[mpfa][elemfluxvarcache] do not sort indices, use find instead

Originally it was thought that the list of scvf indices might not be unique,
which is why we sorted and made the entries unique. This is not the case though.

dumux/discretization/cellcentered/mpfa/elementfluxvariablescache.hh

@@ -18,7 +18,7 @@
  *****************************************************************************/
 /*!
  * \file
- * \brief The global object of flux var caches
+ * \brief The local object of flux var caches
  */
 #ifndef DUMUX_DISCRETIZATION_CCMPFA_ELEMENT_FLUXVARSCACHE_HH
 #define DUMUX_DISCRETIZATION_CCMPFA_ELEMENT_FLUXVARSCACHE_HH
@@ -32,7 +32,8 @@ namespace Dumux
 
 /*!
  * \ingroup ImplicitModel
- * \brief Base class for the stencil local flux variables cache
+ * \brief Base class for the local flux variables cache.
+ *        Prepares the cache on all the faces in the stencil.
  */
 template<class TypeTag, bool EnableGlobalFluxVariablesCache>
 class CCMpfaElementFluxVariablesCache;
@@ -135,7 +136,8 @@ public:
               const FVElementGeometry& fvGeometry,
               const ElementVolumeVariables& elemVolVars)
     {
-        clear();
+        fluxVarsCache_.clear();
+        globalScvfIndices_.clear();
 
         const auto& problem = globalFluxVarsCache().problem_();
         const auto& globalFvGeometry = problem.model().globalFvGeometry();
@@ -143,8 +145,10 @@ public:
         const auto& assemblyMap = problem.model().localJacobian().assemblyMap();
         const auto globalI = problem.elementMapper().index(element);
 
-        // reserve initial guess of memory (won't be enough though - several scvfs per neighbor will be required)
-        globalScvfIndices_.reserve(fvGeometry.numScvf() + assemblyMap[globalI].size());
+        // reserve memory
+        auto numNeighborScvfs = 0;
+        for (auto&& facesInNeighbor : assemblyMap[globalI]) numNeighborScvfs += facesInNeighbor.size();
+        globalScvfIndices_.reserve(fvGeometry.numScvf() + numNeighborScvfs);
 
         // first add all the indices inside the element
         for (auto&& scvf : scvfs(fvGeometry))
@@ -155,17 +159,11 @@ public:
             for (auto fluxVarIdx : assemblyMap[globalI][j])
                 globalScvfIndices_.push_back(fluxVarIdx);
 
-        // make global indices unique
-        std::sort(globalScvfIndices_.begin(), globalScvfIndices_.end());
-        globalScvfIndices_.erase(std::unique(globalScvfIndices_.begin(), globalScvfIndices_.end()), globalScvfIndices_.end());
-
         // prepare all the caches of the scvfs inside the corresponding interaction volumes using helper class
         fluxVarsCache_.resize(globalScvfIndices_.size());
         for (auto&& scvf : scvfs(fvGeometry))
-        {
             if (!(*this)[scvf].isUpdated())
                 FluxVariablesCacheFiller::fillFluxVarCache(problem, element, fvGeometry, elemVolVars, scvf, *this);
-        }
 
         // prepare the caches in the remaining neighbors
         unsigned int j = 0;
@@ -215,12 +213,6 @@ public:
 private:
     const GlobalFluxVariablesCache* globalFluxVarsCachePtr_;
 
-    void clear()
-    {
-        fluxVarsCache_.clear();
-        globalScvfIndices_.clear();
-    }
-
     // This function updates the transmissibilities after the solution has been deflected during jacobian assembly
     void update(const Element& element,
                 const FVElementGeometry& fvGeometry,
@@ -230,16 +222,14 @@ private:
             (*this)[scvf].setUpdateStatus(false);
 
         for (auto&& scvf : scvfs(fvGeometry))
-        {
             if (!(*this)[scvf].isUpdated())
                 FluxVariablesCacheFiller::updateFluxVarCache(globalFluxVarsCache().problem_(), element, fvGeometry, elemVolVars, scvf, *this);
-        }
     }
 
-    // get index of scvf in the local container
+    // get index of an scvf in the local container
     int getLocalScvfIdx_(const int scvfIdx) const
     {
-        auto it = std::lower_bound(globalScvfIndices_.begin(), globalScvfIndices_.end(), scvfIdx);
+        auto it = std::find(globalScvfIndices_.begin(), globalScvfIndices_.end(), scvfIdx);
         assert(globalScvfIndices_[std::distance(globalScvfIndices_.begin(), it)] == scvfIdx && "Could not find the flux vars cache for scvfIdx");
         return std::distance(globalScvfIndices_.begin(), it);
     }