diff --git a/BitSliceIndexing/bsi.go b/BitSliceIndexing/bsi.go
index 5487edbf..16bdd6b8 100644
--- a/BitSliceIndexing/bsi.go
+++ b/BitSliceIndexing/bsi.go
@@ -754,11 +754,7 @@ func batchEqual(e *task, batch []uint32, resultsChan chan *roaring.Bitmap,
 
 // ClearBits cleared the bits that exist in the target if they are also in the found set.
 func ClearBits(foundSet, target *roaring.Bitmap) {
-	iter := foundSet.Iterator()
-	for iter.HasNext() {
-		cID := iter.Next()
-		target.Remove(cID)
-	}
+	target.AndNot(foundSet)
 }
 
 // ClearValues removes the values found in foundSet
@@ -768,13 +764,13 @@ func (b *BSI) ClearValues(foundSet *roaring.Bitmap) {
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
-		ClearBits(foundSet, b.eBM)
+		b.eBM.AndNot(foundSet)
 	}()
 	for i := 0; i < b.BitCount(); i++ {
 		wg.Add(1)
 		go func(j int) {
 			defer wg.Done()
-			ClearBits(foundSet, b.bA[j])
+			b.bA[j].AndNot(foundSet)
 		}(i)
 	}
 	wg.Wait()
diff --git a/BitSliceIndexing/bsi_test.go b/BitSliceIndexing/bsi_test.go
index a28a5d4e..71d5e7b4 100644
--- a/BitSliceIndexing/bsi_test.go
+++ b/BitSliceIndexing/bsi_test.go
@@ -2,7 +2,6 @@ package roaring
 
 import (
 	"fmt"
-	"io/ioutil"
 	"math/rand"
 	"os"
 	"testing"
@@ -35,6 +34,27 @@ func setup() *BSI {
 	return bsi
 }
 
+func setupLargeBSI(t testing.TB) *BSI {
+	t.Helper()
+
+	datEBM, err := os.ReadFile("./testdata/age/EBM")
+	if err != nil {
+		return nil
+	}
+	b := make([][]byte, 9)
+	b[0] = datEBM
+	for i := 1; i <= 8; i++ {
+		b[i], err = os.ReadFile(fmt.Sprintf("./testdata/age/%d", i))
+		if err != nil {
+			return nil
+		}
+	}
+	bsi := NewDefaultBSI()
+	err = bsi.UnmarshalBinary(b)
+	require.NoError(t, err)
+	return bsi
+}
+
 func setupNegativeBoundary() *BSI {
 
 	bsi := NewBSI(5, -5)
@@ -264,58 +284,12 @@ func TestNewBSIRetainSet(t *testing.T) {
 
 func TestLargeFile(t *testing.T) {
 
-	datEBM, err := ioutil.ReadFile("./testdata/age/EBM")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat1, err := ioutil.ReadFile("./testdata/age/1")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat2, err := ioutil.ReadFile("./testdata/age/2")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat3, err := ioutil.ReadFile("./testdata/age/3")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat4, err := ioutil.ReadFile("./testdata/age/4")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat5, err := ioutil.ReadFile("./testdata/age/5")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat6, err := ioutil.ReadFile("./testdata/age/6")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat7, err := ioutil.ReadFile("./testdata/age/7")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat8, err := ioutil.ReadFile("./testdata/age/8")
-	if err != nil {
+	bsi := setupLargeBSI(t)
+	if bsi == nil {
 		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
 		return
 	}
 
-	b := [][]byte{datEBM, dat1, dat2, dat3, dat4, dat5, dat6, dat7, dat8}
-
-	bsi := NewDefaultBSI()
-	err = bsi.UnmarshalBinary(b)
-	require.Nil(t, err)
-
 	resultA := bsi.CompareValue(0, EQ, 55, 0, nil)
 	assert.Equal(t, uint64(520157), resultA.GetCardinality())
 
@@ -468,6 +442,23 @@ func BenchmarkSetRoaring(b *testing.B) {
 	}
 }
 
+func BenchmarkClearValues(b *testing.B) {
+	bsi := setupLargeBSI(b)
+	if bsi == nil {
+		b.Skip("\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
+		return
+	}
+	resultA := bsi.CompareValue(0, EQ, 55, 0, nil)
+	assert.Equal(b, uint64(520157), resultA.GetCardinality())
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b.StopTimer()
+		b2 := bsi.Clone()
+		b.StartTimer()
+		b2.ClearValues(resultA)
+	}
+}
+
 func TestIssue426(t *testing.T) {
 	bsi := NewBSI(101, 0)
 	bsi.SetValue(3, 5)
diff --git a/roaring64/bsi64.go b/roaring64/bsi64.go
index 46dbe121..fb86d105 100644
--- a/roaring64/bsi64.go
+++ b/roaring64/bsi64.go
@@ -738,7 +738,7 @@ func (b *BSI) ParOr(parallelism int, bsis ...*BSI) {
 	bits := len(b.bA)
 	for i := 0; i < len(bsis); i++ {
 		if len(bsis[i].bA) > bits {
-			bits = len(bsis[i].bA )
+			bits = len(bsis[i].bA)
 		}
 	}
 
