Random Forests
Random Forest Classifier
- class snapml.RandomForestClassifier(n_estimators=10, criterion='gini', max_depth=None, min_samples_leaf=1, max_features='auto', bootstrap=True, n_jobs=1, random_state=None, verbose=False, use_histograms=False, hist_nbins=256, use_gpu=False, gpu_ids=[0], compress_trees=False)
Random Forest Classifier
This class implements a random forest classifier using the IBM Snap ML library. It can be used for binary and multi-class classification problems.
- Parameters
- n_estimatorsinteger, default=10
This parameter defines the number of trees in forest.
- criterionstring, default=”gini”
This function measures the quality of a split. The currently supported criterion is “gini”.
- max_depthinteger or None, default=None
The maximum depth of the tree. If None, then nodes are expanded until all leaves are pure or until all leaves contain less than min_samples_leaf samples.
- min_samples_leafint or float, default=1
The minimum number of samples required to be at a leaf node. A split point at any depth will only be considered if it leaves at least
min_samples_leaf
training samples in each of the left and right branches. - If int, then consider min_samples_leaf as the minimum number. - If float, then min_samples_leaf is a fraction and ceil(min_samples_leaf * n_samples) are the minimum number of samples for each node.- max_featuresint, float, string or None, default=’auto’
- The number of features to consider when looking for the best split:
If int, then consider max_features features at each split.
If float, then max_features is a fraction and int(max_features * n_features) features are considered at each split.
If “auto”, then max_features=sqrt(n_features).
If “sqrt”, then max_features=sqrt(n_features).
If “log2”, then max_features=log2(n_features).
If None, then max_features=n_features.
- bootstrapboolean, default=True
This parameter determines whether bootstrap samples are used when building trees.
- n_jobsinteger, default=1
The number of jobs to run in parallel the fit function.
- random_stateinteger, or None, default=None
If integer, random_state is the seed used by the random number generator. If None, the random number generator is the RandomState instance used by np.random.
- verboseboolean, default=False
If True, it prints debugging information while training. Warning: this will increase the training time. For performance evaluation, use verbose=False.
- use_histogramsboolean, default=False
Use histogram-based splits rather than exact splits.
- hist_nbinsint, default=256
Number of histogram bins.
- use_gpuboolean, default=False
Use GPU acceleration (only supported for histogram-based splits).
- gpu_idsarray-like of int, default: [0]
Device IDs of the GPUs which will be used when GPU acceleration is enabled.
- compress_treesbool, default=False
Compress trees after training for fast inference.
- Attributes
- fit(X_train, y_train, sample_weight=None)
Fit the model according to the given train data.
- Parameters
- X_traindense matrix (ndarray)
Train dataset
- y_trainarray-like, shape = (n_samples,)
The target vector corresponding to X_train.
- sample_weightarray-like, shape = [n_samples] or None
Sample weights. If None, then samples are equally weighted. TODO: Splits that would create child nodes with net zero or negative weight are ignored while searching for a split in each node.
- Returns
- selfobject
- get_params(deep=True)
Get parameters for this estimator.
- Parameters
- deepbool, default=True
If True, will return the parameters for this estimator and contained subobjects that are estimators.
- Returns
- paramsdict
Parameter names mapped to their values.
- import_model(input_file, type, X=None)
Import a pre-trained forest ensemble model from the given input file of the given type. Returns an optimized Snap ML model format with compressed decision trees for fast inference.
Supported import format is (sklearn) PMML. The corresponding input file type to be provided to the import_model function is ‘pmml’.
If the input file contains features that are not supported by the import function then a runtime error is thrown indicating the feature and the line number within the input file containing the feature.
An input data set X is optional and is used to predict node access characteristics for performing the node clustering.
- Parameters
- input_filestr
Input filename
- type{‘pmml’}
Input file type
- Xdense matrix (ndarray)
Dataset used for compressing trees
- Returns
- selfobject
- predict(X, n_jobs=None)
Class/Regression predictions
The returned class/regression estimates.
- Parameters
- Xdense matrix (ndarray) or memmap (np.memmap)
Dataset used for predicting class/regression estimates.
- n_jobsint, default=None
Number of threads used to run inference. By default the value of the class attribute is used..
- Returns
- pred/proba: array-like, shape = (n_samples,)
Returns the predicted class/values of the sample.
- predict_proba(X, n_jobs=None)
Predict class probabilities.
- Parameters
- Xdense matrix (ndarray)
Dataset used for predicting probabilities.
- n_jobsint, default=None
By default the value of the class attribute is used..
- Returns
- ——-
- proba: array-like, shape = (n_samples, n_classes)
Returns the predicted probabilities the sample.
- score(X, y, sample_weight=None)
Return the mean accuracy on the given test data and labels.
In multi-label classification, this is the subset accuracy which is a harsh metric since you require for each sample that each label set be correctly predicted.
- Parameters
- Xarray-like of shape (n_samples, n_features)
Test samples.
- yarray-like of shape (n_samples,) or (n_samples, n_outputs)
True labels for X.
- sample_weightarray-like of shape (n_samples,), default=None
Sample weights.
- Returns
- scorefloat
Mean accuracy of
self.predict(X)
wrt. y.
- set_params(**params)
Set the parameters of this model.
