learned_optimizer

Learned Optimizer

Code for Learned Optimizers that Scale and Generalize.

Requirements

• Bazel (install)
• TensorFlow >= v1.3
• Python 2.7.x

Training a Learned Optimizer

Code Overview

In the top-level directory, metaopt.py contains the code to train and test a learned optimizer. metarun.py packages the actual training procedure into a single file, defining and exposing many flags to tune the procedure, from selecting the optimizer type and problem set to more fine-grained hyperparameter settings. There is no testing binary; testing can be done ad-hoc via metaopt.test_optimizer by passing an optimizer object and a directory with a checkpoint.

The optimizer directory contains a base trainable_optimizer.py class and a number of extensions, including the hierarchical_rnn optimizer used in the paper, a coordinatewise_rnn optimizer that more closely matches previous work, and a number of simpler optimizers to demonstrate the basic mechanics of a learnable optimizer.

The problems directory contains the code to build the problems that were used in the meta-training set.

Binaries

metarun.py: meta-training of a learned optimizer

Command-Line Flags

The flags most relevant to meta-training are defined in metarun.py. The default values will meta-train a HierarchicalRNN optimizer with the hyperparameter settings used in the paper.

Using a Learned Optimizer as a Black Box

The trainable_optimizer inherits from tf.train.Optimizer, so a properly instantiated version can be used to train any model in any APIs that accept this class. There are just 2 caveats:

1. If using the Hierarchical RNN optimizer, the apply_gradients return type must be changed (see comments inline for what exactly must be removed)

2. Care must be taken to restore the variables from the optimizer without overriding them. Optimizer variables should be loaded manually using a pretrained checkpoint and a tf.train.Saver with only the optimizer variables. Then, when constructing the session, ensure that any automatic variable initialization does not re-initialize the loaded optimizer variables.

Contact for Issues

• Olga Wichrowska (@olganw), Niru Maheswaranathan (@nirum)