Create RNG Factory only if it is needed

MySimulation.hpp: - RNGFactory will only be created if it is required by either
                    ionization or the photon creation

UsesRNG.hpp: - PIConGPU trait that checks if an object requires an RNG
             - Default is "false"

FilterByRNG.hpp: - PMacc particle trait that takes a list of species and
                   checks all of them with the UsesRNG trait to create
                   a new list of species.

ADL_Impl: - specialized the UsesRNG trait for "ADK_Impl" to return "true"

Status: compiles [x], runs[x]

src/libPMacc/include/particles/traits/FilterByRNG.hpp

@@ -0,0 +1,66 @@
+/**
+ * Copyright 2016 Marco Garten, Heiko Burau
+ *
+ * This file is part of libPMacc.
+ *
+ * libPMacc is free software: you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License or
+ * the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * libPMacc is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License and the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * and the GNU Lesser General Public License along with libPMacc.
+ * If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "pmacc_types.hpp"
+#include "traits/UsesRNG.hpp"
+#include <boost/mpl/copy_if.hpp>
+#include <boost/mpl/placeholders.hpp>
+
+namespace PMacc
+{
+namespace particles
+{
+namespace traits
+{
+
+/** Return a new sequence of particle species that require random number
+ *  generation for their ionization.
+ *
+ * @tparam T_MPLSeq sequence of particle species
+ *
+ * \TODO rather pass a sequence of objects, like ionization modules
+ */
+template<typename T_MPLSeq>
+struct FilterByRNG
+{
+    typedef T_MPLSeq MPLSeq;
+
+    template<typename T_Species>
+    struct UsesRNG
+    {
+        typedef T_Species SpeciesType;
+        /* SelectIonizer will be either the specified one or fallback: None */
+        typedef typename picongpu::traits::GetIonizer<SpeciesType>::type SelectIonizer;
+        /* check if ionization module requires RNG: type is boost::mpl::bool_<> */
+        typedef typename ::picongpu::traits::UsesRNG<
+            SelectIonizer
+            >::type type;
+    };
+
+    typedef typename bmpl::copy_if<MPLSeq, UsesRNG<bmpl::_> >::type type;
+};
+
+}//namespace traits
+}//namespace particles
+}//namespace PMacc

src/picongpu/include/particles/ionization/byField/ADK/ADK_Impl.hpp

@@ -22,6 +22,7 @@
 
 #include "simulation_defines.hpp"
 #include "traits/Resolve.hpp"
+#include "traits/UsesRNG.hpp"
 #include "mappings/kernel/AreaMapping.hpp"
 
 #include "fields/FieldB.hpp"
@@ -42,6 +43,17 @@
 
 namespace picongpu
 {
+namespace traits
+{
+
+    template<typename T_IonizationAlgorithm, typename T_DestSpecies, typename T_SrcSpecies>
+    struct UsesRNG<particles::ionization::ADK_Impl<T_IonizationAlgorithm, T_DestSpecies, T_SrcSpecies> >
+    {
+        /* ionization module uses random number generation */
+        typedef boost::mpl::bool_<true> type;
+    };
+} // namespace traits
+
 namespace particles
 {
 namespace ionization

src/picongpu/include/simulationControl/MySimulation.hpp

@@ -66,6 +66,7 @@
 #include "particles/InitFunctors.hpp"
 #include "particles/memory/buffers/MallocMCBuffer.hpp"
 #include "particles/traits/FilterByFlag.hpp"
+#include "particles/traits/FilterByRNG.hpp"
 #include "particles/IdProvider.hpp"
 
 #include <boost/mpl/int.hpp>
@@ -285,17 +286,32 @@ class MySimulation : public SimulationHelper<simDim>
 
         laser = new LaserPhysics(cellDescription->getGridLayout());
 
+        // Make a list of all species that can be ionized
+        typedef typename PMacc::particles::traits::FilterByFlag
+        <
+            VectorAllSpecies,
+            ionizer<>
+        >::type VectorSpeciesWithIonizer;
+
+        // filter the list of ionized species for those that require random number generation
+        typedef typename PMacc::particles::traits::FilterByRNG<VectorSpeciesWithIonizer>::type VectorSpeciesRequiringRNG;
+
         // Initialize random number generator and synchrotron functions, if there are synchrotron photon species
         typedef typename PMacc::particles::traits::FilterByFlag<VectorAllSpecies,
                                                                 synchrotronPhotons<> >::type AllSynchrotronPhotonsSpecies;
-        if(!bmpl::empty<AllSynchrotronPhotonsSpecies>::value)
+
+        if(!bmpl::empty<AllSynchrotronPhotonsSpecies>::value || !bmpl::empty<VectorSpeciesRequiringRNG>::value)
         {
             // create factory for the random number generator
             this->rngFactory = new RNGFactory(Environment<simDim>::get().SubGrid().getLocalDomain().size);
             // init factory
             PMacc::GridController<simDim>& gridCon = PMacc::Environment<simDim>::get().GridController();
             this->rngFactory->init(gridCon.getScalarPosition());
+        }
 
+        // Initialize synchrotron functions, if there are synchrotron photon species
+        if(!bmpl::empty<AllSynchrotronPhotonsSpecies>::value)
+        {
             this->synchrotronFunctions.init();
         }
 

src/picongpu/include/traits/UsesRNG.hpp

@@ -0,0 +1,52 @@
+/**
+ * Copyright 2016 Marco Garten, Rene Widera
+ *
+ * This file is part of PIConGPU.
+ *
+ * PIConGPU is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * PIConGPU is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with PIConGPU.
+ * If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <boost/mpl/bool.hpp>
+
+namespace picongpu
+{
+namespace traits
+{
+
+/** Checks if an object requires the RNG
+ *
+ * @tparam T_Object any object (class or typename)
+ *
+ * This struct must define
+ * ::type (boost::mpl::bool_<>)
+ */
+template<typename T_Object>
+struct UsesRNG
+{
+    /* default implementation */
+    typedef boost::mpl::bool_<false> type;
+};
+
+template<typename T_Object>
+bool usesRNG(const T_Object& obj)
+{
+    return UsesRNG<T_Object>::type::value;
+}
+
+}// namespace traits
+
+}// namespace picongpu