Valid parameter keys can be listed with
get_params()
.- Returns
- self
Random Forest Regressor
- class snapml.RandomForestRegressor(n_estimators=10, criterion='mse', max_depth=None, min_samples_leaf=1, max_features='auto', bootstrap=True, n_jobs=1, random_state=None, verbose=False, use_histograms=False, hist_nbins=256, use_gpu=False, gpu_ids=[0], compress_trees=False)
Random Forest Regressor
This class implements a random forest regressor using the IBM Snap ML library. It can be used for regression tasks.
- Parameters
- n_estimatorsinteger, default=10
This parameter defines the number of trees in forest.
- criterionstring, default=”mse”
This function measures the quality of a split. The currently supported criterion is “mse”.
- max_depthinteger or None, default=None
The maximum depth of the tree. If None, then nodes are expanded until all leaves are pure or until all leaves contain less than min_samples_leaf samples.
- min_samples_leafint or float, default=1
The minimum number of samples required to be at a leaf node. A split point at any depth will only be considered if it leaves at least
min_samples_leaf
training samples in each of the left and right branches. - If int, then consider min_samples_leaf as the minimum number. - If float, then min_samples_leaf is a fraction and ceil(min_samples_leaf * n_samples) are the minimum number of samples for each node.- max_featuresint, float, string or None, default=’auto’
- The number of features to consider when looking for the best split:
If int, then consider max_features features at each split.
If float, then max_features is a fraction and int(max_features * n_features) features are considered at each split.
If “auto”, then max_features=n_features.
If “sqrt”, then max_features=sqrt(n_features).
If “log2”, then max_features=log2(n_features).
If None, then max_features=n_features.
- bootstrapboolean, default=True
This parameter determines whether bootstrap samples are used when building trees.
- n_jobsinteger, default=1
The number of jobs to run in parallel the fit function.
- random_stateinteger, or None, default=None
If integer, random_state is the seed used by the random number generator. If None, the random number generator is the RandomState instance used by np.random.
- verboseboolean, default=False
If True, it prints debugging information while training. Warning: this will increase the training time. For performance evaluation, use verbose=False.
- use_histogramsboolean, default=False
Use histogram-based splits rather than exact splits.
- hist_nbinsint, default=256
Number of histogram bins.
- use_gpuboolean, default=True
Use GPU acceleration (only supported for histogram-based splits).
- gpu_idsarray-like of int, default: [0]
Device IDs of the GPUs which will be used when GPU acceleration is enabled.
- compress_treesbool, default=False
Compress trees after training for fast inference.
- Attributes
- fit(X_train, y_train, sample_weight=None)
Fit the model according to the given train data.
- Parameters
- X_traindense matrix (ndarray)
Train dataset
- y_trainarray-like, shape = (n_samples,)
The target vector corresponding to X_train.
- sample_weightarray-like, shape = [n_samples] or None
Sample weights. If None, then samples are equally weighted. TODO: Splits that would create child nodes with net zero or negative weight are ignored while searching for a split in each node.
- Returns
- selfobject
- get_params(deep=True)
Get parameters for this estimator.
- Parameters
- deepbool, default=True
If True, will return the parameters for this estimator and contained subobjects that are estimators.
- Returns
- paramsdict
Parameter names mapped to their values.
- import_model(input_file, type, X=None)
Import a pre-trained forest ensemble model from the given input file of the given type. Returns an optimized Snap ML model format with compressed decision trees for fast inference.
Supported import format is (sklearn) PMML. The corresponding input file type to be provided to the import_model function is ‘pmml’.
If the input file contains features that are not supported by the import function then a runtime error is thrown indicating the feature and the line number within the input file containing the feature.
An input data set X is optional and is used to predict node access characteristics for performing the node clustering.
- Parameters
- input_filestr
Input filename
- type{‘pmml’}
Input file type
- Xdense matrix (ndarray)
Dataset used for compressing trees
- Returns
- selfobject
- predict(X, n_jobs=None)
Class/Regression predictions
The returned class/regression estimates.
- Parameters
- Xdense matrix (ndarray) or memmap (np.memmap)
Dataset used for predicting class/regression estimates.
- n_jobsint, default=None
Number of threads used to run inference. By default the value of the class attribute is used..
- Returns
- pred/proba: array-like, shape = (n_samples,)
Returns the predicted class/values of the sample.
- score(X, y, sample_weight=None)
Return the coefficient of determination of the prediction.
The coefficient of determination \(R^2\) is defined as \((1 - \frac{u}{v})\), where \(u\) is the residual sum of squares
((y_true - y_pred)** 2).sum()
and \(v\) is the total sum of squares((y_true - y_true.mean()) ** 2).sum()
. The best possible score is 1.0 and it can be negative (because the model can be arbitrarily worse). A constant model that always predicts the expected value of y, disregarding the input features, would get a \(R^2\) score of 0.0.- Parameters
- Xarray-like of shape (n_samples, n_features)
Test samples. For some estimators this may be a precomputed kernel matrix or a list of generic objects instead with shape
(n_samples, n_samples_fitted)
, wheren_samples_fitted
is the number of samples used in the fitting for the estimator.- yarray-like of shape (n_samples,) or (n_samples, n_outputs)
True values for X.
- sample_weightarray-like of shape (n_samples,), default=None
Sample weights.
- Returns
- scorefloat
\(R^2\) of
self.predict(X)
wrt. y.
Notes
The \(R^2\) score used when calling
score
on a regressor usesmultioutput='uniform_average'
from version 0.23 to keep consistent with default value ofr2_score()
. This influences thescore
method of all the multioutput regressors (except forMultiOutputRegressor
).
- set_params(**params)
Set the parameters of this model.
Valid parameter keys can be listed with
get_params()
.- Returns
- self