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# coding: utf-8
# pylint: disable=too-many-locals, too-many-arguments, invalid-name
# pylint: disable=too-many-branches, too-many-statements
"""Training Library containing training routines."""
from __future__ import absolute_import

import warnings
import numpy as np
from .core import Booster, STRING_TYPES, XGBoostError, CallbackEnv, EarlyStopException
from .compat import (SKLEARN_INSTALLED, XGBStratifiedKFold)
from . import rabit
from . import callback


def _train_internal(params, dtrain,
                    num_boost_round=10, evals=(),
                    obj=None, feval=None,
                    xgb_model=None, callbacks=None):
    """internal training function"""
    callbacks = [] if callbacks is None else callbacks
    evals = list(evals)
    if isinstance(params, dict) \
            and 'eval_metric' in params \
            and isinstance(params['eval_metric'], list):
        params = dict((k, v) for k, v in params.items())
        eval_metrics = params['eval_metric']
        params.pop("eval_metric", None)
        params = list(params.items())
        for eval_metric in eval_metrics:
            params += [('eval_metric', eval_metric)]

    bst = Booster(params, [dtrain] + [d[0] for d in evals])
    nboost = 0
    num_parallel_tree = 1

    if xgb_model is not None:
        if not isinstance(xgb_model, STRING_TYPES):
            xgb_model = xgb_model.save_raw()
        bst = Booster(params, [dtrain] + [d[0] for d in evals], model_file=xgb_model)
        nboost = len(bst.get_dump())

    _params = dict(params) if isinstance(params, list) else params

    if 'num_parallel_tree' in _params:
        num_parallel_tree = _params['num_parallel_tree']
        nboost //= num_parallel_tree
    if 'num_class' in _params:
        nboost //= _params['num_class']

    # Distributed code: Load the checkpoint from rabit.
    version = bst.load_rabit_checkpoint()
    assert(rabit.get_world_size() != 1 or version == 0)
    rank = rabit.get_rank()
    start_iteration = int(version / 2)
    nboost += start_iteration

    callbacks_before_iter = [
        cb for cb in callbacks if cb.__dict__.get('before_iteration', False)]
    callbacks_after_iter = [
        cb for cb in callbacks if not cb.__dict__.get('before_iteration', False)]