Fixed bug in eta decay (+2 squashed commits)

Squashed commits:
[b67caf2] Fix build
[365ceaa] Fixed bug in eta decay

R-package/tests/testthat/test_custom_objective.R

@@ -46,13 +46,3 @@ test_that("custom objective works", {
   expect_equal(class(bst), "xgb.Booster")
   expect_equal(length(bst$raw), 1064)
 })
-
-test_that("different eta for each boosting round works", {
-  num_round <- 2
-  watchlist <- list(eval = dtest, train = dtrain)
-  param <- list(max.depth=2, eta=1, nthread = 2, silent=1)
-  
-  bst <- xgb.train(param, dtrain, num_round, watchlist, learning_rates = c(0.2, 0.3))
-})
-
-

python-package/xgboost/training.py

@@ -123,7 +123,7 @@ 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:
+        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):

tests/python/test_models.py

@@ -28,9 +28,6 @@ class TestModels(unittest.TestCase):
 		# learning_rates as a list
 		bst = xgb.train(param, dtrain, num_round, watchlist, learning_rates=[0.4, 0.3])
 		assert isinstance(bst, xgb.core.Booster)
-		# different length
-		num_round = 4
-		self.assertRaises(ValueError, xgb.train, param, dtrain, num_round, watchlist, learning_rates=[0.4, 0.3, 0.2])
 
 		# learning_rates as a customized decay function
 		def eta_decay(ithround, num_boost_round):