Add option to disable Libxc backend upon request

CMakeLists.txt

@@ -9,6 +9,7 @@ option( EXCHCXX_ENABLE_BENCHMARK "Enable Performance Benchmark" OFF )
 option( EXCHCXX_ENABLE_CUDA      "Enable Device Code (CUDA)"    OFF )
 option( EXCHCXX_ENABLE_HIP       "Enable Device Code (HIP)"     OFF )
 option( EXCHCXX_ENABLE_SYCL      "Enable Device Code (SYCL)"    OFF )
+option( EXCHCXX_ENABLE_LIBXC     "Enable Libxc Backend"         ON  )
 option( BUILD_SHARED_LIBS        "Build Shared Libs"            OFF )
 
 
@@ -53,6 +54,7 @@ if( EXCHCXX_ENABLE_HIP )
 endif()
 
 
+if(EXCHCXX_ENABLE_LIBXC)
 
 ## Find LibXC
 find_package( Libxc 6.2.0 CONFIG QUIET )
@@ -96,6 +98,10 @@ else()
   set( BUILD_TESTING ${OLD_BUILD_TESTING} CACHE BOOL "" FORCE )
 
 endif()
+
+else( EXCHCXX_ENABLE_LIBXC )
+  set( Libxc_FOUND FALSE )
+endif( EXCHCXX_ENABLE_LIBXC )
 
 add_subdirectory( src )
 
@@ -105,13 +111,13 @@ if( NOT DEFINED EXCHCXX_ENABLE_TESTS )
 endif()
 
 if( CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME AND EXCHCXX_ENABLE_TESTS AND BUILD_TESTING )
-  if(${Libxc_FOUND})
+  if(${Libxc_FOUND} OR NOT EXCHCXX_ENABLE_LIBXC)
     message(WARNING "ExchCXX Unit Tests Require Local Patch of Libxc - Disabling")
   else()
     add_subdirectory( test )
   endif()
 endif()
 
-if( EXCHCXX_ENABLE_BENCHMARK )
+if( EXCHCXX_ENABLE_BENCHMARK AND EXCHCXX_ENABLE_LIBXC )
   add_subdirectory( performance )
 endif()

cmake/ExchCXXConfig.cmake.in

@@ -4,13 +4,17 @@ get_filename_component(ExchCXX_CMAKE_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
 
 list(APPEND CMAKE_MODULE_PATH ${ExchCXX_CMAKE_DIR})
 include(CMakeFindDependencyMacro)
-find_dependency( Libxc @Libxc_VERSION@ EXACT CONFIG )
 
 
 set( EXCHCXX_ENABLE_CUDA   @EXCHCXX_ENABLE_CUDA@   )
 set( EXCHCXX_ENABLE_HIP    @EXCHCXX_ENABLE_HIP@    )
 set( EXCHCXX_ENABLE_SYCL   @EXCHCXX_ENABLE_SYCL@   )
 set( EXCHCXX_ENABLE_DEVICE @EXCHCXX_ENABLE_DEVICE@ )
+set( EXCHCXX_ENABLE_LIBXC  @EXCHCXX_ENABLE_LIBXC@  )
+
+if( EXCHCXX_ENABLE_LIBXC )
+  find_dependency( Libxc @Libxc_VERSION@ EXACT CONFIG )
+endif()
 
 if( EXCHCXX_ENABLE_CUDA )
   find_dependency( CUDAToolkit @CUDAToolkit_VERSION@ EXACT )

include/exchcxx/enums/backend.hpp

@@ -49,10 +49,14 @@
 namespace ExchCXX {
 
 enum class Backend {
+#ifdef EXCHCXX_ENABLE_LIBXC
   libxc,
+#endif
   builtin
 };
 
+#ifdef EXCHCXX_ENABLE_LIBXC
 using libxc_name_string = detail::NamedType<std::string, struct LibxcNameString>;
+#endif
 
 }

include/exchcxx/exchcxx_config.hpp.in

@@ -49,6 +49,7 @@
 #cmakedefine EXCHCXX_ENABLE_HIP
 #cmakedefine EXCHCXX_ENABLE_SYCL
 #cmakedefine EXCHCXX_ENABLE_DEVICE
+#cmakedefine EXCHCXX_ENABLE_LIBXC
 
 
 #ifdef EXCHCXX_ENABLE_CUDA

include/exchcxx/factory/xc_kernel.hpp

@@ -54,17 +54,22 @@
 
 namespace ExchCXX {
 
+#ifdef EXCHCXX_ENABLE_LIBXC
 XCKernel libxc_kernel_factory(const Kernel, const Spin );
 XCKernel libxc_kernel_factory(const std::string xc_name, const Spin polar );
+#endif
+
 XCKernel builtin_kernel_factory( Kernel, Spin );
 
 static inline XCKernel kernel_factory( 
   Backend backend, Kernel kern, Spin polar
 ) {
 
