Minuit2 with openmpi

[radbalint]

Hello,

I am trying to make use of Minuit2 parallelization. I’ve managed to rebuild ROOT with

export USE_OPENMP=1
export USE_PARALLEL_MINUIT2=1

Then I have created my FCN function to minimize and called the line

ROOT::Math::MinimizerOptions::SetDefaultMinimizer("Minuit2");

Then I have compiled the code and set the environment variable

export OMP_NUM_THREADS=8

However, when running my application it always runs on 1 core:

Minuit2Minimizer: Minimize with max-calls 400000 convergence for edm < 0.01 strategy 1
MnSeedGenerator: for initial parameters FCN = 66510892
Info --> MPIProcess::StartMPI: Start MPI on #0 processor
MnSeedGenerator: Initial state:   - FCN =         66510892 Edm =  9.22656e+07 NCalls =   2619
VariableMetric: start iterating until Edm is < 2e-05
....

Maybe I have to set some additional env. variables?

Thanks,
Balint

---

_ROOT Version: 6.10.08
_Platform: Red Hat
_Compiler: g++ 7.3.1

---

[moneta]

Hi,

I presume you are still building ROOT with configure; make and not cmake.
And I also guess you want to use Open MPI and not OpenMP. OpenMPI will run many processes, while OpenMP will run in multi-threads.
For OpenMPI you need to set the env variable USE_MPI and you should be control the number of processors with mpirun

Lorenzo

[radbalint]

Hi Lorenzo,

sorry for my confusing lines. Indeed, I use Open MPI (not OpenMP), so what I did was indeed the following for the building:

export USE_PARALLEL_MINUIT2=1

export USE_MPI=1

but I used cmake, so then I’ll have to probably remake it with configure;make. During the build process

I had to manually go into the minuit folder and give the mpi include path -I/usr/include/openmpi-1.10-x86_64 -pthread -m64

for the g++ build command.

So, indeed previously I did not run it via mpirun. Now after your e-mail running with mpirun -np 8 myprog it does run in multiple processes

and much faster - so I think it works.

Thanks!

Cheers,

Balint