Remove old parallel related code

lib/trie/branch/encode_test.go

@@ -31,7 +31,6 @@ func Test_Branch_Encode(t *testing.T) {
 	testCases := map[string]struct {
 		branch     *Branch
 		writes     []writeCall
-		parallel   bool
 		wrappedErr error
 		errMessage string
 	}{
@@ -179,71 +178,6 @@ func Test_Branch_Encode(t *testing.T) {
 				"cannot encode child at index 3: " +
 				"failed to write child to buffer: test error",
 		},
-		"buffer write error for children encoded in parallel": {
-			branch: &Branch{
-				Key:   []byte{1, 2, 3},
-				Value: []byte{100},
-				Children: [16]node.Node{
-					nil, nil, nil, &leaf.Leaf{Key: []byte{9}},
-					nil, nil, nil, &leaf.Leaf{Key: []byte{11}},
-				},
-			},
-			writes: []writeCall{
-				{ // header
-					written: []byte{195},
-				},
-				{ // key LE
-					written: []byte{1, 35},
-				},
-				{ // children bitmap
-					written: []byte{136, 0},
-				},
-				{ // value
-					written: []byte{4, 100},
-				},
-				{ // first children
-					written: []byte{12, 65, 9, 0},
-					err:     errTest,
-				},
-			},
-			parallel:   true,
-			wrappedErr: errTest,
-			errMessage: "cannot encode children of branch: " +
-				"cannot encode child at index 3: " +
-				"failed to write child to buffer: " +
-				"test error",
-		},
-		"success with parallel children encoding": {
-			branch: &Branch{
-				Key:   []byte{1, 2, 3},
-				Value: []byte{100},
-				Children: [16]node.Node{
-					nil, nil, nil, &leaf.Leaf{Key: []byte{9}},
-					nil, nil, nil, &leaf.Leaf{Key: []byte{11}},
-				},
-			},
-			writes: []writeCall{
-				{ // header
-					written: []byte{195},
-				},
-				{ // key LE
-					written: []byte{1, 35},
-				},
-				{ // children bitmap
-					written: []byte{136, 0},
-				},
-				{ // value
-					written: []byte{4, 100},
-				},
-				{ // first children
-					written: []byte{12, 65, 9, 0},
-				},
-				{ // second children
-					written: []byte{12, 65, 11, 0},
-				},
-			},
-			parallel: true,
-		},
 		"success with sequential children encoding": {
 			branch: &Branch{
 				Key:   []byte{1, 2, 3},

lib/trie/trie.go

@@ -27,7 +27,6 @@ type Trie struct {
 	root        node.Node
 	childTries  map[common.Hash]*Trie // Used to store the child tries.
 	deletedKeys []common.Hash
-	parallel    bool
 }
 
 // NewEmptyTrie creates a trie with a nil root
@@ -42,7 +41,6 @@ func NewTrie(root node.Node) *Trie {
 		childTries:  make(map[common.Hash]*Trie),
 		generation:  0, // Initially zero but increases after every snapshot.
 		deletedKeys: make([]common.Hash, 0),
-		parallel:    true,
 	}
 }
 
@@ -54,7 +52,6 @@ func (t *Trie) Snapshot() *Trie {
 			generation:  c.generation + 1,
 			root:        c.root,
 			deletedKeys: make([]common.Hash, 0),
-			parallel:    c.parallel,
 		}
 	}
 
@@ -63,7 +60,6 @@ func (t *Trie) Snapshot() *Trie {
 		root:        t.root,
 		childTries:  children,
 		deletedKeys: make([]common.Hash, 0),
-		parallel:    t.parallel,
 	}
 
 	return newTrie

lib/trie/trie_test.go

@@ -1131,35 +1131,12 @@ func Benchmark_Trie_Hash(b *testing.B) {
 		trie.Put(test.key, test.value)
 	}
 
-	trieTwo, err := trie.DeepCopy()
-	require.NoError(b, err)
-
-	b.Run("Sequential hash", func(b *testing.B) {
-		trie.parallel = false
-
-		b.StartTimer()
-		_, err := trie.Hash()
-		b.StopTimer()
-
-		require.NoError(b, err)
-
-		printMemUsage()
-	})
+	b.StartTimer()
+	_, err := trie.Hash()
+	b.StopTimer()
 
-	b.Run("Parallel hash", func(b *testing.B) {
-		trieTwo.parallel = true
-
-		b.StartTimer()
-		_, err := trieTwo.Hash()
-		b.StopTimer()
-
-		require.NoError(b, err)
-
-		printMemUsage()
-	})
-}
+	require.NoError(b, err)
 
-func printMemUsage() {
 	var m runtime.MemStats
 	runtime.ReadMemStats(&m)
 	// For info on each, see: https://golang.org/pkg/runtime/#MemStats