+#ifdef EXCHCXX_ENABLE_LIBXC
   if( backend == Backend::libxc )
     return libxc_kernel_factory( kern, polar );
   else
+#endif
     return builtin_kernel_factory( kern, polar );
 
 }

include/exchcxx/xc_functional.hpp

@@ -108,7 +108,11 @@ class XCFunctional {
 
   XCFunctional( const Backend, const Functional, const Spin );
   XCFunctional( const Functional func, const Spin polar) :
+#ifdef EXCHCXX_ENABLE_LIBXC
     XCFunctional( Backend::libxc, func, polar) { };
+#else
+    XCFunctional( Backend::builtin, func, polar) { };
+#endif
 
   XCFunctional( const XCFunctional& )                    ;
   XCFunctional( XCFunctional&& )                 noexcept;

include/exchcxx/xc_kernel.hpp

@@ -79,10 +79,15 @@ class XCKernel {
 
   XCKernel( const Backend backend, const Kernel kern, 
     const Spin polar );
+#ifdef EXCHCXX_ENABLE_LIBXC
   XCKernel( const libxc_name_string& xc_name, 
     const Spin polar );
   XCKernel( const Kernel kern, const Spin polar ) : 
     XCKernel( Backend::libxc, kern, polar ){ };
+#else
+  XCKernel( const Kernel kern, const Spin polar ) : 
+    XCKernel( Backend::builtin, kern, polar ){ };
+#endif
 
   XCKernel( impl_ptr&& ptr )                     ;
   XCKernel( const XCKernel& )                    ;

src/CMakeLists.txt

@@ -1,22 +1,24 @@
-
-
-
 set( EXCHCXX_SOURCES
      xc_kernel.cxx
      xc_functional.cxx
-     libxc.cxx
      boilerplate.cxx
      builtin.cxx
      builtin_interface.cxx
      builtin_kernel.cxx
 )
+if(EXCHCXX_ENABLE_LIBXC)
+  list(APPEND EXCHCXX_SOURCES libxc.cxx)
+endif()
+message(STATUS ${EXCHCXX_SOURCES})
 
 add_library( exchcxx ${EXCHCXX_SOURCES} )
 
 # TARGET properties
 
 target_compile_features( exchcxx PUBLIC cxx_std_17 )
-target_link_libraries( exchcxx PUBLIC Libxc::xc )
+if( EXCHCXX_ENABLE_LIBXC )
+  target_link_libraries( exchcxx PUBLIC Libxc::xc )
+endif()
 
 # Generate exchcxx_config.hpp
 configure_file(

src/cuda/exchcxx_cuda.cmake

@@ -1,8 +1,10 @@
 set( EXCHCXX_CUDA_SOURCES 
   cuda/xc_functional_device.cu 
-  cuda/libxc_device.cxx 
   cuda/builtin.cu 
 )
+if( EXCHCXX_ENABLE_LIBXC )
+  list(APPEND EXCHCXX_CUDA_SOURCES cuda/libxc_device.cxx)
+endif()
 
 find_package( CUDAToolkit REQUIRED )
 #add_library( exchcxx_device OBJECT ${EXCHCXX_CUDA_SOURCES} )

src/hip/exchcxx_hip.cmake

@@ -1,8 +1,10 @@
 set( EXCHCXX_HIP_SOURCES 
   hip/xc_functional_device.hip 
-  hip/libxc_device.hip 
   hip/builtin.hip
 )
+if( EXCHCXX_ENABLE_LIBXC )
+  list(APPEND EXCHCXX_HIP_SOURCES hip/libxc_device.hip)
+endif()
 
 find_package( hip REQUIRED )
 

src/sycl/exchcxx_sycl.cmake

@@ -1,8 +1,10 @@
 set( EXCHCXX_SYCL_SOURCES
   sycl/xc_functional_device.cxx
-  sycl/libxc_device.cxx
   sycl/builtin_sycl.cxx
 )
+if( EXCHCXX_ENABLE_LIBXC )
+  list(APPEND EXCHCXX_SYCL_SOURCES sycl/libxc_device.cxx)
+endif()
 
 
 target_sources( exchcxx PRIVATE ${EXCHCXX_SYCL_SOURCES} )

src/xc_kernel.cxx

@@ -92,10 +92,12 @@ XCKernel::XCKernel(
   const Spin polar) : 
 XCKernel( kernel_factory( backend, kern, polar ) ) { }
 
+#ifdef EXCHCXX_ENABLE_LIBXC
 XCKernel::XCKernel(
   const libxc_name_string& xc_name,
   const Spin polar) :
 XCKernel( libxc_kernel_factory( xc_name.get(), polar ) ) { }
+#endif
 
 
 XCKernel::XCKernel( impl_ptr&& ptr ) :