ros(22):catkin_make可以加多线程/多核、catkin_make -j4、catkin_make -j8、catkin_make -j12、catkin_make -j16_invoking "make -j4 -l4" failed

        之前以为catkin_make 后面不能加多核/多线程，现在发现是可以的，catkin_make -jn（n为数字）命令在编译时被拆分为以下两个：

make cmake_check_build_system
 
make -jn

而且可以使用：

catkin_make --pkg packagename -jn
#就是编译指定包也可以使用多核/多线程

而且比使用catkin_make会快一些（有时候会快很多，取决于上面两条命令中的make -jn）

        下面以catkin_make -j16为例进行演示：

meng@meng:~/ideas/ros_ws$ catkin_make -j16
Base path: /home/meng/ideas/ros_ws
Source space: /home/meng/ideas/ros_ws/src
Build space: /home/meng/ideas/ros_ws/build
Devel space: /home/meng/ideas/ros_ws/devel
Install space: /home/meng/ideas/ros_ws/install
####
#### Running command: "cmake /home/meng/ideas/ros_ws/src -DCATKIN_DEVEL_PREFIX=/home/meng/ideas/ros_ws/devel -DCMAKE_INSTALL_PREFIX=/home/meng/ideas/ros_ws/install -G Unix Makefiles" in "/home/meng/ideas/ros_ws/build"
####
-- The C compiler identification is GNU 7.5.0
-- The CXX compiler identification is GNU 7.5.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Using CATKIN_DEVEL_PREFIX: /home/meng/ideas/ros_ws/devel
-- Using CMAKE_PREFIX_PATH: /opt/ros/melodic
-- This workspace overlays: /opt/ros/melodic
-- Found PythonInterp: /usr/bin/python2 (found suitable version "2.7.17", minimum required is "2") 
-- Using PYTHON_EXECUTABLE: /usr/bin/python2
-- Using Debian Python package layout
-- Using empy: /usr/bin/empy
-- Using CATKIN_ENABLE_TESTING: ON
-- Call enable_testing()
-- Using CATKIN_TEST_RESULTS_DIR: /home/meng/ideas/ros_ws/build/test_results
-- Forcing gtest/gmock from source, though one was otherwise available.
-- Found gtest sources under '/usr/src/googletest': gtests will be built
-- Found gmock sources under '/usr/src/googletest': gmock will be built
-- Found PythonInterp: /usr/bin/python2 (found version "2.7.17") 
-- Found Threads: TRUE  
-- Using Python nosetests: /usr/bin/nosetests-2.7
-- catkin 0.7.29
-- BUILD_SHARED_LIBS is on
-- BUILD_SHARED_LIBS is on
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- ~~  traversing 1 packages in topological order:
-- ~~  - using_markers
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- +++ processing catkin package: 'using_markers'
-- ==> add_subdirectory(using_markers)
-- Configuring done
-- Generating done
-- Build files have been written to: /home/meng/ideas/ros_ws/build
####
#### Running command: "make -j16" in "/home/meng/ideas/ros_ws/build"
####
Scanning dependencies of target basic_shapes
[ 50%] Building CXX object using_markers/CMakeFiles/basic_shapes.dir/src/basic_shapes.cpp.o
[100%] Linking CXX executable /home/meng/ideas/ros_ws/devel/lib/using_markers/basic_shapes
[100%] Built target basic_shapes