From 6675c9e3429ec6a89c8e08c84ce24518a52f3236 Mon Sep 17 00:00:00 2001
From: Nicolas Hug <contact@nicolas-hug.com>
Date: Tue, 4 Jun 2019 11:25:26 -0400
Subject: [PATCH] MAINT pass n_samples instead of sample_indices in GBDT
 (#14017)

---
 sklearn/ensemble/_hist_gradient_boosting/grower.py   |  2 +-
 .../ensemble/_hist_gradient_boosting/splitting.pyx   |  8 +++-----
 .../_hist_gradient_boosting/tests/test_splitting.py  | 12 ++++++------
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/sklearn/ensemble/_hist_gradient_boosting/grower.py b/sklearn/ensemble/_hist_gradient_boosting/grower.py
index 691d10f16ac61..d6836c2bd4c75 100644
--- a/sklearn/ensemble/_hist_gradient_boosting/grower.py
+++ b/sklearn/ensemble/_hist_gradient_boosting/grower.py
@@ -276,7 +276,7 @@ def _compute_best_split_and_push(self, node):
         """
 
         node.split_info = self.splitter.find_node_split(
-            node.sample_indices, node.histograms, node.sum_gradients,
+            node.n_samples, node.histograms, node.sum_gradients,
             node.sum_hessians)
 
         if node.split_info.gain <= 0:  # no valid split
diff --git a/sklearn/ensemble/_hist_gradient_boosting/splitting.pyx b/sklearn/ensemble/_hist_gradient_boosting/splitting.pyx
index 3beffff125af2..6dc6e58d9acff 100644
--- a/sklearn/ensemble/_hist_gradient_boosting/splitting.pyx
+++ b/sklearn/ensemble/_hist_gradient_boosting/splitting.pyx
@@ -319,7 +319,7 @@ cdef class Splitter:
 
     def find_node_split(
             Splitter self,
-            const unsigned int [::1] sample_indices,  # IN
+            unsigned int n_samples,
             hist_struct [:, ::1] histograms,  # IN
             const Y_DTYPE_C sum_gradients,
             const Y_DTYPE_C sum_hessians):
@@ -329,8 +329,8 @@ cdef class Splitter:
 
         Parameters
         ----------
-        sample_indices : ndarray of unsigned int, shape (n_samples_at_node,)
-            The indices of the samples at the node to split.
+        n_samples : int
+            The number of samples at the node.
         histograms : ndarray of HISTOGRAM_DTYPE of \
                 shape (n_features, max_bins)
             The histograms of the current node.
@@ -345,7 +345,6 @@ cdef class Splitter:
             The info about the best possible split among all features.
         """
         cdef:
-            int n_samples
             int feature_idx
             int best_feature_idx
             int n_features = self.n_features
@@ -353,7 +352,6 @@ cdef class Splitter:
             split_info_struct * split_infos
 
         with nogil:
-            n_samples = sample_indices.shape[0]
 
             split_infos = <split_info_struct *> malloc(
                 self.n_features * sizeof(split_info_struct))
diff --git a/sklearn/ensemble/_hist_gradient_boosting/tests/test_splitting.py b/sklearn/ensemble/_hist_gradient_boosting/tests/test_splitting.py
index 1f72eac151bba..2fa94e06830ec 100644
--- a/sklearn/ensemble/_hist_gradient_boosting/tests/test_splitting.py
+++ b/sklearn/ensemble/_hist_gradient_boosting/tests/test_splitting.py
@@ -49,7 +49,7 @@ def test_histogram_split(n_bins):
 
             histograms = builder.compute_histograms_brute(sample_indices)
             split_info = splitter.find_node_split(
-                sample_indices, histograms, sum_gradients,
+                sample_indices.shape[0], histograms, sum_gradients,
                 sum_hessians)
 
             assert split_info.bin_idx == true_bin
@@ -103,17 +103,17 @@ def test_gradient_and_hessian_sanity(constant_hessian):
                         min_samples_leaf, min_gain_to_split, constant_hessian)
 
     hists_parent = builder.compute_histograms_brute(sample_indices)
-    si_parent = splitter.find_node_split(sample_indices, hists_parent,
+    si_parent = splitter.find_node_split(n_samples, hists_parent,
                                          sum_gradients, sum_hessians)
     sample_indices_left, sample_indices_right, _ = splitter.split_indices(
         si_parent, sample_indices)
 
     hists_left = builder.compute_histograms_brute(sample_indices_left)
     hists_right = builder.compute_histograms_brute(sample_indices_right)
-    si_left = splitter.find_node_split(sample_indices_left, hists_left,
+    si_left = splitter.find_node_split(n_samples, hists_left,
                                        si_parent.sum_gradient_left,
                                        si_parent.sum_hessian_left)
-    si_right = splitter.find_node_split(sample_indices_right, hists_right,
+    si_right = splitter.find_node_split(n_samples, hists_right,
                                         si_parent.sum_gradient_right,
                                         si_parent.sum_hessian_right)
 
@@ -203,7 +203,7 @@ def test_split_indices():
     assert np.all(sample_indices == splitter.partition)
 
     histograms = builder.compute_histograms_brute(sample_indices)
-    si_root = splitter.find_node_split(sample_indices, histograms,
+    si_root = splitter.find_node_split(n_samples, histograms,
                                        sum_gradients, sum_hessians)
 
     # sanity checks for best split
@@ -256,6 +256,6 @@ def test_min_gain_to_split():
                         hessians_are_constant)
 
     histograms = builder.compute_histograms_brute(sample_indices)
-    split_info = splitter.find_node_split(sample_indices, histograms,
+    split_info = splitter.find_node_split(n_samples, histograms,
                                           sum_gradients, sum_hessians)
     assert split_info.gain == -1