Detector Configuration Files

For advanced use cases, Alibi Detect features powerful configuration file based functionality. As shown below, Drift detectors can be specified with a configuration file named config.toml (adversarial and outlier detectors coming soon!), which can then be passed to {func}~alibi_detect.saving.load_detector:

````{grid-item-card}
:shadow: md
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**Standard instantiation**
^^^

```python
import numpy as np
from alibi_detect.cd import MMDDrift

x_ref = np.load('detector_directory/x_ref.npy')
detector = MMDDrift(x_ref, p_val=0.05)
```
````

````{grid-item-card}
:shadow: md
:margin: 1
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**Config-driven instantiation**
^^^

<p class="codeblock-label">config.toml</p>

```{code-block} toml

name = "MMDDrift"
x_ref = "x_ref.npy"
p_val = 0.05
```

```python
from alibi_detect.saving import load_detector
filepath = 'detector_directory/'
detector = load_detector(filepath)
```
````

Compared to standard instantiation, config-driven instantiation has a number of advantages:

• Human readable: The config.toml files are human-readable (and editable!), providing a readily accessible record of previously created detectors.

• Flexible artefact specification: Artefacts such as datasets and models can be specified as locally serialized objects, or as runtime registered objects (see Specifying complex fields). Multiple detectors can share the same artefacts, and they can be easily swapped.
• Inbuilt validation: The {func}~alibi_detect.saving.load_detector function uses pydantic to validate detector configurations.

To get a general idea of the expected layout of a config file, see the Example config files. Alternatively, to obtain a fully populated config file for reference, users can run one of the example notebooks and generate a config file by passing an instantiated detector to {func}~alibi_detect.saving.save_detector.

Configuration file layout

All detector configuration files follow a consistent layout, simplifying the process of writing simple config files by hand. For example, a {class}~alibi_detect.cd.KSDrift detector with a dill serialized function to preprocess reference and test data can be specified as:

````{tab-item} Config-driven instantiation

<p class="codeblock-label">config.toml</p>

```toml
name = "KSDrift"
x_ref = "x_ref.npy"
p_val = 0.05
preprocess_fn = "function.dill"
```

```python
from alibi_detect.saving import load_detector
detector = load_detector('detector_directory/')
```
````

````{tab-item} Standard instantiation

```python
import numpy as np
from alibi_detect.cd import KSDrift

x_ref = np.load('detector_directory/x_ref.npy')
preprocess_fn = dill.load('detector_directory/function.dill')
detector = MMDDrift(x_ref, p_val=0.05, preprocess_fn=preprocess_fn)
```
````

The name field should always be the name of the detector, for example KSDrift or SpotTheDiffDrift. The remaining fields are the args/kwargs to pass to the detector (see the {mod}alibi_detect.cd docs for a full list of permissible args/kwargs for each detector). All config fields follow this convention, however as discussed in Specifying artefacts, some fields can be more complex than others.

In the  above example `config.toml`, `x_ref` and `preprocess_fn` are stored in `detector_directory/`, but this directory
isn't included in the config file. This is because in the config file, **relative directories are relative to the 
location of the config.toml file**. Filepaths may be absolute, or include nested directories, but **must be POSIX 
paths** i.e. use `/` path separators instead of `\`.

Sometimes, fields representing kwargs need to be set to `None`. However, unspecified fields are set to a detector's 
default kwargs (or for [Artefact dictionaries](dictionaries), the defaults shown in the tables). To set 
fields as `None`, specify them as the string `"None"`. 

(complex_fields)=

Specifying artefacts

When specifying a detector via a config.toml file, the locally stored reference data x_ref must be specified. In addition, many detectors also require (or allow) additional artefacts, such as kernels, functions and models. Depending on their type, artefacts can be specified in config.toml in a number of ways:

• Local files: Simple functions and/or models can be specified as locally stored dill files, whilst data arrays are specified as locally stored numpy npy files.
• Function/object registry: As discussed in Registering artefacts, functions and other objects defined at runtime can be registered using {func}alibi_detect.saving.registry, allowing them to be specified in the config file without having to serialise them. For convenience a number of Alibi Detect functions such as {func}~alibi_detect.cd.tensorflow.preprocess.preprocess_drift are also pre-registered.
• Dictionaries: More complex artefacts are specified via nested dictionaries, usually containing a src field and additional option/setting fields. Sometimes these fields may be nested artefact dictionaries themselves. See Artefact dictionaries for further details.

