support for runtime dlopen

src/ngraph/CMakeLists.txt

@@ -130,6 +130,27 @@ if (NGRAPH_CPU_ENABLE AND LLVM_INCLUDE_DIR AND
 endif()
 
 add_library(ngraph SHARED ${SRC})
+
+# Colon separated string for specified runtime plugin loading, this is made explicit s.t. if a
+# plugin is specified at compile time but the corresponding library could not be resolved at run-
+# time, an error will be generated.
+# E.g. assume compiling with Argon and Xpu, then -DRUNTIME_PLUGIN_LIBS="libargon.so:libxpu.so".
+if (RUNTIME_PLUGIN_LIBS)
+    target_compile_definitions(ngraph PRIVATE RUNTIME_PLUGIN_LIBS=${RUNTIME_PLUGIN_LIBS})
+else()
+    target_compile_definitions(ngraph PRIVATE RUNTIME_PLUGIN_LIBS="")
+endif()
+
+# This is used to ensure that libngraph.so and libargon.so are in the same directory for dlopen.
+# Effective at build time. Does not affect `make install` logics.
+if (COMMON_LIBRARY_OUTPUT_DIRECTORY)
+    set_target_properties(ngraph PROPERTIES
+        LIBRARY_OUTPUT_DIRECTORY ${COMMON_LIBRARY_OUTPUT_DIRECTORY})
+    message(STATUS "LIBRARY_OUTPUT_DIRECTORY set to: ${COMMON_LIBRARY_OUTPUT_DIRECTORY}")
+else()
+    message(STATUS "LIBRARY_OUTPUT_DIRECTORY not set, will use the defualt value")
+endif()
+
 target_include_directories(ngraph PUBLIC "${NGRAPH_INCLUDE_PATH}")
 
 if(NGRAPH_CPU_ENABLE AND LLVM_LINK_LIBS)
@@ -146,6 +167,7 @@ if(NGRAPH_CPU_ENABLE AND MKLDNN_LIB_DIR)
     target_link_libraries(ngraph LINK_PRIVATE mkldnn)
 endif()
 
+
 #-----------------------------------------------------------------------------------------------
 # Installation logic...
 #-----------------------------------------------------------------------------------------------

src/ngraph/runtime/manager.cpp

@@ -13,12 +13,53 @@
 // ----------------------------------------------------------------------------
 
 #include "ngraph/runtime/manager.hpp"
+#include <dlfcn.h>
+#include <iostream>
+#include <sstream>
+#include <string>
 
 using namespace ngraph::runtime;
 
+bool Manager::load_plugins(const std::string& runtime_plugin_libs)
+{
+    std::istringstream ss(runtime_plugin_libs);
+    std::string plugin_lib_path;
+
+    while (std::getline(ss, plugin_lib_path, ':'))
+    {
+        if (plugin_lib_path.size() > 0)
+        {
+            void* lib_handle = dlopen(plugin_lib_path.c_str(), RTLD_NOW);
+            if (!lib_handle)
+            {
+                std::cerr << "Cannot open library: " << plugin_lib_path << ", " << dlerror()
+                          << std::endl;
+                return false;
+            }
+            else
+            {
+                std::cerr << "Loaded runtime at " << lib_handle << std::endl;
+            }
+        }
+    }
+    return true;
+}
+
 Manager::FactoryMap& Manager::get_factory_map()
 {
+    // Stores Manager Factories
     static FactoryMap factory_map;
+
+    // Try to load runtime plugins
+    if (!Manager::m_is_factory_map_initialized)
+    {
+        if (!Manager::load_plugins(RUNTIME_PLUGIN_LIBS))
+        {
+            std::cerr << "Failed to load at least one of the following libraries: "
+                      << RUNTIME_PLUGIN_LIBS << std::endl;
+        }
+        Manager::m_is_factory_map_initialized = true;
+    }
     return factory_map;
 }
 
@@ -32,3 +73,5 @@ Manager::Factory Manager::register_factory(std::string name, Factory factory)
     get_factory_map()[name] = factory;
     return factory;
 }
+
+bool Manager::m_is_factory_map_initialized = false;

src/ngraph/runtime/manager.hpp

@@ -46,13 +46,19 @@ namespace ngraph
                 compile(const std::shared_ptr<ngraph::Function>& fun) = 0;
 
             using Factory = std::function<std::shared_ptr<Manager>(const std::string&)>;
-            using FactoryMap = std::map<std::string, Factory>;
-
-            static FactoryMap& get_factory_map();
 
             static std::shared_ptr<Manager> get(const std::string& name);
 
             static Factory register_factory(std::string name, Factory factory);
+
+        private:
+            static bool load_plugins(const std::string& runtime_plugin_libs);
+
+            static bool m_is_factory_map_initialized;
+
+            using FactoryMap = std::map<std::string, Factory>;
+
+            static FactoryMap& get_factory_map();
         };
     }
 }