attempt to remove excessive allocations in updater (#736)

updater less allocations

src/amr/multiphysics_integrator.hpp

@@ -335,6 +335,7 @@ namespace solver
                 {
                     messenger.registerLevel(hierarchy, ilvl);
                 }
+                solver.onRegrid();
             }
             else
             {

src/amr/solvers/solver.hpp

@@ -85,6 +85,8 @@ namespace solver
 
 
 
+        virtual void onRegrid() {} // do what you need to do on regrid
+
 
         virtual ~ISolver() = default;
 

src/amr/solvers/solver_ppc.hpp

@@ -94,6 +94,7 @@ class SolverPPC : public ISolver<AMR_Types>
                               double const currentTime, double const newTime) override;
 
 
+    void onRegrid() override { ionUpdater_.reset(); }
 
 private:
     using Messenger = amr::HybridMessenger<HybridModel>;

src/core/data/particles/particle_array.hpp

@@ -173,7 +173,7 @@ class ParticleArray
     }
 
     template<typename Predicate>
-    void export_particles(This& dest, Predicate&& pred) const
+    void export_particles(ParticleArray& dest, Predicate&& pred) const
     {
         PHARE_LOG_SCOPE("ParticleArray::export_particles (Fn,vector)");
         cellMap_.export_if(particles_.data(), dest, std::forward<Predicate>(pred));
@@ -233,6 +233,19 @@ class ParticleArray
 
     auto& box() const { return box_; }
 
+
+    auto& replace_from(ParticleArray const& that)
+    {
+        if (this == &that) // just in case
+            return *this;
+        this->resize(that.size());
+        std::copy(that.begin(), that.end(), this->begin());
+        this->box_     = that.box_;
+        this->cellMap_ = that.cellMap_;
+        return *this;
+    }
+
+
 private:
     Vector particles_;
     box_t box_;

src/core/numerics/ion_updater/ion_updater.hpp

@@ -62,10 +62,21 @@ class IonUpdater
     void updateIons(Ions& ions, GridLayout const& layout);
 
 
+    void reset()
+    {
+        // clear memory
+        tmp_particles_ = std::move(ParticleArray{Box{}});
+    }
+
+
 private:
     void updateAndDepositDomain_(Ions& ions, Electromag const& em, GridLayout const& layout);
 
     void updateAndDepositAll_(Ions& ions, Electromag const& em, GridLayout const& layout);
+
+
+    // dealloced on regridding/load balancing coarsest
+    ParticleArray tmp_particles_{Box{}}; //{std::make_unique<ParticleArray>(Box{})};
 };
 
 
@@ -162,8 +173,7 @@ void IonUpdater<Ions, Electromag, GridLayout>::updateAndDepositDomain_(Ions& ion
         // deposit moments on those which leave to go inDomainBox
 
         auto pushAndAccumulateGhosts = [&](auto& inputArray, bool copyInDomain = false) {
-            auto outputArray{inputArray}; // TODO : dynamic allocation can we get rid of that
-            //      eventually?
+            auto& outputArray = tmp_particles_.replace_from(inputArray);
 
             inRange  = makeIndexRange(inputArray);
             outRange = makeIndexRange(outputArray);

src/core/utilities/types.hpp

@@ -236,10 +236,7 @@ namespace core
             return std::string{val};
         return std::nullopt;
     }
-    NO_DISCARD inline std::optional<std::string> get_env(std::string&& key)
-    {
-        return get_env(key);
-    }
+
 
 } // namespace core
 } // namespace PHARE
@@ -339,6 +336,7 @@ NO_DISCARD auto any(Container const& container, Fn fn = to_bool)
     return std::any_of(container.begin(), container.end(), fn);
 }
 
+
 template<typename Container, typename Fn = decltype(to_bool)>
 NO_DISCARD auto none(Container const& container, Fn fn = to_bool)
 {