The following table shows the allowable formats for all possible config file artefacts.

:name: all-artefacts-table

|Field                     |.npy file  |.dill file  |[Registry](registering_artefacts)|[Artefact Dictionary](dictionaries)                                                                         | 
|:-------------------------|:---------:|:----------:|:-------------------------------:|:----------------------------------------------------------------------------------------------------------:|
|`x_ref`                   |✔          |            |                                 |                                                                                                            |
|`c_ref`                   |✔          |            |                                 |                                                                                                            |
|`reg_loss_fn`             |           |✔           |✔                                |                                                                                                            |
|`dataset`                 |           |✔           |✔                                |                                                                                                            |
|`initial_diffs`           |✔          |            |                                 |                                                                                                            |
|`model`/`proj`            |           |            |✔                                |{class}`~alibi_detect.saving.schemas.ModelConfig`                                                           |
|`preprocess_fn`           |           |✔           |✔                                |{class}`~alibi_detect.saving.schemas.PreprocessConfig`                                                      |
|`preprocess_batch_fn`     |           |✔           |✔                                |                                                                                                            |
|`embedding`               |           |            |✔                                |{class}`~alibi_detect.saving.schemas.EmbeddingConfig`                                                       |
|`tokenizer`               |           |            |✔                                |{class}`~alibi_detect.saving.schemas.TokenizerConfig`                                                       |
|`kernel`                  |           |            |✔                                |{class}`~alibi_detect.saving.schemas.KernelConfig` or {class}`~alibi_detect.saving.schemas.DeepKernelConfig`|
|`kernel_a`/`kernel_b`     |           |            |✔                                |{class}`~alibi_detect.saving.schemas.KernelConfig`                                                          |
|`optimizer`               |           |✔           |✔                                | {class}`~alibi_detect.saving.schemas.OptimizerConfig`                                                      |

(dictionaries)=

Artefact dictionaries

Simple artefacts, for example a simple preprocessing function serialized in a dill file, can be specified directly: preprocess_fn = "function.dill". However, if more complex, they can be specified as an artefact dictionary:

config.toml (excerpt)

[preprocess_fn]
src = "function.dill"
kwargs = {'kwarg1'=42, 'kwarg2'=false}

Here, the preprocess_fn field is a {class}~alibi_detect.saving.schemas.PreprocessConfig artefact dictionary. In this example, specifying the preprocess_fn function as a dictionary allows us to specify additional kwarg's to be passed to the function upon loading. This example also demonstrates the flexibility of the TOML format, with dictionaries able to be specified with {} brackets or by sections demarcated with [] brackets (see the TOML documentation for more details on the TOML format).

Other config fields in the {ref}all-artefacts-table table can be specified via artefact dictionaries in a similar way. For example, the model and proj fields can be set as TensorFlow or PyTorch models via the {class}~alibi_detect.saving.schemas.ModelConfig dictionary. Often an artefact dictionary may itself contain nested artefact dictionaries, as is the case in in the following example, where a preprocess_fn is specified with a TensorFlow model.

config.toml (excerpt)

[preprocess_fn]
src = "@cd.tensorflow.preprocess.preprocess_drift"
batch_size = 32

[preprocess_fn.model]
src = "model/"

Each artefact dictionary has an associated pydantic model which is used for validation of config files. The documentation for these pydantic models provides a description of the permissible fields for each artefact dictionary. For examples of how the artefact dictionaries can be used in practice, see {ref}examples.

