From 809decbc563eab07f05f0fbe478683390f514daa Mon Sep 17 00:00:00 2001
From: Patrick Mullen <pdmullen@pn2293621.lanl.gov>
Date: Mon, 13 Nov 2023 15:28:24 -0700
Subject: [PATCH] Construct integrators via string name

---
 src/time_integration/butcher_integrator.cpp   | 19 +++++++++++++++++--
 .../low_storage_integrator.cpp                | 16 ++++++++++++++--
 src/time_integration/staged_integrator.hpp    |  2 ++
 3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/time_integration/butcher_integrator.cpp b/src/time_integration/butcher_integrator.cpp
index d90de479ec68..40096dd1eeba 100644
--- a/src/time_integration/butcher_integrator.cpp
+++ b/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) {
diff --git a/src/time_integration/low_storage_integrator.cpp b/src/time_integration/low_storage_integrator.cpp
index ab874d98e050..d833ddd8ad20 100644
--- a/src/time_integration/low_storage_integrator.cpp
+++ b/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
diff --git a/src/time_integration/staged_integrator.hpp b/src/time_integration/staged_integrator.hpp
index 0d22d7d85600..329f69bc294b 100644
--- a/src/time_integration/staged_integrator.hpp
+++ b/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;