diff --git a/python-package/xgboost/training.py b/python-package/xgboost/training.py index ae12fd868..dbb9cca27 100644 --- a/python-package/xgboost/training.py +++ b/python-package/xgboost/training.py @@ -10,7 +10,7 @@ import numpy as np from .core import Booster, STRING_TYPES def train(params, dtrain, num_boost_round=10, evals=(), obj=None, feval=None, - early_stopping_rounds=None, evals_result=None, verbose_eval=True): + early_stopping_rounds=None, evals_result=None, verbose_eval=True, learning_rates=None): # pylint: disable=too-many-statements,too-many-branches, attribute-defined-outside-init """Train a booster with given parameters. @@ -46,6 +46,10 @@ def train(params, dtrain, num_boost_round=10, evals=(), obj=None, feval=None, verbose_eval : bool If `verbose_eval` then the evaluation metric on the validation set, if given, is printed at each boosting stage. + learning_rates: list or function + Learning rate for each boosting round (yields learning rate decay). + - list l: eta = l[boosting round] + - function f: eta = f(boosting round, num_boost_round) Returns ------- @@ -119,7 +123,15 @@ def train(params, dtrain, num_boost_round=10, evals=(), obj=None, feval=None, best_msg = '' best_score_i = 0 + if isinstance(learning_rates, list) and len(learning_rates) < num_boost_round: + raise ValueError("Length of list 'learning_rates' has to equal 'num_boost_round'.") + for i in range(num_boost_round): + if learning_rates is not None: + if isinstance(learning_rates, list): + bst.set_param({'eta': learning_rates[i]}) + else: + bst.set_param({'eta': learning_rates(i, num_boost_round)}) bst.update(dtrain, i, obj) bst_eval_set = bst.eval_set(evals, i, feval)