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I want my CMake project to be built by make -j N, whenever I call make from the terminal. I don't want to set -j option manually every time.
For that, I set CMAKE_MAKE_PROGRAM variable to the specific command line. I use the ProcessorCount() function, which gives the number of procesors to perform build in parallel.
When I do make, I do not see any speed up. However if I do make -j N, then it is built definitely faster.
Would you please help me on this issue? (I am developing this on Linux.)
Here is the snippet of the code that I use in CMakeList.txt:
include(ProcessorCount)
ProcessorCount(N)
message("number of processors: " ${N})
if(NOT N EQUAL 0)
set(CTEST_BUILD_FLAGS -j${N})
set(ctest_test_args ${ctest_test_args} PARALLEL_LEVEL ${N})
set(CMAKE_MAKE_PROGRAM "${CMAKE_MAKE_PROGRAM} -j ${N}")
endif()
message("cmake make program" ${CMAKE_MAKE_PROGRAM})
Thank you very much.
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When CMake is first run in an empty build tree, it creates a CMakeCache. txt file and populates it with customizable settings for the project. This option may be used to specify a setting that takes priority over the project's default value. The option may be repeated for as many CACHE entries as desired.
Options and variables are defined on the CMake command line like this: $ cmake -DVARIABLE=value path/to/source You can set a variable after the initial `CMake` invocation to change its value. You can also undefine a variable: $ cmake -UVARIABLE path/to/source Variables are stored in the `CMake` cache.
Running CMake from the command line From the command line, cmake can be run as an interactive question and answer session or as a non-interactive program. To run in interactive mode, just pass the option “-i” to cmake. This will cause cmake to ask you to enter a value for each value in the cache file for the project.
Run make anywhere Once you have run cmake, you do not need to run it again unless a) you create another build directory or b) your current build directory is destroyed or horribly broken. In either of these cases, follow the steps above and run cmake in the top level build directory.
In case you want to speed up the build you can run multiple make processes in parallel but not cmake. To perform every build with predefined number of parallel processes you can define this in MAKEFLAGS.
Set MAKEFLAGS in your environment script, e.g. ~/.bashrc as you want:
export MAKEFLAGS=-j8
On Linux the following sets MAKEFLAGS to the number of CPU - 1: (Keep one CPU free for other tasks while build) and is useful in environments with dynamic ressources, e.g. VMware:
export MAKEFLAGS=-j$(($(grep -c "^processor" /proc/cpuinfo) - 1))
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