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Hyperparameter Tuning

About

This feature is in beta.

Gradient provides users the ability to tune hyperparameters for their machine learning models, harnessing the power of our cloud to explore different model configurations and discover an optimal model.

How it works?

Paperspace Hyperparameter Tuning based on Hyperopt

Hyperopt is a method for searching through a hyperparameter space. For example, it can use the Tree-structured Parzen Estimator (TPE) algorithm, which intelligently explores the search space while narrowing down to the best estimated parameters.

It is thus a good method for meta-optimizing a neural network. Whereas a neural network is an optimization problem that is tuned using gradient descent methods, hyperparameters cannot be tuned using gradient descent methods. That's where Hyperopt comes in and shines: it's useful not only for tuning hyperparameters like learning rate, but also for tuning more sophisticated parameters, and in a flexible way: it can change the number of layers of different types; the number of neurons in one layer or another; or even the type of layer to use at a certain place in the network given an array of choices, each themselves with nested, tunable hyperparameters.

This kind of Oriented Random Search is Hyperopt's strength, as opposed to a simpler Grid Search where hyperparameters are pre-established with fixed-step increases. Random Search for Hyperparameter Optimization has proven to be an effective search technique. The paper about this technique sits among the most cited deep learning papers. In summary, it is more efficient to randomly search through values and intelligently narrow the search space, rather than looping on fixed sets of hyperparameter values.

If you want to learn more about Hyperopt, you'll probably want to watch the video below, made by the creator of Hyperopt

How to define Hyperopt parameters

A parameter is defined with either a certain uniform range or a probability distribution, such as:

hp.randint(label, upper)
hp.uniform(label, low, high)
hp.loguniform(label, low, high)
hp.normal(label, mu, sigma)
hp.lognormal(label, mu, sigma)

There are also a few quantized versions of those functions, which round the generated values at each step of "q":

hp.quniform(label, low, high, q)
hp.qloguniform(label, low, high, q)
hp.qnormal(label, mu, sigma, q)
hp.qlognormal(label, mu, sigma, q)

It is also possible to use a "choice" that can lead to hyperparameter nesting:

hp.choice(label, ["list", "of", "potential", "choices"])
hp.choice(label, [hp.uniform(sub_label_1, low, high), hp.normal(sub_label_2, mu, sigma), None, 0, 1, "anything"])

Hyperparameter made easy with Gradient-SDK

hyper_tune()

Function to run hyperparameter tuning.

It accepts the following arguments:

  • train_model User model to tune.

  • hparam_def User definition (scope) of search space. To set this value, refer to hyperopt documentation.

  • algo Search algorithm. Default: tpe.suggest (from hyperopt).

  • max_ecals Maximum number of function evaluations to allow before returning. Default: 25.

  • func Function to be run by hyper tune. Default: fmin (from hyperopt). Do not change this value if you do not know what you are doing!

It returns a dict with information about the tuning process.

It can raise a ConfigError exception with message if there's no connection to MongoDB.

Note: You do not need to worry about setting your MongoDB version; it will be set within Paperspace infrastructure for hyperparameter tuning.

Usage example:

from gradient_sdk import hyper_tune
# Prepare model and search scope
# minimal version
argmin1 = hyper_tune(model, scope)
# pass more arguments
argmin2 = hyper_tune(model, scope, algo=tpe.suggest, max_evals=100)

How to perform Hyperparameter search on Paperspace

Everytime you create a hyperparameter tuning experiment we create at least 3 jobs:

  1. Hyperparameter Server that will run your tuning command

  2. n amount of workers that will run jobs

  3. mongoDb server to store job results

Using the gradient CLI

Assuming that you have configured an API Key for the paperspace cli enter:

gradient hyperparameters run \
--name HyperoptKerasExperimentCLI1 \
--projectId <your-project-id> \
--tuningCommand 'make run_hyperopt' \
--workerContainer tensorflow/tensorflow:1.13.1-gpu-py3 \
--workerMachineType K80 \
--workerCommand 'make run_hyperopt_worker'
--workerCount 2 \
--workspaceUrl git+https://github.com/Paperspace/hyperopt-keras-sample

On successfully creating a hyperparameter experiment it should return something like this:

Hyperparameter created with ID: <experiment_id> and started

For workers and parameter server you can easily access the logs and outputs of the various tasks.

Comparing various runs on Paperspace

This feature is coming soon to our platform!