ROOT_MAX_THREADS is ignorred when starting root

mvala · December 2, 2025, 7:36am

I am following documentation Multi-threading - ROOT and i would like to use ROOT_MAX_THREADS=22 to do `ROOT::EnableImplicitMT(22);` for me. And it seems to me that it is not working

$ export ROOT_MAX_THREADS=22
$ root
root [0] ROOT::GetThreadPoolSize()
(unsigned int) 0

Thanks for your help

Ciao

Martin

ROOT Version: 6.36.04
Platform: Linux
Compiler: linuxx8664gcc

ferhue · December 2, 2025, 2:26pm

You could try instead with

ROOT::EnableImplicitMT(ROOT::Internal::LogicalCPUBandwidthControl())

mvala · December 3, 2025, 9:44am

I mean that i want to use env variable before i execute root. From root it is working

ferhue · December 3, 2025, 10:06am

export ROOT_MAX_THREADS=22
root
ROOT::EnableImplicitMT(ROOT::Internal::LogicalCPUBandwidthControl())
ROOT::GetThreadPoolSize()

You could even put the first statement in your rootlogon