Update cpp_easygraph/CMakeLists.txt: optional deps and safe target linking

Author: Nianle-Li

cpp_easygraph/CMakeLists.txt

@@ -13,63 +13,55 @@ add_subdirectory(pybind11)
 
 option(EASYGRAPH_ENABLE_GPU "EASYGRAPH_ENABLE_GPU" OFF)
 
-# 启用OpenMP支持
+# Find OpenMP (optional)
 find_package(OpenMP)
 if(OpenMP_CXX_FOUND)
     message(STATUS "Found OpenMP: ${OpenMP_CXX_VERSION}")
-    message(STATUS "OpenMP flags: ${OpenMP_CXX_FLAGS}")
 else()
-    message(WARNING "OpenMP not found. Parallel optimization will be disabled.")
+    message(STATUS "OpenMP not found; continuing without OpenMP")
 endif()
 
-# 查找ARPACK库（兼容无CMake配置的系统）
-find_library(ARPACK_LIB NAMES arpack arpack_double PATHS ENV LD_LIBRARY_PATH)
-if(NOT ARPACK_LIB)
-    message(FATAL_ERROR "ARPACK library not found")
-else()
+# Find ARPACK (optional; do not fail if absent)
+find_library(ARPACK_LIB NAMES arpack arpack_double)
+if(ARPACK_LIB)
     message(STATUS "Found ARPACK library: ${ARPACK_LIB}")
+    add_compile_definitions(HAVE_ARPACK=1)
+else()
+    message(WARNING "ARPACK not found; ARPACK-based solvers will be disabled (fallback used).")
+    add_compile_definitions(HAVE_ARPACK=0)
 endif()
 
 find_package(LAPACK REQUIRED)
 
-if (EASYGRAPH_ENABLE_GPU)
-
-    pybind11_add_module(cpp_easygraph
-        ${SOURCES}
-        $<TARGET_OBJECTS:gpu_easygraph>
-    )
-
-    set_property(TARGET cpp_easygraph PROPERTY CUDA_ARCHITECTURES all)
-
-    target_compile_definitions(cpp_easygraph 
-        PRIVATE EASYGRAPH_ENABLE_GPU
-    )
-
-    target_link_libraries(cpp_easygraph
-        PRIVATE cudart_static
-    )
-
-else()
-
-    pybind11_add_module(cpp_easygraph
-        ${SOURCES}
-    )
-
-endif()
-
+# Find Eigen (optional). Change to REQUIRED if Eigen must be enforced.
 find_package(Eigen3 QUIET)
 if(Eigen3_FOUND)
-    message(STATUS "Found Eigen3: ${EIGEN3_INCLUDE_DIR}")
-    include_directories(${EIGEN3_INCLUDE_DIR})
-    add_definitions(-DEIGEN_MAJOR_VERSION=${EIGEN3_VERSION_MAJOR})
-endif()
-
-# 将OpenMP链接到target
-if(OpenMP_CXX_FOUND)
-    target_link_libraries(cpp_easygraph PRIVATE OpenMP::OpenMP_CXX)
-    target_compile_options(cpp_easygraph PRIVATE ${OpenMP_CXX_FLAGS})
-    message(STATUS "OpenMP enabled for cpp_easygraph")
+    message(STATUS "Found Eigen3: ${Eigen3_INCLUDE_DIRS}")
+    add_compile_definitions(HAVE_EIGEN=1)
+else()
+    message(STATUS "Eigen3 not found; eigen-accelerated code will be disabled")
+    add_compile_definitions(HAVE_EIGEN=0)
 endif()
 
-# 链接ARPACK和LAPACK
-target_link_libraries(cpp_easygraph PRIVATE ${ARPACK_LIB} LAPACK::LAPACK)
+# Link/include to cpp_easygraph only if the target exists.
+# This avoids errors when the target is created elsewhere or later.
+if(TARGET cpp_easygraph)
+    if(Eigen3_FOUND)
+        target_include_directories(cpp_easygraph PRIVATE ${Eigen3_INCLUDE_DIRS})
+        if(TARGET Eigen3::Eigen)
+            target_link_libraries(cpp_easygraph PRIVATE Eigen3::Eigen)
+        endif()
+    endif()
+
+    if(OpenMP_CXX_FOUND)
+        target_link_libraries(cpp_easygraph PRIVATE OpenMP::OpenMP_CXX)
+    endif()
+
+    if(ARPACK_LIB)
+        target_link_libraries(cpp_easygraph PRIVATE ${ARPACK_LIB} LAPACK::LAPACK)
+    else()
+        target_link_libraries(cpp_easygraph PRIVATE LAPACK::LAPACK)
+    endif()
+else()
+    message(STATUS "cpp_easygraph target not defined yet; optional libs will be linked after target creation.")
+endif()