Add git submodules for picongpu and possible other required projects

[n01r]

When I tried to do the Quickstart from README.md the configureExample.sh failed because it couldn't find picongpu/thirdParty/mallocMC.

To fix this and make ParaTAXIS work even though PMacc and mallocMC steadily evolve a git-submodule should be added. For now in CMakeLists.txt the path $HOME/picongpu is set as $PICONGPU_ROOT. That environment variable should point towards the relative path of the git-submodule picongpu.

[n01r]

ParaTAXIS also seems to assume that its path is ~/parataxis.

[ax3l]

Looks like no submodules involved. Try running ccmake . in your build dir after configuring.

I found in CMakeLists.txt that you can e.g. set the PIConGPU root to via cmake -DPICONGPU_ROOT=somePath ...

[n01r]

Yeah, sure, I contacted @Flamefire and he said that he forgot to add picongpu as a git-submodule.
He worked with the most recent dev until he left.

[n01r]

Update The default cmakeFlagsNr is set to -1 in configureExample.sh. But the compilation process requires the flag -DPARAM_PRECISION to be set. That would happen if the default were flags[0]. But as we've seen it is -1 and nothing is set.

Thanks @psychocoderHPC for finding this.

[Flamefire]

Actually it was never planned to add submodules as this should at some point be included in PIConGPU. So I used the often used pattern by using a variable _ROOT in the CMakeLists
Even more: This is only a helper. If there is a configured installation of MallocMC then it would be found w/o the picongpu path (

parataxis/CMakeLists.txt

Line 246 in 8d24391

find_package(mallocMC 2.1.0 QUIET)

)
However there was no way to find PMacc through modules so there it is required unless it can be found otherwise (

parataxis/CMakeLists.txt

Line 262 in 8d24391

find_path(PMACC_ROOT_DIR

)

So yes you can either install picongpu to the default location (which I set to be in the home) or point PICONGPU_ROOT to it.

About the flags: I think there was a change so that those defines have to be set instead of defaulting to something. So the default cmakeFlagsNr should be 0 I guess.

[ax3l]

Cool, can you add such information to INSTALL.md or somewhere prominent in the docs?