diff --git a/CMakeLists.txt b/CMakeLists.txt
index a82722c0..23b1d35e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -20,6 +20,7 @@ OPTION(ARCH_ARM64 "MacOS arch arm64" OFF)
 OPTION(APPLE_ACC_SINGLE_PREC "Fix Apple Accelerate single prec" ON)
 OPTION(BUILD_LIB "Build python block2.so" OFF)
 OPTION(BUILD_CLIB "Build C++ block2.so" OFF)
+OPTION(BUILD_EXECUTABLE "Build executable block2" ON)
 OPTION(FORCE_LIB_ABS_PATH "Using absolute path when linking libraries" ON)
 OPTION(USE_PCH "Use precompiled headers for faster builds" OFF)
 
@@ -593,8 +594,19 @@ ENDIF()
 
 SET(B2_TARGETS "")
 
+
+ADD_LIBRARY(b2_core OBJECT ${SRCS})
+IF(${USE_PCH})
+    # these will be precompiled if USE_PCH is ON
+    FILE(GLOB COREHDRS src/instantiation/*.hpp)
+    TARGET_PRECOMPILE_HEADERS(b2_core PRIVATE ${COREHDRS})
+ENDIF()
+LIST(APPEND B2_TARGETS b2_core)
+
+
+
 IF (${BUILD_LIB})
-    ADD_LIBRARY(b2_pylib MODULE ${PYBIND_SRCS} src/pybind.cpp ${SRCS})
+    ADD_LIBRARY(b2_pylib MODULE ${PYBIND_SRCS} src/pybind.cpp $<TARGET_OBJECTS:b2_core>)
     SET_TARGET_PROPERTIES(b2_pylib PROPERTIES SUFFIX "${PYLIB_SUFFIX}" PREFIX "")
     SET_TARGET_PROPERTIES(b2_pylib PROPERTIES OUTPUT_NAME ${PROJECT_NAME})
     LIST(APPEND B2_TARGETS b2_pylib)
@@ -611,26 +623,26 @@ IF (${BUILD_LIB})
         TARGET_LINK_LIBRARIES(b2_pylib PUBLIC ${PYTHON_LIB_X})
     ENDIF()
     IF(${USE_PCH})
-        # these will be precompiled if USE_PCH is ON
-        FILE(GLOB COREHDRS src/instantiation/*.hpp)
-        TARGET_PRECOMPILE_HEADERS(b2_pylib PRIVATE ${COREHDRS})
+        TARGET_PRECOMPILE_HEADERS(b2_pylib REUSE_FROM b2_core)
     ENDIF()
-ELSEIF (${BUILD_TEST})
+ENDIF()
+
+IF (${BUILD_TEST})
     ADD_EXECUTABLE(b2_testexe unit_test/debug_main.cpp)
     SET_TARGET_PROPERTIES(b2_testexe PROPERTIES OUTPUT_NAME ${PROJECT_NAME})
     LIST(APPEND B2_TARGETS b2_testexe)
     IF (NOT(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC"))
         SET(OPT_FLAG ${OPT_FLAG} -Wno-error=attributes -Wno-attributes -Wno-deprecated-declarations)
     ENDIF()
-ELSEIF (${BUILD_CLIB})
-    ADD_LIBRARY(b2_clib SHARED ${SRCS})
+ENDIF()
+
+IF (${BUILD_CLIB})
+    ADD_LIBRARY(b2_clib SHARED $<TARGET_OBJECTS:b2_core>)
     SET_TARGET_PROPERTIES(b2_clib PROPERTIES OUTPUT_NAME ${PROJECT_NAME})
     SET_TARGET_PROPERTIES(b2_clib PROPERTIES POSITION_INDEPENDENT_CODE 1)
 
