//! \brief Constructs a ButcherIntegrator instance given a string (e.g., rk2, rk3..)
+
+ButcherIntegrator::ButcherIntegrator(const std::string &name) : StagedIntegrator(name) {
   if (name_ == "rk1") {
     nstages = nbuffers = 1;
     Resize_(nstages);
@@ -219,6 +223,17 @@ ButcherIntegrator::ButcherIntegrator(ParameterInput *pin)
   }
 }
 
+//----------------------------------------------------------------------------------------
+//! \class ButcherIntegrator::ButcherIntegrator(ParameterInput *pin)
+//! \brief Constructs a ButcherIntegrator instance given ParameterInput *pin
+
+ButcherIntegrator::ButcherIntegrator(ParameterInput *pin)
+    : ButcherIntegrator(pin->GetOrAddString("parthenon/time", "integrator", "rk2")) {}
+
+//----------------------------------------------------------------------------------------
+//! \fn  void ButcherIntegrator::Resize_(int nstages)
+//! \brief Resizes ButcherIntegrator registers given a supplied integer nstages
+
 void ButcherIntegrator::Resize_(int nstages) {
   a.resize(nstages);
   for (int i = 0; i < a.size(); ++i) {

src/time_integration/low_storage_integrator.cpp

@@ -43,8 +43,13 @@ namespace parthenon {
  * Stone et al., ApJS (2020) 249:4
  * See equations 11 through 15.
  */
-LowStorageIntegrator::LowStorageIntegrator(ParameterInput *pin)
-    : StagedIntegrator(pin->GetOrAddString("parthenon/time", "integrator", "rk2")) {
+
+//----------------------------------------------------------------------------------------
+//! \class LowStorageIntegrator::LowStorageIntegrator(const std::string &name)
+//! \brief Constructs a LowStorageIntegrator instance given a string (e.g., rk2, rk3..)
+
+LowStorageIntegrator::LowStorageIntegrator(const std::string &name)
+    : StagedIntegrator(name) {
   if (name_ == "rk1") {
     nstages = 1;
     nbuffers = 1;
@@ -155,4 +160,11 @@ LowStorageIntegrator::LowStorageIntegrator(ParameterInput *pin)
   MakePeriodicNames_(stage_name, nstages);
 }
 
+//----------------------------------------------------------------------------------------
+//! \class LowStorageIntegrator::LowStorageIntegrator(ParameterInput *pin)
+//! \brief Constructs a LowStorageIntegrator instance given ParameterInput *pin
+
+LowStorageIntegrator::LowStorageIntegrator(ParameterInput *pin)
+    : LowStorageIntegrator(pin->GetOrAddString("parthenon/time", "integrator", "rk2")) {}
+
 } // namespace parthenon

src/time_integration/staged_integrator.hpp

@@ -49,6 +49,7 @@ class StagedIntegrator {
 class LowStorageIntegrator : public StagedIntegrator {
  public:
   LowStorageIntegrator() = default;
+  explicit LowStorageIntegrator(const std::string &name);
   explicit LowStorageIntegrator(ParameterInput *pin);
   std::vector<Real> delta;
   std::vector<Real> beta;
@@ -60,6 +61,7 @@ class LowStorageIntegrator : public StagedIntegrator {
 class ButcherIntegrator : public StagedIntegrator {
  public:
   ButcherIntegrator() = default;
+  explicit ButcherIntegrator(const std::string &name);
   explicit ButcherIntegrator(ParameterInput *pin);
   // TODO(JMM): Should I do a flat array with indexing instead?
   std::vector<std::vector<Real>> a;