[functions] add ElementwiseDiameterFunction

dune/xt/functions/elementwise-diameter.hh

+// This file is part of the dune-xt project:
+//   https://github.com/dune-community/dune-xt
+// Copyright 2009-2020 dune-xt developers and contributors. All rights reserved.
+// License: Dual licensed as BSD 2-Clause License (http://opensource.org/licenses/BSD-2-Clause)
+//      or  GPL-2.0+ (http://opensource.org/licenses/gpl-license)
+//          with "runtime exception" (http://www.dune-project.org/license.html)
+// Authors:
+//   Felix Schindler (2020)
+
+#ifndef DUNE_XT_FUNCTIONS_ELEMENTWISE_DIAMETER_HH
+#define DUNE_XT_FUNCTIONS_ELEMENTWISE_DIAMETER_HH
+
+#include <dune/xt/functions/interfaces/grid-function.hh>
+
+namespace Dune {
+namespace XT {
+namespace Functions {
+
+
+template <class E>
+class ElementwiseDiameterFunction : public GridFunctionInterface<E>
+{
+  using ThisType = ElementwiseDiameterFunction;
+  using BaseType = GridFunctionInterface<E>;
+
+  class LocalFunction : public XT::Functions::ElementFunctionInterface<E>
+  {
+    using BaseType = XT::Functions::ElementFunctionInterface<E>;
+
+  public:
+    using typename BaseType::DerivativeRangeReturnType;
+    using typename BaseType::DomainType;
+    using typename BaseType::ElementType;
+    using typename BaseType::RangeReturnType;
+
+    LocalFunction()
+      : BaseType()
+      , diameter_(0)
+    {}
+
+  protected:
+    void post_bind(const ElementType& element) override final
+    {
+      diameter_ = Grid::diameter(element);
+    }
+
+  public:
+    int order(const XT::Common::Parameter& /*param*/ = {}) const override final
+    {
+      return 0;
+    }
+
+    RangeReturnType evaluate(const DomainType& /*xx*/, const XT::Common::Parameter& /*param*/ = {}) const override final
+    {
+      return diameter_;
+    }
+
+    DerivativeRangeReturnType jacobian(const DomainType& /*xx*/,
+                                       const XT::Common::Parameter& /*param*/ = {}) const override final
+    {
+      return DerivativeRangeReturnType();
+    }
+
+  private:
+    double diameter_;
+  }; // class LocalFunction
+
+public:
+  using BaseType::d;
+  using BaseType::r;
+  using BaseType::rC;
+  using typename BaseType::LocalFunctionType;
+
+  ElementwiseDiameterFunction(const std::string nm = "ElementwiseDiameterFunction")
+    : BaseType()
+    , name_(nm)
+  {}
+
+  std::unique_ptr<LocalFunctionType> local_function() const override final
+  {
+    return std::make_unique<LocalFunction>();
+  }
+
+  std::string name() const override final
+  {
+    return name_;
+  }
+
+private:
+  std::string name_;
+}; // class ElementwiseDiameterFunction
+
+
+} // namespace Functions
+} // namespace XT
+} // namespace Dune
+
+#endif // DUNE_XT_FUNCTIONS_ELEMENTWISE_DIAMETER_HH