     IF(${USE_PCH})
-        # these will be precompiled if USE_PCH is ON
-        FILE(GLOB COREHDRS src/instantiation/*.hpp)
-        TARGET_PRECOMPILE_HEADERS(b2_clib PRIVATE ${COREHDRS})
+        TARGET_PRECOMPILE_HEADERS(b2_clib REUSE_FROM b2_core)
     ENDIF()
 
     LIST(APPEND B2_TARGETS b2_clib)
@@ -655,17 +667,19 @@ ELSEIF (${BUILD_CLIB})
     INSTALL(FILES ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
         ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
         DESTINATION "share/cmake/${PROJECT_NAME}")
-ELSE()
+ENDIF()
+
+IF(${BUILD_EXECUTABLE})
     IF (NOT ${USE_DMRG})
         MESSAGE(FATAL_ERROR "-DUSE_DMRG must be ON for compiling src/main.cpp.")
     ENDIF()
-    ADD_EXECUTABLE(b2_exe src/main.cpp ${SRCS})
+    ADD_EXECUTABLE(b2_exe src/main.cpp $<TARGET_OBJECTS:b2_core>)
     SET_TARGET_PROPERTIES(b2_exe PROPERTIES OUTPUT_NAME ${PROJECT_NAME})
+
     IF(${USE_PCH})
-        # these will be precompiled if USE_PCH is ON
-        FILE(GLOB COREHDRS src/instantiation/*.hpp)
-        TARGET_PRECOMPILE_HEADERS(b2_exe PRIVATE ${COREHDRS})
+        TARGET_PRECOMPILE_HEADERS(b2_exe REUSE_FROM b2_core)
     ENDIF()
+
     LIST(APPEND B2_TARGETS b2_exe)
 ENDIF()
 
@@ -734,8 +748,6 @@ FOREACH(tgt ${B2_TARGETS})
     TARGET_LINK_LIBRARIES(${tgt} PRIVATE ${PTHREAD} ${LAPACK_LIBRARIES} ${BLAS_LIBRARIES} ${MKL_LIBS} ${MPI_LIBS} ${TBB_LIBS} ${BLIS_LIBS})
     SET_TARGET_PROPERTIES(${tgt} PROPERTIES LINK_FLAGS "${ARCH_LINK_FLAGS} ${MPI_LINK_FLAGS}")
 
-
-
     TARGET_INCLUDE_DIRECTORIES(${tgt} PUBLIC ${PYTHON_INCLUDE_DIRS} ${PYBIND_INCLUDE_DIRS}
         ${MKL_INCLUDE_DIR} ${MPI_INCLUDE_DIR} ${TBB_INCLUDE_DIR} ${BLIS_INCLUDE_DIR})
     TARGET_COMPILE_OPTIONS(${tgt} BEFORE PRIVATE ${OPT_FLAG} ${ARCH_FLAG})
@@ -758,7 +770,7 @@ IF (${BUILD_TEST})
         SET(OPT_FLAG ${OPT_FLAG} -fcompare-debug-second)
     ENDIF()
 
-    ADD_EXECUTABLE(${PROJECT_NAME}_tests ${TSRCS} ${SRCS})
+    ADD_EXECUTABLE(${PROJECT_NAME}_tests ${TSRCS} $<TARGET_OBJECTS:b2_core>)
     TARGET_INCLUDE_DIRECTORIES(${PROJECT_NAME}_tests PUBLIC src ${MKL_INCLUDE_DIR} ${MPI_INCLUDE_DIR} ${TBB_INCLUDE_DIR} ${BLIS_INCLUDE_DIR})
     TARGET_LINK_LIBRARIES(${PROJECT_NAME}_tests ${GTEST_BOTH_LIBRARIES} ${PTHREAD} ${MPI_LIBS} ${TBB_LIBS} ${BLIS_LIBS})
     TARGET_COMPILE_OPTIONS(${PROJECT_NAME}_tests BEFORE PUBLIC ${ARCH_FLAG} ${OPT_FLAG} ${MKL_FLAG} ${MPI_FLAG}