From aa464ae254341e281ff2a6496d186a7ff6c2649f Mon Sep 17 00:00:00 2001
From: Marsel Mavletkulov <mmavletkulov@maxmind.com>
Date: Mon, 29 Jul 2024 14:12:22 -0400
Subject: [PATCH 1/2] Save 48 bytes per Node

---
 parse.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/parse.go b/parse.go
index 1135336..8926063 100644
--- a/parse.go
+++ b/parse.go
@@ -62,19 +62,19 @@ type Tree struct {
 
 // Node is a node in the Tree.
 type Node struct {
-	Data  NodeData
 	Left  *Node
 	Right *Node
+	Data  NodeData
 }
 
 // NodeData is a Node's data.
 type NodeData struct {
-	BaseWeight     float32
-	DefaultLeft    bool
 	ID             int
-	SplitCondition float32
 	SplitIndex     int
+	SplitCondition float32
 	SumHessian     float32
+	BaseWeight     float32
+	DefaultLeft    bool
 }
 
 // IsLeaf returns whether the Node is a leaf.

From 7d5765edc0d81c93b0aa666c7a347df99fff16f2 Mon Sep 17 00:00:00 2001
From: Marsel Mavletkulov <mmavletkulov@maxmind.com>
Date: Mon, 29 Jul 2024 15:34:19 -0400
Subject: [PATCH 2/2] Reduce parseModel() allocs by 29.8%

---
 contributions.go |  2 +-
 parse.go         | 12 ++++--------
 parse_test.go    | 14 ++++++++++++++
 3 files changed, 19 insertions(+), 9 deletions(-)
 create mode 100644 parse_test.go

diff --git a/contributions.go b/contributions.go
index ff86c01..b7010a4 100644
--- a/contributions.go
+++ b/contributions.go
@@ -280,7 +280,7 @@ func treeShap(
 	isMissing := features[splitIndex] == nil // nil means missing.
 	hotIndex := getNextNode(
 		hasMissing,
-		node,
+		&node,
 		nodeIndex,
 		features[splitIndex],
 		isMissing,
diff --git a/parse.go b/parse.go
index 8926063..626065f 100644
--- a/parse.go
+++ b/parse.go
@@ -56,7 +56,7 @@ type TreeParam struct {
 // Tree is one tree in an XGBoost model. It's the representation we process
 // XGBTree into.
 type Tree struct {
-	Nodes    []*Node // Index 0 is the root.
+	Nodes    []Node // Index 0 is the root.
 	NumNodes int
 }
 
@@ -136,11 +136,7 @@ func parseTree(
 		return nil, fmt.Errorf("getting num nodes as int64: %w", err)
 	}
 
-	var nodes []*Node
-	for i := 0; i < int(numNodes); i++ {
-		nodes = append(nodes, &Node{})
-	}
-
+	nodes := make([]Node, numNodes)
 	for i := 0; i < int(numNodes); i++ {
 		nodes[i].Data = NodeData{
 			BaseWeight:     xt.BaseWeights[i],
@@ -158,8 +154,8 @@ func parseTree(
 			continue
 		}
 
-		nodes[i].Left = nodes[left]
-		nodes[i].Right = nodes[right]
+		nodes[i].Left = &nodes[left]
+		nodes[i].Right = &nodes[right]
 	}
 
 	return &Tree{
diff --git a/parse_test.go b/parse_test.go
new file mode 100644
index 0000000..69f2ae8
--- /dev/null
+++ b/parse_test.go
@@ -0,0 +1,14 @@
+package xgbshap
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func BenchmarkParseModel(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, _, err := parseModel("testdata/small-model/model.json")
+		require.NoError(b, err)
+	}
+}