Limit number of threads FFTW uses

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,


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.