From 19f4cef6c1eaff81edc576ef3f80cba622ece4e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Atgeirr=20Fl=C3=B8=20Rasmussen?= <atgeirr@sintef.no>
Date: Fri, 15 Jan 2016 15:16:40 +0100
Subject: [PATCH] Add new step() overload taking initial states separately.

---
 opm/autodiff/NonlinearSolver.hpp      | 25 +++++++++++++++++++++----
 opm/autodiff/NonlinearSolver_impl.hpp | 16 +++++++++++++++-
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/opm/autodiff/NonlinearSolver.hpp b/opm/autodiff/NonlinearSolver.hpp
index 641cb2fd0..d67ee6122 100644
--- a/opm/autodiff/NonlinearSolver.hpp
+++ b/opm/autodiff/NonlinearSolver.hpp
@@ -76,15 +76,32 @@ namespace Opm {
 
         /// Take a single forward step, after which the states will be modified
         /// according to the physical model.
-        /// \param[in] dt                time step size
-        /// \param[in] reservoir_state   reservoir state variables
-        /// \param[in] well_state        well state variables
-        /// \return                      number of linear iterations used
+        /// \param[in] dt                       time step size
+        /// \param[in, out] reservoir_state     reservoir state variables
+        /// \param[in, out] well_state          well state variables
+        /// \return                             number of linear iterations used
         int
         step(const double dt,
              ReservoirState& reservoir_state,
              WellState& well_state);
 
+        /// Take a single forward step, after which the states will be modified
+        /// according to the physical model. This version allows for the
+        /// states passed as in/out arguments to be different from the initial
+        /// states.
+        /// \param[in] dt                       time step size
+        /// \param[in] initial_reservoir_state  reservoir state variables at start of timestep
+        /// \param[in] initial_well_state       well state variables at start of timestep
+        /// \param[in, out] reservoir_state     reservoir state variables
+        /// \param[in, out] well_state          well state variables
+        /// \return                             number of linear iterations used
+        int
+        step(const double dt,
+             const ReservoirState& initial_reservoir_state,
+             const WellState& initial_well_state,
+             ReservoirState& reservoir_state,
+             WellState& well_state);
+
         /// Number of nonlinear solver iterations used in all calls to step().
         unsigned int nonlinearIterations() const;
 
diff --git a/opm/autodiff/NonlinearSolver_impl.hpp b/opm/autodiff/NonlinearSolver_impl.hpp
index d35d1fa8f..9b52235e5 100644
--- a/opm/autodiff/NonlinearSolver_impl.hpp
+++ b/opm/autodiff/NonlinearSolver_impl.hpp
@@ -85,9 +85,23 @@ namespace Opm
     step(const double dt,
          ReservoirState& reservoir_state,
          WellState& well_state)
+    {
+        return step(dt, reservoir_state, well_state, reservoir_state, well_state);
+    }
+
+
+
+    template <class PhysicalModel>
+    int
+    NonlinearSolver<PhysicalModel>::
+    step(const double dt,
+         const ReservoirState& initial_reservoir_state,
+         const WellState& initial_well_state,
+         ReservoirState& reservoir_state,
+         WellState& well_state)
     {
         // Do model-specific once-per-step calculations.
-        model_->prepareStep(dt, reservoir_state, well_state);
+        model_->prepareStep(dt, initial_reservoir_state, initial_well_state);
 
         int iteration = 0;