@@ -942,11 +942,7 @@ func batchEqual(e *task, batch []uint64, resultsChan chan *Bitmap,
 
 // ClearBits cleared the bits that exist in the target if they are also in the found set.
 func ClearBits(foundSet, target *Bitmap) {
-	iter := foundSet.Iterator()
-	for iter.HasNext() {
-		cID := iter.Next()
-		target.Remove(cID)
-	}
+	target.AndNot(foundSet)
 }
 
 // ClearValues removes the values found in foundSet
@@ -956,13 +952,13 @@ func (b *BSI) ClearValues(foundSet *Bitmap) {
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
-		ClearBits(foundSet, &b.eBM)
+		b.eBM.AndNot(foundSet)
 	}()
 	for i := 0; i < b.BitCount(); i++ {
 		wg.Add(1)
 		go func(j int) {
 			defer wg.Done()
-			ClearBits(foundSet, &b.bA[j])
+			b.bA[j].AndNot(foundSet)
 		}(i)
 	}
 	wg.Wait()
diff --git a/roaring64/bsi64_test.go b/roaring64/bsi64_test.go
index 98b4aba0..3eba0e9e 100644
--- a/roaring64/bsi64_test.go
+++ b/roaring64/bsi64_test.go
@@ -214,6 +214,27 @@ func setupRandom() (bsi *BSI, min, max int64) {
 	return bsi, min, max
 }
 
+func setupLargeBSI(t testing.TB) *BSI {
+	t.Helper()
+
+	datEBM, err := os.ReadFile("./testdata/age/EBM")
+	if err != nil {
+		return nil
+	}
+	b := make([][]byte, 9)
+	b[0] = datEBM
+	for i := 1; i <= 8; i++ {
+		b[i], err = os.ReadFile(fmt.Sprintf("./testdata/age/%d", i))
+		if err != nil {
+			return nil
+		}
+	}
+	bsi := NewDefaultBSI()
+	err = bsi.UnmarshalBinary(b)
+	require.NoError(t, err)
+	return bsi
+}
+
 func TestTwosComplement(t *testing.T) {
 	assert.Equal(t, "1001110", twosComplement(big.NewInt(-50), 7).Text(2))
 	assert.Equal(t, "110010", twosComplement(big.NewInt(50), 7).Text(2))
@@ -408,59 +429,12 @@ func TestNewBSIRetainSet(t *testing.T) {
 
 func TestLargeFile(t *testing.T) {
 
-	datEBM, err := ioutil.ReadFile("./testdata/age/EBM")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat1, err := ioutil.ReadFile("./testdata/age/1")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat2, err := ioutil.ReadFile("./testdata/age/2")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat3, err := ioutil.ReadFile("./testdata/age/3")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat4, err := ioutil.ReadFile("./testdata/age/4")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat5, err := ioutil.ReadFile("./testdata/age/5")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat6, err := ioutil.ReadFile("./testdata/age/6")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat7, err := ioutil.ReadFile("./testdata/age/7")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
-		return
-	}
-	dat8, err := ioutil.ReadFile("./testdata/age/8")
-	if err != nil {
+	bsi := setupLargeBSI(t)
+	if bsi == nil {
 		fmt.Fprintf(os.Stderr, "\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
 		return
 	}
 
-	b := [][]byte{datEBM, dat1, dat2, dat3, dat4, dat5, dat6, dat7, dat8}
-
-	bsi := NewDefaultBSI()
-	//bsi.RunOptimize()
-	err = bsi.UnmarshalBinary(b)
-	require.Nil(t, err)
-
 	resultA := bsi.CompareValue(0, EQ, 55, 0, nil)
 	assert.Equal(t, uint64(574600), resultA.GetCardinality())
 
@@ -822,3 +796,21 @@ func TestRangeNilBig(t *testing.T) {
 	tmpAll := bsi.CompareBigValue(0, RANGE, bsi.MinMaxBig(0, MIN, nil), bsi.MinMaxBig(0, MAX, nil), nil)
 	assert.Equal(t, tmpAll.GetCardinality(), setAll.GetCardinality())
 }
+
+func BenchmarkClearValues(b *testing.B) {
+	bsi := setupLargeBSI(b)
+	if bsi == nil {
+		b.Skip("\n\nIMPORTANT: For testing file IO, the roaring library requires disk access.\nWe omit some tests for now.\n\n")
+		return
+	}
+	resultA := bsi.CompareValue(0, EQ, 55, 0, nil)
+
+	assert.Equal(b, uint64(574600), resultA.GetCardinality())
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b.StopTimer()
+		b2 := bsi.Clone()
+		b.StartTimer()
+		b2.ClearValues(resultA)
+	}
+}