Limit number of threads FFTW uses

ROOT
1

Hi Rooters,

Is there any way to limit the number of threads RooFit uses when performing FFT’s?

On my cluster I’ve got some users using those routines and their jobs rapidly spawn a large number of threads, significantly more than the number of cores on a node. Is there any call they can make in their code to cap the number of threads to the number of cores or need I recompile root/fftw? (If so, which extra flags should I use?)

Thanks in advance,

Paul.

2

Hi Paul,

When performing a likelihood fit in RooFit you can (as user) specify to parallelize likelihood calculations using separate processes when you do fit. In the user code it is specified as pdf.fitTo(data,NumCPU(n)) where n is the number of processes you want. The default (also on multi-core hosts) is 1. This feature is however unrelated to the use of FFTW by RooFit.

Wouter