(registering_artefacts)=

Registering artefacts

Custom artefacts defined in Python code may be specified in the config file without the need to serialise them, by first adding them to the Alibi Detect artefact registry using the {mod}alibi_detect.saving.registry submodule. This submodule harnesses the catalogue library to allow functions to be registered with a decorator syntax:

````{grid-item-card}
:shadow: md
:margin: 1
:padding: 1
:columns: auto

**Registering a function**
^^^

```python
import numpy as np
from alibi_detect.saving import registry, load_detector

# Register a simple function
@registry.register('my_function.v1')
def my_function(x: np.ndarray) -> np.ndarray:
    "A custom function to normalise input data."
    return (x - x.mean()) / x.std()

# Load detector with config.toml file referencing "@my_function.v1"    
detector = load_detector(filepath)
```
````

````{grid-item-card}
:shadow: md
:margin: 1
:padding: 1
:columns: auto

**Specifying in a config.toml**
^^^

<p class="codeblock-label">config.toml</p>

```toml
name = "MMDDrift"
x_ref = "x_ref.npy"
preprocess_fn = "@my_function.v1"
```
````

Once the custom function has been registered, it can be specified in config.toml files via its reference string (with @ prepended), for example "@my_function.v1" in this case. Other objects, such as custom tensorflow or pytorch models, can also be registered by using the register function directly. For example, to register a tensorflow encoder model:

import tensorflow as tf
from tensorflow.keras.layers import Conv2D, Dense, Flatten, InputLayer
from alibi_detect.saving import registry

encoder_net = tf.keras.Sequential(
  [
      InputLayer(input_shape=(32, 32, 3)),
      Conv2D(64, 4, strides=2, padding='same', activation=tf.nn.relu),
      Conv2D(128, 4, strides=2, padding='same', activation=tf.nn.relu),
      Flatten(),
      Dense(32,)
  ]
)
registry.register("my_encoder.v1", func=encoder_net)

Examining registered artefacts

A registered object's metadata can be obtained with registry.find(), and all currently registered objects can be listed with registry.get_all(). For example, registry.find("my_function.v1") returns the following:

{'module': '__main__', 'file': 'test.py', 'line_no': 3, 'docstring': 'A custom function to normalise input data.'}

Pre-registered utility functions/objects

For convenience, Alibi Detect also pre-registers a number of commonly used utility functions and objects.

Function/Class	Registry reference*	Tensorflow	Pytorch
{func}~alibi_detect.cd.tensorflow.preprocess.preprocess_drift	'@cd.[backend].preprocess.preprocess_drift'	✔	✔
{class}~alibi_detect.utils.tensorflow.kernels.GaussianRBF	'@utils.[backend].kernels.GaussianRBF'	✔	✔
{class}~alibi_detect.utils.tensorflow.data.TFDataset	'@utils.tensorflow.data.TFDataset'	✔

*For backend-specific functions/classes, [backend] should be replaced the desired backend e.g. tensorflow or pytorch.

These can be used in config.toml files. Of particular importance are the preprocess_drift utility functions, which allows models, tokenizers and embeddings to be easily specified for preprocessing, as demonstrated in the IMDB example.

(examples)=

Example config files

% To demonstrate the config-driven functionality, example detector configurations are presented in this section.

% To download a config file and its related artefacts, click on the Run Me tabs, copy the Python code, and run it % in your local Python shell.

(imdb_example)=

Drift detection on text data

This example presents a configuration for the {class}~alibi_detect.cd.MMDDrift detector used in Text drift detection on IMDB movie reviews. The detector will pass the input text data through a preprocess_fn step consisting of a tokenizer, embedding and model. An Untrained AutoEncoder (UAE) model is included in order to reduce the dimensionality of the embedding space, which consists of a 768-dimensional vector for each instance.

%````{tabbed} Config file %:new-group:

config.toml

x_ref = "x_ref.npy"
name = "MMDDrift"

[preprocess_fn]
src = "@cd.tensorflow.preprocess.preprocess_drift"
batch_size = 32
max_len = 100
tokenizer.src = "tokenizer/"

[preprocess_fn.model]
src = "model/"

[preprocess_fn.embedding]
src = "embedding/"
type = "hidden_state"
layers = [-1, -2, -3, -4, -5, -6, -7, -8]

% % %{tabbed} Run Me % %python %from alibi_detect.utils.fetching import fetch_config %from alibi_detect.saving import load_detector %filepath = 'IMDB_example_MMD/' %fetch_config('imdb_mmd', filepath) %detector = load_detector(filepath) % %````

% TODO: Add a second example demo-ing loading of state (once implemented). e.g. for online or learned kernel.

