Parallelization

The model fitting as well as the forecasting offer the possibility of parallelization. Out of the box both tasks are parallelized by scikit-hts. However, the overhead introduced with the parallelization should not be underestimated. Here we discuss the different settings to control the parallelization. To achieve best results for your use-case you should experiment with the parameters.

Parallelization of Model Fitting

We use a multiprocessing.Pool to parallelize the fitting of each model to a node’s data. On instantiation we set the Pool’s number of worker processes to n_jobs. This field defaults to the number of processors on the current system. We recommend setting it to the maximum number of available (and otherwise idle) processors.

The chunksize of the Pool’s map function is another important parameter to consider. It can be set via the chunksize field. By default it is up to multiprocessing.Pool is parallelisation parameter. One data chunk is defined as a singular time series for one node. The chunksize is the number of chunks that are submitted as one task to one worker process. If you set the chunksize to 10, then it means that one worker task corresponds to calculate all forecasts for 10 node time series. If it is set it to None, depending on distributor, heuristics are used to find the optimal chunksize. The chunksize can have an crucial influence on the optimal cluster performance and should be optimised in benchmarks for the problem at hand.

Parallelization of Forecasting

For the feature extraction scikit-hts exposes the parameters n_jobs and chunksize. Both behave analogue to the parameters for the feature selection.

To do performance studies and profiling, it sometimes quite useful to turn off parallelization at all. This can be setting the parameter n_jobs to 0.

Acknowledgement

This documentation, as well as the underlying implementation, exists only thanks to the folks at blue-yonder. The This page was pretty much copy and pasted from their tsfresh package. Many thanks for their excellent package.