Merge branch 'feature/fix-assemblebulk' into 'master'

[bugfix] Zero-initialize matrix before assembling entries

See merge request !100

dune/fufem/assemblers/dunefunctionsoperatorassembler.hh

@@ -268,6 +268,7 @@ public:
     auto patternBuilder = matrixBackend.patternBuilder();
     assembleBulkPattern(patternBuilder);
     patternBuilder.setupMatrix();
+    matrixBackend.assign(0);
     assembleBulkEntries(matrixBackend, std::forward<LocalAssembler>(localAssembler));
   }
 

dune/fufem/assemblers/istlbackend.hh

@@ -311,6 +311,31 @@ public:
     return i(*matrix_);
   }
 
+  /**
+   * \brief Const access to wrapped matrix
+   */
+  const Matrix& matrix() const
+  {
+    return *matrix_;
+  }
+
+  /**
+   * \brief Mutable access to wrapped matrix
+   */
+  Matrix& matrix()
+  {
+    return *matrix_;
+  }
+
+  /**
+   * \brief Assign value to wrapped matrix
+   */
+  template<class Value>
+  void assign(const Value& value)
+  {
+    matrix() = value;
+  }
+
 protected:
 
   Matrix* matrix_;