From 8582089f8ec5d1ee912fa46892196c813a7c62e8 Mon Sep 17 00:00:00 2001
From: jinlow <james.inlow@lexisnexisrisk.com>
Date: Tue, 12 Sep 2023 07:33:53 -0500
Subject: [PATCH] Small tweak

---
 src/splitter.rs | 86 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 65 insertions(+), 21 deletions(-)

diff --git a/src/splitter.rs b/src/splitter.rs
index e093385..0e8fced 100644
--- a/src/splitter.rs
+++ b/src/splitter.rs
@@ -348,28 +348,72 @@ impl Splitter for MissingBranchSplitter {
             return None;
         }
 
-        let mut left_weight = constrained_weight(
-            &self.l2,
-            left_gradient,
-            left_hessian,
-            lower_bound,
-            upper_bound,
-            constraint,
-        );
-        let mut right_weight = constrained_weight(
-            &self.l2,
-            right_gradient,
-            right_hessian,
-            lower_bound,
-            upper_bound,
-            constraint,
-        );
+        let (left_weight, right_weight) = if self.force_children_to_bound_parent {
+            // What if we made it proportional to the size of the
+            // cover in each node?
+            let l_p = left_hessian / (right_hessian + left_hessian);
+            let r_p = left_hessian / (right_hessian + left_hessian);
 
-        if self.force_children_to_bound_parent {
-            (left_weight, right_weight) = bound_to_parent(parent_weight, left_weight, right_weight);
-            assert!(between(lower_bound, upper_bound, left_weight));
-            assert!(between(lower_bound, upper_bound, right_weight));
-        }
+            (
+                constrained_weight(
+                    &self.l2,
+                    left_gradient + missing_gradient * l_p,
+                    left_hessian + missing_hessian * l_p,
+                    lower_bound,
+                    upper_bound,
+                    constraint,
+                ),
+                constrained_weight(
+                    &self.l2,
+                    right_gradient + missing_gradient * r_p,
+                    right_hessian + missing_hessian * r_p,
+                    lower_bound,
+                    upper_bound,
+                    constraint,
+                ),
+            )
+        } else {
+            (
+                constrained_weight(
+                    &self.l2,
+                    left_gradient,
+                    left_hessian,
+                    lower_bound,
+                    upper_bound,
+                    constraint,
+                ),
+                constrained_weight(
+                    &self.l2,
+                    right_gradient,
+                    right_hessian,
+                    lower_bound,
+                    upper_bound,
+                    constraint,
+                ),
+            )
+        };
+        // let mut left_weight = constrained_weight(
+        //     &self.l2,
+        //     left_gradient,
+        //     left_hessian,
+        //     lower_bound,
+        //     upper_bound,
+        //     constraint,
+        // );
+        // let mut right_weight = constrained_weight(
+        //     &self.l2,
+        //     right_gradient,
+        //     right_hessian,
+        //     lower_bound,
+        //     upper_bound,
+        //     constraint,
+        // );
+
+        // if self.force_children_to_bound_parent {
+        //     (left_weight, right_weight) = bound_to_parent(parent_weight, left_weight, right_weight);
+        //     assert!(between(lower_bound, upper_bound, left_weight));
+        //     assert!(between(lower_bound, upper_bound, right_weight));
+        // }
 
         let left_gain = gain_given_weight(&self.l2, left_gradient, left_hessian, left_weight);
         let right_gain = gain_given_weight(&self.l2, right_gradient, right_hessian, right_weight);