# CIFAR-10 examples¶

## Overview¶

CIFAR-10 classification is a common benchmark problem in machine learning. The CIFAR-10 dataset is the collection of images. It is one of the most widely used datasets for machine learning research which contains 60,000 32x32 color images in 10 different classes. Thus, we use CIFAR-10 classification as an example to introduce NNI usage.

### Goals¶

As we all know, the choice of model optimizer is directly affects the performance of the final metrics. The goal of this tutorial is to tune a better performace optimizer to train a relatively small convolutional neural network (CNN) for recognizing images.

In this example, we have selected the following common deep learning optimizer:

### Experimental¶

#### Preparations¶

This example requires PyTorch. PyTorch install package should be chosen based on python version and cuda version.

Here is an example of the environment python==3.5 and cuda == 8.0, then using the following commands to install PyTorch:

python3 -m pip install http://download.pytorch.org/whl/cu80/torch-0.4.1-cp35-cp35m-linux_x86_64.whl
python3 -m pip install torchvision


#### CIFAR-10 with NNI¶

Search Space

As we stated in the target, we target to find out the best optimizer for training CIFAR-10 classification. When using different optimizers, we also need to adjust learning rates and network structure accordingly. so we chose these three parameters as hyperparameters and write the following search space.

{
"lr":{"_type":"choice", "_value":[0.1, 0.01, 0.001, 0.0001]},
"model":{"_type":"choice", "_value":["vgg", "resnet18", "googlenet", "densenet121", "mobilenet", "dpn92", "senet18"]}
}


Implemented code directory: search_space.json

Trial

The code for CNN training of each hyperparameters set, paying particular attention to the following points are specific for NNI:

• Use nni.get_next_parameter() to get next training hyperparameter set.
• Use nni.report_intermediate_result(acc) to report the intermedian result after finish each epoch.
• Use nni.report_final_result(acc) to report the final result before the trial end.

Implemented code directory: main.py

You can also use your previous code directly, refer to How to define a trial for modify.

Config

Here is the example of running this experiment on local(with multiple GPUs):

code directory: examples/trials/cifar10_pytorch/config.yml

Here is the example of running this experiment on OpenPAI:

code directory: examples/trials/cifar10_pytorch/config_pai.yml

The complete examples we have implemented: examples/trials/cifar10_pytorch/

#### Launch the experiment¶

We are ready for the experiment, let’s now run the config.yml file from your command line to start the experiment.

nnictl create --config nni/examples/trials/cifar10_pytorch/config.yml