# Source code for getml.feature_learning.multirel

```
# Copyright 2022 The SQLNet Company GmbH
#
# This file is licensed under the Elastic License 2.0 (ELv2).
# Refer to the LICENSE.txt file in the root of the repository
# for details.
#
"""
Feature learning based on Multi-Relational Decision Tree Learning.
"""
from dataclasses import dataclass, field
from typing import Any, ClassVar, Dict, List, Optional, Union
from .aggregations import _Aggregations
from .aggregations import multirel as multirel_aggregations
from .fastprop import FastProp
from .feature_learner import _FeatureLearner
from .validation import _validate_multirel_parameters
# --------------------------------------------------------------------
[docs]@dataclass(repr=False)
class Multirel(_FeatureLearner):
"""
Feature learning based on Multi-Relational Decision Tree Learning.
:class:`~getml.feature_learning.Multirel` automates feature learning
for relational data and time series. It is based on an efficient
variation of the Multi-Relational Decision Tree Learning (MRDTL).
For more information on the underlying feature learning algorithm, check
out the :ref:`User guide <feature_learning_algorithms_multirel>`.
Args:
aggregation (List[:class:`~getml.feature_learning.aggregations`], optional):
Mathematical operations used by the automated feature
learning algorithm to create new features.
Must be from :mod:`~getml.feature_learning.aggregations`.
allow_sets (bool, optional):
Multirel can summarize different categories into sets for
producing conditions. When expressed as SQL statements these
sets might look like this:
.. code-block:: sql
t2.category IN ( 'value_1', 'value_2', ... )
This can be very powerful, but it can also produce
features that are hard to read and might be prone to
overfitting when the `sampling_factor` is too low.
delta_t (float, optional):
Frequency with which lag variables will be explored in a
time series setting. When set to 0.0, there will be no lag
variables.
For more information please refer to
:ref:`data_model_time_series`. Range: [0, :math:`\\infty`]
grid_factor (float, optional):
Multirel will try a grid of critical values for your
numerical features. A higher `grid_factor` will lead to a
larger number of critical values being considered. This
can increase the training time, but also lead to more
accurate features. Range: (0, :math:`\\infty`]
loss_function (:class:`~getml.feature_learning.loss_functions`, optional):
Objective function used by the feature learning algorithm
to optimize your features. For regression problems use
:class:`~getml.feature_learning.loss_functions.SquareLoss` and for
classification problems use
:class:`~getml.feature_learning.loss_functions.CrossEntropyLoss`.
max_length (int, optional):
The maximum length a subcondition might have. Multirel
will create conditions in the form
.. code-block:: sql
(condition 1.1 AND condition 1.2 AND condition 1.3 )
OR ( condition 2.1 AND condition 2.2 AND condition 2.3 )
...
Using this parameter you can set the maximum number of
conditions allowed in the brackets. Range: [0, :math:`\\infty`]
min_df (int, optional):
Only relevant for columns with role :const:`~getml.data.roles.text`.
The minimum
number of fields (i.e. rows) in :const:`~getml.data.roles.text` column a
given word is required to appear in to be included in the bag of words.
Range: [1, :math:`\\infty`]
min_num_samples (int, optional):
Determines the minimum number of samples a subcondition
should apply to in order for it to be considered. Higher
values lead to less complex statements and less danger of
overfitting. Range: [1, :math:`\\infty`]
num_features (int, optional):
Number of features generated by the feature learning
algorithm. Range: [1, :math:`\\infty`]
num_subfeatures (int, optional):
The number of subfeatures you would like to extract in a
subensemble (for snowflake data model only). See
:ref:`data_model_snowflake_schema` for more
information. Range: [1, :math:`\\infty`]
num_threads (int, optional):
Number of threads used by the feature learning algorithm. If set to
zero or a negative value, the number of threads will be
determined automatically by the getML engine. Range:
[:math:`0`, :math:`\\infty`]
propositionalization (:class:`~getml.feature_learning.FastProp`, optional):
The feature learner used for joins which are flagged to be
propositionalized (by setting a join's `relationship` parameter to
:const:`getml.data.relationship.propositionalization`)
regularization (float, optional):
Most important regularization parameter for the quality of
the features produced by Multirel. Higher values will lead
to less complex features and less danger of overfitting. A
`regularization` of 1.0 is very strong and allows no
conditions. Range: [0, 1]
round_robin (bool, optional):
If True, the Multirel picks a different `aggregation`
every time a new feature is generated.
