# Manual¶

This manual shows how to use several aspects of auto-sklearn. It either references the examples where possible or explains certain configurations.

## Resampling strategies¶

Examples for using holdout and cross-validation can be found in the example directory of auto-sklearn.

## Parallel computation¶

auto-sklearn supports parallel execution by data sharing on a shared file system. In this mode, the SMAC algorithm shares the training data for it’s model by writing it to disk after every iteration. At the beginning of each iteration, SMAC loads all newly found data points. An example can be found in the example directory.

In it’s default mode, auto-sklearn already uses two cores. The first one is used for model building, the second for building an ensemble every time a new machine learning model has finished training. The file example_sequential .py in the example directory describes how to run these tasks sequentially to use only a single core at a time.

Furthermore, depending on the installation of scikit-learn and numpy, the model building procedure may use up to all cores. Such behaviour is unintended by auto-sklearn and is most likely due to numpy being installed from pypi as a binary wheel (see here). Executing export OPENBLAS_NUM_THREADS=1 should disable such behaviours and make numpy only use a single core at a time.

## Model persistence¶

auto-sklearn is mostly a wrapper around scikit-learn. Therefore, it is possible to follow the persistence example from scikit-learn.