Warning when using RDataFrame


When I use RDataFrame, or even when I load trees to TChain, I get this warning.

Warning in : Cannot enable implicit multi-threading with 0 threads, please build ROOT with -Dimt=ON

Can someone guide me on how to build Root with -Dimt=ON? Thanks

You are using a version of ROOT that was built without implicit multithreading capabilities. If you are on lxplus, note that this feature is not available by default as described here . You could then use one of the LCG views to pick a version of ROOT with IMT, as suggested in this post.

If you still wish to build ROOT on your own, I advise you to take a look at the guide.

Hi Vincenzo, thanks a lot for the solutions, I will follow the first suggestion! Best regards

One question here. How can i know if the root version has IMT=ON ? All LCG ROOT compilations have IMT=ON ?

root-config --has-imt
root-config --features|grep -i imt