Metis Tuner on NNI

1. Introduction

Metis offers several benefits over other tuning algorithms. While most tools only predict the optimal configuration, Metis gives you two outputs, a prediction for the optimal configuration and a suggestion for the next trial. No more guess work!

While most tools assume training datasets do not have noisy data, Metis actually tells you if you need to resample a particular hyper-parameter.

While most tools have problems of being exploitation-heavy, Metis’ search strategy balances exploration, exploitation, and (optional) resampling.

Metis belongs to the class of sequential model-based optimization (SMBO) algorithms and it is based on the Bayesian Optimization framework. To model the parameter-vs-performance space, Metis uses both a Gaussian Process and GMM. Since each trial can impose a high time cost, Metis heavily trades inference computations with naive trials. At each iteration, Metis does two tasks:

  • It finds the global optimal point in the Gaussian Process space. This point represents the optimal configuration.

  • It identifies the next hyper-parameter candidate. This is achieved by inferring the potential information gain of exploration, exploitation, and resampling.

Note that the only acceptable types within the search space are quniform, uniform, randint, and numerical choice.

More details can be found in our paper.

2. Usage

classArgs requirements

  • optimize_mode (‘maximize’ or ‘minimize’, optional, default = ‘maximize’) - If ‘maximize’, the tuner will try to maximize metrics. If ‘minimize’, the tuner will try to minimize metrics.

Example Configuration

# config.yml
tuner:
  builtinTunerName: MetisTuner
  classArgs:
    optimize_mode: maximize