Build: Improving CMake performance for finding LibXC and ELPA

CMakeLists.txt

@@ -508,11 +508,8 @@ if(DEFINED Libxc_DIR)
   set(ENABLE_LIBXC ON)
 endif()
 if(ENABLE_LIBXC)
-  find_package(Libxc REQUIRED HINTS
-    ${Libxc_DIR}/share/cmake/Libxc
-    ${Libxc_DIR}/lib/cmake/Libxc
-    ${Libxc_DIR}/lib64/cmake/Libxc
-  )
+  # use `cmake/FindLibxc.cmake` to detect Libxc installation with `pkg-config`
+  find_package(Libxc REQUIRED)
   message(STATUS "Found Libxc: version " ${Libxc_VERSION})
   if(${Libxc_VERSION} VERSION_LESS 5.1.7)
     message(FATAL_ERROR "LibXC >= 5.1.7 is required.")

cmake/FindELPA.cmake

@@ -7,34 +7,49 @@
 #  ELPA_INCLUDE_DIR - Where to find ELPA headers.
 #
 
-find_path(ELPA_INCLUDE_DIR
+find_package(PkgConfig)
+
+if(PKG_CONFIG_FOUND)
+  if(DEFINED ELPA_DIR)
+    string(APPEND CMAKE_PREFIX_PATH ";${ELPA_DIR}")
+  endif()
+  if(USE_OPENMP)
+    pkg_search_module(ELPA REQUIRED IMPORTED_TARGET GLOBAL elpa_openmp)
+  else()
+    pkg_search_module(ELPA REQUIRED IMPORTED_TARGET GLOBAL elpa)
+  endif()
+else()
+  find_path(ELPA_INCLUDE_DIRS
     elpa/elpa.h
     HINTS ${ELPA_DIR}
     PATH_SUFFIXES "include" "include/elpa"
     )
-if(USE_OPENMP)
-    find_library(ELPA_LIBRARY
-        NAMES elpa_openmp elpa
-        HINTS ${ELPA_DIR}
-        PATH_SUFFIXES "lib"
-        )
-else()
-    find_library(ELPA_LIBRARY
-        NAMES elpa
-        HINTS ${ELPA_DIR}
-        PATH_SUFFIXES "lib"
-        )
+  if(USE_OPENMP)
+    find_library(ELPA_LINK_LIBRARIES
+      NAMES elpa_openmp elpa
+      HINTS ${ELPA_DIR}
+      PATH_SUFFIXES "lib"
+      )
+  else()
+    find_library(ELPA_LINK_LIBRARIES
+      NAMES elpa
+      HINTS ${ELPA_DIR}
+      PATH_SUFFIXES "lib"
+      )
+  endif()
+  #message(
+  #  "ELPA : We need pkg-config to get all information about the elpa library")
 endif()
 
 # Handle the QUIET and REQUIRED arguments and
 # set ELPA_FOUND to TRUE if all variables are non-zero.
 include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(ELPA DEFAULT_MSG ELPA_LIBRARY ELPA_INCLUDE_DIR)
+find_package_handle_standard_args(ELPA DEFAULT_MSG ELPA_LINK_LIBRARIES ELPA_INCLUDE_DIRS)
 
 # Copy the results to the output variables and target.
 if(ELPA_FOUND)
-    set(ELPA_LIBRARIES ${ELPA_LIBRARY})
-    set(ELPA_INCLUDE_DIR ${ELPA_INCLUDE_DIR})
+    set(ELPA_LIBRARY ${ELPA_LINK_LIBRARIES})
+    set(ELPA_INCLUDE_DIR ${ELPA_INCLUDE_DIRS})
 
     if(NOT TARGET ELPA::ELPA)
         add_library(ELPA::ELPA UNKNOWN IMPORTED)

