[CMake] How to get custom commands to build in parallel ?

[Glenn Coombs]

I am already using /MP and the equivalent to the /maxcpucount.  It is the
/MP one that is important in this context as I am only concerned with
improving the speed of a single project out of the many in my solution.  I
believe the problem is with cmake rather than with Visual Studio as I can
select any of the other projects in the same solution and build them in
isolation and they will build their object files in parallel.  For some
reason cmake isn't seeing the custom commands as something it can run in
parallel.

--
Glenn

On 23 September 2014 16:20, Robert Maynard <robert.maynard at kitware.com>
wrote:

> If you are using VS2013 you should look at the /maxcpucount flag which
> allows msbuild to build multiple projects at the same time. You will
> have to manually balance /MP and /maxcpucount as they cause a P*C
> number of processes to execute.
>
> On Tue, Sep 23, 2014 at 11:05 AM, Glenn Coombs <glenn.coombs at gmail.com>
> wrote:
> > I have the following code in one of my CMakeLists.txt files:
> >
> > set(feature_files_h)
> > set(feature_files_cpp)
> >
> > macro(create_feature_files NAME)
> >     add_custom_command(
> >         OUTPUT ${FEATURES_OUTPUT_DIR}/${NAME}.cpp
> > ${FEATURES_OUTPUT_DIR}/${NAME}.h
> >         DEPENDS ${FEATURES_INPUT_DIR}/${NAME}.txt
> >         WORKING_DIRECTORY ${SIM_ROOT}/tools/features
> >         COMMAND perl ${FEATURES_PERL_PATH} "-s${FEATURES_INPUT_DIR}"
> > "-d${FEATURES_OUTPUT_DIR}" "-f${NAME}"
> >         )
> >     list(APPEND feature_files_h   ${FEATURES_OUTPUT_DIR}/${NAME}.h)
> >     list(APPEND feature_files_cpp ${FEATURES_OUTPUT_DIR}/${NAME}.cpp)
> > endmacro()
> >
> > create_feature_files(example_features)
> > create_feature_files(fme_core_features)
> > create_feature_files(fme_features)
> > create_feature_files(front_end_features)
> > create_feature_files(inloop_filter_features)
> >
> > add_library(${PROJECT_NAME} STATIC ${feature_files_cpp}
> ${feature_files_h}
> > ${SIM_ROOT}/tools/features/cpp-code/cfeatures.cpp)
> >
> > which creates a library from an existing source file called cfeatures.cpp
> > and from a bunch of auto-generated .cpp and .h files.  The whole thing
> works
> > fine and runs the perl script to create each of the auto-generated files
> > before creating the library.  The only problem I have with it is that it
> is
> > quite slow and I would like to speed it up by having it run the perl
> > commands to create the auto-generated files in parallel.  Currently,
> each of
> > the auto-generated cpp files is generated sequentially, then they are all
> > compiled in parallel and the library created in the final step.
> >
> > I'm using cmake 3.0.0 with Visual Studio 2013 Express Edition.  And I've
> > added the /MP option so that Visual Studio will do parallel builds.  I've
> > also set the "Projects and Solutions=>Build and Run=>maximum number of
> > parallel project builds" option to 4.  This works well with all the
> normal
> > cpp files in other projects and I easily see all 4 cpu cores maxxed out.
> > But when building this project only 1 cpu core is used.
> >
> > Can anybody tell me how to change it so that the auto-geneated files are
> > created in parallel as well ?
> >
> > --
> > Glenn
> >
> >
> > --
> >
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