Use column names for predict with Daru [skip ci]

Author: ankane

lib/lightgbm/booster.rb

@@ -141,7 +141,7 @@ def num_trees
     def predict(input, start_iteration: nil, num_iteration: nil, **params)
       input =
         if daru?(input)
-          input.map_rows(&:to_a)
+          input[*cached_feature_name].map_rows(&:to_a)
         elsif input.is_a?(Hash) # sort feature.values to match the order of model.feature_name
           sorted_feature_values(input)
         elsif input.is_a?(Array) && input.first.is_a?(Hash) # on multiple elems, if 1st is hash, assume they all are

test/booster_test.rb

@@ -50,6 +50,16 @@ def test_predict_hash
     end
   end
 
+  def test_predict_daru
+    x_test =
+      Daru::DataFrame.new([
+        {"x3" => 9.0, "x2" => 7.2, "x1" => 1.2, "x0" => 3.7},
+        {"x3" => 0.0, "x2" => 7.9, "x1" => 0.5, "x0" => 7.5},
+      ])
+    pred = booster.predict(x_test)
+    assert_elements_in_delta [0.9823112229173586, 0.9583143724610858], pred.first(2)
+  end
+
   def test_predict_rover
     require "rover"
     x_test =