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from __future__ import unicode_literals
import json
import logging
from builtins import str, zip
from pathlib import Path
from snips_inference_agl.common.log_utils import DifferedLoggingMessage
from snips_inference_agl.common.utils import (fitted_required)
from snips_inference_agl.constants import RES_PROBA
from snips_inference_agl.exceptions import LoadingError
from snips_inference_agl.intent_classifier.featurizer import Featurizer
from snips_inference_agl.intent_classifier.intent_classifier import IntentClassifier
from snips_inference_agl.intent_classifier.log_reg_classifier_utils import (text_to_utterance)
from snips_inference_agl.pipeline.configs import LogRegIntentClassifierConfig
from snips_inference_agl.result import intent_classification_result
logger = logging.getLogger(__name__)
# We set tol to 1e-3 to silence the following warning with Python 2 (
# scikit-learn 0.20):
#
# FutureWarning: max_iter and tol parameters have been added in SGDClassifier
# in 0.19. If max_iter is set but tol is left unset, the default value for tol
# in 0.19 and 0.20 will be None (which is equivalent to -infinity, so it has no
# effect) but will change in 0.21 to 1e-3. Specify tol to silence this warning.
LOG_REG_ARGS = {
"loss": "log",
"penalty": "l2",
"max_iter": 1000,
"tol": 1e-3,
"n_jobs": -1
}
@IntentClassifier.register("log_reg_intent_classifier")
class LogRegIntentClassifier(IntentClassifier):
"""Intent classifier which uses a Logistic Regression underneath"""
config_type = LogRegIntentClassifierConfig
def __init__(self, config=None, **shared):
"""The LogReg intent classifier can be configured by passing a
:class:`.LogRegIntentClassifierConfig`"""
super(LogRegIntentClassifier, self).__init__(config, **shared)
self.classifier = None
self.intent_list = None
self.featurizer = None
@property
def fitted(self):
"""Whether or not the intent classifier has already been fitted"""
return self.intent_list is not None
@fitted_required
def get_intent(self, text, intents_filter=None):
"""Performs intent classification on the provided *text*
Args:
text (str): Input
intents_filter (str or list of str): When defined, it will find
the most likely intent among the list, otherwise it will use
the whole list of intents defined in the dataset
Returns:
dict or None: The most likely intent along with its probability or
*None* if no intent was found
Raises:
:class:`snips_nlu.exceptions.NotTrained`: When the intent
classifier is not fitted
"""
return self._get_intents(text, intents_filter)[0]
@fitted_required
def get_intents(self, text):
"""Performs intent classification on the provided *text* and returns
the list of intents ordered by decreasing probability
The length of the returned list is exactly the number of intents in the
dataset + 1 for the None intent
Raises:
:class:`snips_nlu.exceptions.NotTrained`: when the intent
classifier is not fitted
"""
return self._get_intents(text, intents_filter=None)
def _get_intents(self, text, intents_filter):
if isinstance(intents_filter, str):
intents_filter = {intents_filter}
elif isinstance(intents_filter, list):
intents_filter = set(intents_filter)
if not text or not self.intent_list or not self.featurizer:
results = [intent_classification_result(None, 1.0)]
results += [intent_classification_result(i, 0.0)
for i in self.intent_list if i is not None]
return results
if len(self.intent_list) == 1:
return [intent_classification_result(self.intent_list[0], 1.0)]
# pylint: disable=C0103
X = self.featurizer.transform([text_to_utterance(text)])
# pylint: enable=C0103
proba_vec = self._predict_proba(X)
logger.debug(
"%s", DifferedLoggingMessage(self.log_activation_weights, text, X))
results = [
intent_classification_result(i, proba)
for i, proba in zip(self.intent_list, proba_vec[0])
if intents_filter is None or i is None or i in intents_filter]
return sorted(results, key=lambda res: -res[RES_PROBA])
def _predict_proba(self, X): # pylint: disable=C0103
import numpy as np
# self.classifier._check_proba() # pylint: disable=W0212
prob = self.classifier.decision_function(X)
prob *= -1
np.exp(prob, prob)
prob += 1
np.reciprocal(prob, prob)
if prob.ndim == 1:
return np.vstack([1 - prob, prob]).T
return prob
@classmethod
def from_path(cls, path, **shared):
"""Loads a :class:`LogRegIntentClassifier` instance from a path
The data at the given path must have been generated using
:func:`~LogRegIntentClassifier.persist`
"""
import numpy as np
from sklearn.linear_model import SGDClassifier
path = Path(path)
model_path = path / "intent_classifier.json"
if not model_path.exists():
raise LoadingError("Missing intent classifier model file: %s"
% model_path.name)
with model_path.open(encoding="utf8") as f:
model_dict = json.load(f)
# Create the classifier
config = LogRegIntentClassifierConfig.from_dict(model_dict["config"])
intent_classifier = cls(config=config, **shared)
intent_classifier.intent_list = model_dict['intent_list']
# Create the underlying SGD classifier
sgd_classifier = None
coeffs = model_dict['coeffs']
intercept = model_dict['intercept']
t_ = model_dict["t_"]
if coeffs is not None and intercept is not None:
sgd_classifier = SGDClassifier(**LOG_REG_ARGS)
sgd_classifier.coef_ = np.array(coeffs)
sgd_classifier.intercept_ = np.array(intercept)
sgd_classifier.t_ = t_
intent_classifier.classifier = sgd_classifier
# Add the featurizer
featurizer = model_dict['featurizer']
if featurizer is not None:
featurizer_path = path / featurizer
intent_classifier.featurizer = Featurizer.from_path(
featurizer_path, **shared)
return intent_classifier
def log_activation_weights(self, text, x, top_n=50):
import numpy as np
if not hasattr(self.featurizer, "feature_index_to_feature_name"):
return None
log = "\n\nTop {} feature activations for: \"{}\":\n".format(
top_n, text)
activations = np.multiply(
self.classifier.coef_, np.asarray(x.todense()))
abs_activation = np.absolute(activations).flatten().squeeze()
if top_n > activations.size:
top_n = activations.size
top_n_activations_ix = np.argpartition(abs_activation, -top_n,
axis=None)[-top_n:]
top_n_activations_ix = np.unravel_index(
top_n_activations_ix, activations.shape)
index_to_feature = self.featurizer.feature_index_to_feature_name
features_intent_and_activation = [
(self.intent_list[i], index_to_feature[f], activations[i, f])
for i, f in zip(*top_n_activations_ix)]
features_intent_and_activation = sorted(
features_intent_and_activation, key=lambda x: abs(x[2]),
reverse=True)
for intent, feature, activation in features_intent_and_activation:
log += "\n\n\"{}\" -> ({}, {:.2f})".format(
intent, feature, float(activation))
log += "\n\n"
return log
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