helper module to set up RNG-function injection

CMakeLists.txt

@@ -251,6 +251,7 @@ add_subdirectory (documentation)
 #
 set (CORSIKA_DATA_WITH_TEST ON) # we want to run the corsika-data unit test
 add_subdirectory (modules/data) # this is corsika-data (submodule)
+add_subdirectory (modules/common)
 add_subdirectory (modules/pythia8)
 add_subdirectory (modules/sibyll)
 add_subdirectory (modules/sophia)

modules/common/CMakeLists.txt

+add_library (modules_common INTERFACE)
+
+
+target_include_directories (
+  modules_common
+  INTERFACE
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+  $<INSTALL_INTERFACE:include/corsika_modules/common>
+  )
+
+install (
+  FILES
+  rng_decl.hpp rng_impl.gpp
+  DESTINATION include/corsika_modules/common
+  )
+
+install (
+  TARGETS modules_common
+  EXPORT CORSIKA8PublicTargets
+  ARCHIVE DESTINATION lib/corsika
+  LIBRARY DESTINATION lib/corsika # just for cmake 3.10.x (ubuntu 18)
+  )
+
+# add sibyll to corsika8 build
+add_dependencies (CORSIKA8 modules_common)
+target_link_libraries (CORSIKA8 INTERFACE modules_common)

modules/common/rng_decl.hpp

+/*
+ * (c) Copyright 2023 CORSIKA Project, corsika-project@lists.kit.edu
+ *
+ * This software is distributed under the terms of the GNU General Public
+ * Licence version 3 (GPL Version 3). See file LICENSE for a full version of
+ * the license.
+ */
+
+#pragma once
+
+#include <functional>
+
+#define DECLARE_RNG(NAME) \
+namespace NAME { \
+void set_rng_function(std::function<void(double*, std::size_t)>); \
+} \
+extern "C" void set_##NAME##_rng_function(void (*rng_function)(double*, std::size_t));

modules/common/rng_impl.hpp

+/*
+ * (c) Copyright 2023 CORSIKA Project, corsika-project@lists.kit.edu
+ *
+ * This software is distributed under the terms of the GNU General Public
+ * Licence version 3 (GPL Version 3). See file LICENSE for a full version of
+ * the license.
+ */
+
+#pragma once
+
+#include <array>
+#include <functional>
+#include <iterator>
+#include <iostream>
+
+alignas(64) static std::array<double, 16> random_buffer{}; // aligned to fill two cache lines
+static std::function<void(double*, size_t)> rng_ptr = nullptr;
+static double const* next_rand = std::next(random_buffer.data(), random_buffer.size());
+
+#define IMPLEMENT_RNG(NAME) \
+namespace NAME { \
+void set_rng_function(std::function<void(double*, size_t)> rng_function) { \
+  rng_ptr = rng_function; \
+} \
+} \
+extern "C" void set_##NAME##_rng_function(void (*rng_function)(double*, size_t)) { \
+  NAME::set_rng_function(std::function{rng_function}); \
+}
+
+static double draw_std_rnd() {
+  if (next_rand == std::next(random_buffer.data(), random_buffer.size())) {
+    // no more unused values in buffer, refill via injected RNG function
+    rng_ptr(random_buffer.data(), random_buffer.size());
+    next_rand = random_buffer.data();
+  }
+
+  return *next_rand++;
+}