Conda environment for building

ROOT
,
1

Is there a conda environment in which I can build root? I tried to create one myself with

mamba create -n buildroot make=4.4 cmake=3.31 gxx=15.2 gcc=15.2 python=3.13 liblzma-devel xorg-libx11 xorg-libxpm xorg-libxft xorg-libxext xorg-xorgproto expat xrootd

and then build root with
cmake -DCMAKE_INSTALL_PREFIX=../root_install -DCMAKE_CXX_STANDARD=17 -DCMAKE_PREFIX_PATH=$CONDA_PREFIX -DCMAKE_FIND_ROOT_PATH=$CONDA_PREFIX -DCMAKE_FIND_ROOT_PATH_MODE_PACKAGE=ONLY -DCMAKE_FIND_ROOT_PATH_MODE_LIBRARY=ONLY -DCMAKE_FIND_ROOT_PATH_MODE_INCLUDE=ONLY ../root_src

and

cmake --build . -- install -j10

I get
[ 65%] Building CXX object net/rpdutils/CMakeFiles/SrvAuth.dir/src/rpdutils.cxx.o <<< cling interactive line includer >>>: remark: building module 'Net' as '[…]/lib/Net.pcm' [-Rmodule-build] Error: Building module 'Net' implicitly. If 'Net' requires a dictionary please specify build dependency: 'G__MultiProc.cxx' depends on 'Net'. Otherwise, specify '-mByproduct Net' to disable this diagnostic.

In a docker container I can of course build it, but it would be nice to build it outside in a conda environment for better performance

ROOT Version: latest stable branch
Platform: Fedora
Compiler: gcc 15.2

2

Maybe @vpadulan can give some hints, but first of all, why don’t you use the pre-built version of ROOT in Conda?

3

I am fixing a bug I found

4

OK, then I don’t know if it’s the best alternative. Anyway, let’s see if @vpadulan has an idea

1 Like
5

Dear @KoljaFrahm ,

Thanks for reaching out to the forum! I have to say I’ve never tried this myself, and for all intents and purposes I would say we cannot offer any practical support on this at the moment. I will still try to give ideas and suggestions though.

I would start by at the very least creating a conda environment that has all the dependencies we list in our recipe at root-feedstock/recipe/recipe.yaml at 9f5368f9a08d5744667524dcaf849e197312d77a · conda-forge/root-feedstock · GitHub . You need to make an intersection between build, host and run for what makes sense for your target platform.

Then, looking at your cmake command, I’m actually not sure why you’re passing all those CMAKE_* options, I don’t know how many of those are actually necessary, some might even be playing against you.

but it would be nice to build it outside in a conda environment for better performance

I don’t understand where this notion comes from, given the same hardware, why should the conda environment be more performant?

Cheers,

Vincenzo

2 Likes
6

This seems to work. I will formulate later a longer reply, but I just don’t want this topic to close right now

7

Dear @KoljaFrahm ,

Great to know that you made progress! If you find time, it would be great to document this somewhere for other users who may want to do the same, thanks!

Cheers,

Vincenzo

8

I now had time to test it a bit more.
I created a mamba environment as you said, with the intersection between build, host and run
The file for the environment can be found here (not too sure about the headings):

and you can create the environment with

mamba env create root-feedstock.yaml

Then root compiles. I actually used
cmake -DCMAKE_INSTALL_PREFIX=../install -DCMAKE_CXX_STANDARD=20 ../root-src

but I think other versions should also work.

I used them before so cmake can only see the conda libraries but it works now without.

The main advantage is that it is now much easier to cache the building process. Before, root had to build anew if something small changed in the source code. I guess the docker performance compared to just running it without a docker container is not too much, but I feel like I have better control over it now.

1 Like
9

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