Using Kur for Real

Let’s get started using Kur! There’s two topics we need to cover: describing models in a specification file, and actually running Kur.


If you haven’t already, make sure you work through the Examples: In Depth first. Otherwise, this might feel a little overwhelming, and Kur shouldn’t make you feel like that.

Running Kur

Kur is pretty easy to run. It looks like this:

# usage:
kur [-v] {train | test | evaluate | build | dump | data} KURFILE.yml
# train the Kur MNIST example
kur train speech.yml

# test the Kur speech example while showing debug output
kur -vv test speech.yml

You feed Kur a Kurfile, and tell it what to do with the file (e.g. kur train mnist.yml, which is the first example in Examples: In Depth ). Train, test, and evaluate will be explained in detail in the next section on Kurfile specification. The other commands are:

  • build is kind of like train, but does not load the data set, and doesn’t actually start training. Instead, build just assembles the model. This is useful for debugging the construction of models, looking for obvious problems, while not bothering with loading and training on data just yet.
  • dump displays a JSON representation of the parsed Kurfile. It doesn’t do anything else, and is primarily useful as a debugging tool to see what information Kur is using. If you are using complicated Jinja2 syntax, including multiple Kurfiles, or want to verify YAML anchors, then this is an invaluable debugging command.
  • data will _not_ train/test/evaluate a model, but it will do _almost_ everything else. Instead of actually using the model, it will instead print out the data that it _would_ have fed into the very first batch. This is useful for checking that data is flowing in the way you expect through Kur.

Note: Keep in mind the optional flags -v and -vv. If you are curious about the lower-level details of what Kur is doing (like the nuts and bolts of how the network is being buit), then feel free to add -v to enable INFO-level output, or even -vv to enable DEBUG-level ouput (there’s a lot).

By default, Kur tries not to be overly verbose in terminal output, so it only prints progress indicators, warnings and errors to the console while running. You should definitely pay attention to any warnings or errors: they are indicative of something unexpected or wrong. If Kur seems “stuck,” try enabling verbose output to see what it is up to.


One other tip: the train/test/evaluate commands can all take a --step flag. This sets a “breakpoint” just before data is given to the model at each batch, requiring you to press ENTER to continue. Moreover, if DEBUG-level output is enabled (-vv), then the entire batch of data will be printed to the screen, and the model predictions will be printed immediately after the batch is processed. This is primarily useful to Kur developers who want to inspect the data that is being passed into the model.

Kurfile Template & Info

Kur uses Kurfiles. These are “specification” files which describe the model, hyperparameters, data sets, training/evaluation options, and functional settings. This doc gives a quick, whirlwind tour of how Kur interprets the specification files. Kurfiles can be written in YAML or JSON.

For more details, see Kurfile Specification.

YAML Notes

Since YAML is the default supported Kur format, here are a couple pointers.

  • YAML documents need to start with three dashes: ---. Everything you add to the file should go below those dashes.
  • Documents can be explicitly terminated by three periods: ..., but this is optional.
  • YAML is a “whitespace matters” language. You should never use tabs in YAML.
  • YAML files should use the .yaml or .yml extension.
  • YAML comments start with the hash character: #

For details of the YAML syntax, take a look at the Ansible overview

Skeleton Outline of a Simple Kurfile

This is a simplied template you can use for writing Kur models.


# Other kurfiles to load (optional)

# Global variables go here (optional)

# Your core model goes here (required)

  # Input data
  - input: INPUT

  # ... other layers ...

  # Last layer. Change "softmax" if it is appropriate.
  - activation: softmax
    name: OUTPUT

# All the information you need for training.

  # Where to get training data from.
  # NOTE: `TRAIN_DATA` needs to have dictionary keys named `INPUT` and
  #       `OUTPUT`, corresponding to the `INPUT` and `OUTPUT` names in the
  #       model section above.
    - pickle: TRAIN_DATA

  # Try playing with the batch size and watching accuracy and speed.
    batch_size: 32

  # How many epochs to train for.
  epochs: 10

  # Where to load and save weights.
    initial: INITIAL_WEIGHTS

  # The optimizer to use. Try doubling or halving the learning rate.
    name: adam
    learning_rate: 0.001

# You need this section if you want to run validation checks during
# training.
    - pickle: VALIDATION_DATA

  # Where to save the best validation weights.

# You need this section only if you want to run standalone test runs to
# calculate loss.
    - pickle: TEST_DATA
  # Which weights to use for testing.

# This section is for trying out your model on new data.
  # The data to supply as input. Unlike the train/validate/test sections,
  # you do not need a corresponding `OUTPUT` key. But if you do supply one,
  # Kur can save it to the output file for you so it's easy to use during
  # post-processing
    - pickle: NEW_DATA

  # Which weights to use for evaluation.

  # Where to save the result (as a Python pickle)
  destination: RESULTS.pkl

# Required for training, validation and testing
  # You need an entry whose target is `OUTPUT` from the model section above.
  - target: OUTPUT

    # The name of the loss function. Change it if appropriate
    name: categorical_crossentropy

We’re going to cover the simplest details of these sections.

  • include: You only need this if you’ve split your specification into multiple files. Otherwise, you can leave it empty or just remove it.

  • settings: This is the place that you can set global variables that you want to reference using the templating engine later (e.g., data sets or model hyperparameters). If you don’t have any variables, you can just leave this section empty or remote it.

  • model: This is the fun part! Make sure you have an input entry, and a give the final layer a name, too (it’s your output). The names need to correspond to the data that gets loaded during training, evaluation, etc. For a full list of “containers” (that’s what Kur calls each entry in the model section), see Containers: Layers & Operators. The Examples: In Depth are also a good place to start.

  • train: Everything you want to tell Kur about the desired training process.

    • The data section just tells Kur to load a pickled Python file called TRAIN_DATA. That file should be a Python dictionary with keys corresponding to the input/output names you chose in the model section. The values in that dictionary should be numpy arrays that you want to feed into the Kur model.
    • The batch_size can be used to change how many training samples Kur uses at each step in the training process.
    • epochs tells Kur how many iterations of the entire training set it should run through before stopping.
    • The weights section tells Kur where it should save the state of the model (the model weights or parameters). This section tells Kur to load any existing weights from the initial file; these weights might exist because you’ve already trained the model a few times and now you want to train some more, picking up where you left off. If this initial file doesn’t exist, Kur just assumes it’s your first time through the training process and chugs along merrily. The best file tells Kur where to save the weights if they produce the lowest loss (with respect to the training data) that Kur has seen yet. The last file is where Kur saves the weights before it stops training.
    • The optimizer is where you tell Kur which algorithm it should use to try and improve the model performance / minimize loss.
  • validate: It’s usually a good idea to have a validation set that you can use to independently assess how the model is performing. This is the place for it! It accepts a data section just like train, and the weights tell Kur where to save the weights whenever they produce the lowest historical loss with respect to the validation data.

  • test: If you have a test set, put its data specification here. The weights field tells Kur which weights you want it to load first.

  • evaluate: This is where you put information about new data sets you want to apply your model to. And you guessed it—the data section is just like all the others. The difference is that the pickled data dictionary not longer required a key corresponding to the model output from the model section; but if you give Kur the true output data anyway, it can use it for additional statistics and save it to the output for for you. The weights field tells Kur which weights to load before evaluating. destination names the output file where Kur should save the model results. It will save them as a Python pickle.

  • loss: Every model output needs a corresponding loss function. Make sure you have a target for each model output (it should have the same name, too, just like the data files).