sampling_factor (float, optional):
Multirel uses a bootstrapping procedure (sampling with
replacement) to train each of the features. The sampling
factor is proportional to the share of the samples
randomly drawn from the population table every time
Multirel generates a new feature. A lower sampling factor
(but still greater than 0.0), will lead to less danger of
overfitting, less complex statements and faster
training. When set to 1.0, roughly 20,000 samples are drawn
from the population table. If the population table
contains less than 20,000 samples, it will use standard
bagging. When set to 0.0, there will be no sampling at
all. Range: [0, :math:`\\infty`]
seed (Union[int,None], optional):
Seed used for the random number generator that underlies
the sampling procedure to make the calculation
reproducible. Internally, a `seed` of None will be mapped to
5543. Range: [0, :math:`\\infty`]
share_aggregations (float, optional):
Every time a new feature is generated, the `aggregation`
will be taken from a random subsample of possible
aggregations and values to be aggregated. This parameter
determines the size of that subsample. Only relevant when
`round_robin` is False. Range: [0, 1]
share_conditions (float, optional):
Every time a new column is tested for applying conditions,
it might be skipped at random. This parameter determines
the probability that a column will *not* be
skipped. Range: [0, 1]
shrinkage (float, optional):
Since Multirel works using a gradient-boosting-like
algorithm, `shrinkage` (or learning rate) scales down the
weights and thus the impact of each new tree. This gives
more room for future ones to improve the overall
performance of the model in this greedy algorithm. Higher
values will lead to more danger of overfitting. Range: [0,
1]
silent (bool, optional):
Controls the logging during training.
vocab_size (int, optional):
Determines the maximum number
of words that are extracted in total from :const:`getml.data.roles.text`
columns. This can be interpreted as the maximum size of the bag of words.
Range: [0, :math:`\\infty`]
Note:
Not supported in the getML community edition.
"""
# ----------------------------------------------------------------
agg_sets: ClassVar[_Aggregations] = multirel_aggregations
# ----------------------------------------------------------------
aggregation: List[str] = field(
default_factory=lambda: multirel_aggregations.Default
)
allow_sets: bool = True
delta_t: float = 0.0
grid_factor: float = 1.0
loss_function: Optional[str] = None
max_length: int = 4
min_df: int = 30
min_num_samples: int = 1
num_features: int = 100
num_subfeatures: int = 5
num_threads: int = 0
propositionalization: FastProp = field(default_factory=FastProp)
regularization: float = 0.01
round_robin: bool = False
sampling_factor: float = 1.0
seed: int = 5543
share_aggregations: float = 0.0
share_conditions: float = 1.0
shrinkage: float = 0.0
silent: bool = True
vocab_size: int = 500
# ----------------------------------------------------------------
[docs] def validate(self, params: Optional[Dict[str, Any]] = None) -> None:
"""
Checks both the types and the values of all instance
variables and raises an exception if something is off.
Args:
params (dict, optional): A dictionary containing
the parameters to validate. If not is passed,
the own parameters will be validated.
"""
# ------------------------------------------------------------
if params is None:
params = self.__dict__
else:
params = {**self.__dict__, **params}
# ------------------------------------------------------------
if not isinstance(params, dict):
raise ValueError("params must be None or a dictionary!")
# ------------------------------------------------------------
for kkey in params:
if kkey not in type(self)._supported_params:
raise KeyError(
f"Instance variable '{kkey}' is not supported in {self.type}."
)
# ------------------------------------------------------------
_validate_multirel_parameters(**params)
# --------------------------------------------------------------------
```