primitives: Add inclusion proof benchmarks.

BenchmarkGenerateInclusionProof
-------------------------------
64_leaves     31101     38577 ns/op    2240 B/op   2 allocs/op
128_leaves    15512     77140 ns/op    4320 B/op   2 allocs/op
256_leaves     7999    155127 ns/op    8448 B/op   2 allocs/op
2048_leaves     975   1237867 ns/op   65888 B/op   2 allocs/op

BenchmarkVerifyInclusionProof
-----------------------------
64_leaves     333319   3999 ns/op   0 B/op   0 allocs/op
128_leaves    287670   4187 ns/op   0 B/op   0 allocs/op
256_leaves    249007   4841 ns/op   0 B/op   0 allocs/op
2048_leaves   181994   6683 ns/op   0 B/op   0 allocs/op

internal/staging/primitives/inclusionproof_bench_test.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2021 The Decred developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package primitives
+
+import (
+	"encoding/binary"
+	"fmt"
+	"testing"
+
+	"github.com/decred/dcrd/chaincfg/chainhash"
+)
+
+// BenchmarkGenerateInclusionProof benchmarks generating inclusion proofs for
+// various numbers of leaves.
+func BenchmarkGenerateInclusionProof(b *testing.B) {
+	for _, numLeaves := range []uint32{64, 128, 256, 2048} {
+		// Generate the specified number of leaves and choose a leaf index
+		// accordingly.
+		benchName := fmt.Sprintf("%d leaves", numLeaves)
+		leaves := make([]chainhash.Hash, 0, numLeaves)
+		for i := uint32(0); i < numLeaves; i++ {
+			var buf [4]byte
+			binary.LittleEndian.PutUint32(buf[:], i)
+			leaves = append(leaves, chainhash.HashH(buf[:]))
+		}
+		leafIndex := numLeaves / 2
+
+		b.Run(benchName, func(b *testing.B) {
+			b.ReportAllocs()
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				_ = GenerateInclusionProof(leaves, leafIndex)
+			}
+		})
+	}
+}
+
+// BenchmarkVerifyInclusionProof benchmarks verifying inclusion proofs for
+// various numbers of leaves.
+func BenchmarkVerifyInclusionProof(b *testing.B) {
+	for _, numLeaves := range []uint32{64, 128, 256, 2048} {
+		// Generate the specified number of leaves, calculate the merkle root,
+		// choose a leaf index, and  generate a proof accordingly.
+		benchName := fmt.Sprintf("%d leaves", numLeaves)
+		leaves := make([]chainhash.Hash, 0, numLeaves)
+		for i := uint32(0); i < numLeaves; i++ {
+			var buf [4]byte
+			binary.LittleEndian.PutUint32(buf[:], i)
+			leaves = append(leaves, chainhash.HashH(buf[:]))
+		}
+		root := CalcMerkleRoot(leaves)
+		leafIndex := numLeaves / 2
+		leaf := leaves[leafIndex]
+		proof := GenerateInclusionProof(leaves, leafIndex)
+
+		b.Run(benchName, func(b *testing.B) {
+			b.ReportAllocs()
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				verified := VerifyInclusionProof(&root, &leaf, leafIndex, proof)
+				if !verified {
+					b.Fatalf("%q: failed to verify proof", benchName)
+				}
+			}
+		})
+	}
+}