%## Advanced usage

(validation)=

Validating config files

When {func}~alibi_detect.saving.load_detector is called, the {func}~alibi_detect.saving.validate_config utility function is used internally to validate the given detector configuration. This allows any problems with the configuration to be detected prior to sometimes time-consuming operations of loading artefacts and instantiating the detector. {func}~alibi_detect.saving.validate_config can also be used by devs working with Alibi Detect config dictionaries.

Under-the-hood, {func}~alibi_detect.saving.load_detector parses the config.toml file into a unresolved config dictionary. It then passes this dict through {func}~alibi_detect.saving.validate_config, to check for errors such as incorrectly named fields, and incorrect types. If working directly with config dictionaries, the same process can be done explicitly, for example:

from alibi_detect.saving import validate_config

# Define a simple config dict
cfg = {
    'name': 'MMDDrift',
    'x_ref': 'x_ref.npy',
    'p_val': [0.05],
    'bad_field': 'oops!'
}

# Validate the config
validate_config(cfg)

This will return a ValidationError because p_val is expected to be float not a list, and bad_field isn't a recognised field for the MMDDrift detector:

ValidationError: 2 validation errors for MMDDriftConfig
p_val
  value is not a valid float (type=type_error.float)
bad_field
  extra fields not permitted (type=value_error.extra)

Validating at this stage is useful as errors can be caught before the sometimes time-consuming operation of resolving the config dictionary, which involves loading each artefact in the dictionary ({func}~alibi_detect.saving.read_config and {func}~alibi_detect.saving.resolve_config can be used to manually read and resolve a config for debugging). The resolved config dictionary is then also passed through {func}~alibi_detect.saving.validate_config, and this second validation can also be done explicitly:

import numpy as np
from alibi_detect.saving import validate_config

# Create some reference data
x_ref = np.random.normal(size=(100,5))

# Define a simple config dict
cfg = {
    'name': 'MMDDrift',
    'x_ref': x_ref,
    'p_val': 0.05
}

# Validate the config
validate_config(cfg, resolved=True)

Note that since resolved=True, {func}~alibi_detect.saving.validate_config is now expecting x_ref to be a Numpy ndarray instead of a string. This second level of validation can be useful as it helps detect problems with loaded artefacts before attempting the sometimes time-consuming operation of instantiating the detector.

%### Detector specification schemas % %Validation of detector config files is performed with pydantic. Each %detector's unresolved configuration is represented by a pydantic model, stored in DETECTOR_CONFIGS. Information on %a detector config's permitted fields and their types can be obtained via the config model's schema method %(or schema_json if a json formatted string is preferred). For example, for the KSDrift detector: % %python %from alibi_detect.saving.schemas import DETECTOR_CONFIGS %schema = DETECTOR_CONFIGS['KSDrift'].schema() % % % %returns a dictionary with the keys ['title', 'type', 'properties', 'required', 'additionalProperties', 'definitions']. %The 'properties' item is a dictionary containing all the possible fields for the detector: % %python %{'name': {'title': 'Name', 'type': 'string'}, % 'version': {'title': 'Version', 'default': '0.8.1dev', 'type': 'string'}, % 'backend': {'title': 'Backend', % 'default': 'tensorflow', % 'enum': ['tensorflow', 'pytorch'], % 'type': 'string'}, % 'x_ref': {'title': 'X Ref', 'default': 'x_ref.npy', 'type': 'string'}, % 'p_val': {'title': 'P Val', 'default': 0.05, 'type': 'number'}, % 'x_ref_preprocessed': {'title': 'X Ref Preprocessed', % 'default': False, % 'type': 'boolean'}, % ... % } % % %Compulsory fields are listed in 'required', whilst additional pydantic model definitions such as %ModelConfig are stored in 'definitions'. These additional models define the schemas for the %artefact dictionaries. % %Similarly, resolved detector configurations are represented by pydantic models stored in %DETECTOR_CONFIGS_RESOLVED. The difference being that for these models, artefacts are expected to have their %resolved types, for example x_ref should be a NumPy ndarray. The schema and schema_json methods can be applied %to these models in the same way.