cmake/FindLibxc.cmake

@@ -0,0 +1,36 @@
+include(FindPackageHandleStandardArgs)
+
+if(DEFINED Libxc_DIR)
+  string(APPEND CMAKE_PREFIX_PATH ";${Libxc_DIR}")
+endif()
+# Using CMake interface as default.
+# NO REQUIRED here, otherwhile it would throw error
+# with no LibXC found.
+find_package(Libxc HINTS
+    ${Libxc_DIR}/share/cmake/Libxc
+    ${Libxc_DIR}/lib/cmake/Libxc
+    ${Libxc_DIR}/lib64/cmake/Libxc
+  )
+if(NOT TARGET Libxc::xc)
+  find_package(PkgConfig REQUIRED)
+  pkg_search_module(Libxc REQUIRED IMPORTED_TARGET GLOBAL libxc)
+  find_package_handle_standard_args(Libxc DEFAULT_MSG Libxc_LINK_LIBRARIES Libxc_INCLUDE_DIRS)
+endif()
+
+
+# Copy the results to the output variables and target.
+# if find_package() above works, Libxc::xc would be present and
+# below would be skipped.
+if(Libxc_FOUND AND NOT TARGET Libxc::xc)
+	set(Libxc_LIBRARY ${Libxc_LINK_LIBRARIES})
+	set(Libxc_LIBRARIES ${Libxc_LIBRARY})
+	set(Libxc_INCLUDE_DIR ${Libxc_INCLUDE_DIRS})
+	add_library(Libxc::xc UNKNOWN IMPORTED)
+	set_target_properties(Libxc::xc PROPERTIES
+		IMPORTED_LOCATION "${Libxc_LIBRARY}"
+		INTERFACE_INCLUDE_DIRECTORIES "${Libxc_INCLUDE_DIR}")
+endif()
+
+set(CMAKE_REQUIRED_INCLUDES ${CMAKE_REQUIRED_INCLUDES} ${Libxc_INCLUDE_DIR})
+
+mark_as_advanced(Libxc_INCLUDE_DIR Libxc_LIBRARY)

docs/quick_start/easy_install.md

@@ -28,7 +28,7 @@ These requirements support the calculation of plane-wave basis in ABACUS. For LC
 Some of these packages can be installed with popular package management system, such as `apt` and `yum`:
 
 ```bash
-sudo apt update && sudo apt install -y libopenblas-openmp-dev liblapack-dev libscalapack-mpi-dev libelpa-dev libfftw3-dev libcereal-dev libxc-dev g++ make cmake bc git
+sudo apt update && sudo apt install -y libopenblas-openmp-dev liblapack-dev libscalapack-mpi-dev libelpa-dev libfftw3-dev libcereal-dev libxc-dev g++ make cmake bc git pkgconf
 ```
 
 > Installing ELPA by apt only matches requirements on Ubuntu 22.04. For earlier linux distributions, you should build ELPA from source.
@@ -111,12 +111,12 @@ Here, 'build' is the path for building ABACUS; and '-D' is used for setting up s
   - `LAPACK_DIR`: Path to OpenBLAS library `libopenblas.so`(including BLAS and LAPACK)
   - `SCALAPACK_DIR`: Path to ScaLAPACK library `libscalapack.so`
   - `ELPA_DIR`: Path to ELPA install directory; should be the folder containing 'include' and 'lib'.
-  > Note: If you install ELPA from source, please add a symlink to avoid the additional include file folder with version name: `ln -s elpa/include/elpa-2021.05.002/elpa elpa/include/elpa`. This is a known behavior of ELPA.
+  > Note: In ABACUS v3.5.1 or earlier, if you install ELPA from source , please add a symlink to avoid the additional include file folder with version name: `ln -s elpa/include/elpa-2021.05.002/elpa elpa/include/elpa` to help the build system find ELPA headers.
 
   - `FFTW3_DIR`: Path to FFTW3.
   - `CEREAL_INCLUDE_DIR`: Path to the parent folder of `cereal/cereal.hpp`. Will download from GitHub if absent.
   - `Libxc_DIR`: (Optional) Path to Libxc.
-  > Note: Building Libxc from source with Makefile does NOT support using it in CMake here. Please compile Libxc with CMake instead.
+  > Note: In ABACUS v3.5.1 or earlier, Libxc built from source with Makefile is NOT supported; please compile Libxc with CMake instead.
   - `LIBRI_DIR`: (Optional) Path to LibRI.
   - `LIBCOMM_DIR`: (Optional) Path to LibComm.