diff --git a/roaring/roaring.go b/roaring/roaring.go
index 80dbfa79a..49357620b 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -929,7 +929,7 @@ func (itr *Iterator) Next() (v uint64, eof bool) {
 		itr.j++
 
 		// Find first non-zero bit in current bitmap, if possible.
-		hb := int(itr.j / 64)
+		hb := int(itr.j >> 6)
 
 		if hb >= len(c.bitmap) {
 			itr.i, itr.j = itr.i+1, -1
@@ -944,7 +944,7 @@ func (itr *Iterator) Next() (v uint64, eof bool) {
 		// Otherwise iterate through remaining bitmaps to find next bit.
 		for hb++; hb < len(c.bitmap); hb++ {
 			if c.bitmap[hb] != 0 {
-				itr.j = int(hb*64) + trailingZeroN(c.bitmap[hb])
+				itr.j = int(hb<<6) + trailingZeroN(c.bitmap[hb])
 				return itr.peek(), false
 			}
 		}
@@ -1909,7 +1909,7 @@ func intersectionCountArrayBitmapOld(a, b *container) (n uint64) {
 
 func intersectionCountArrayBitmap(a, b *container) (n uint64) {
 	for _, val := range a.array {
-		i := val / 64
+		i := val >> 6
 		if i >= uint32(len(b.bitmap)) {
 			break
 		}
@@ -2052,8 +2052,8 @@ func intersectBitmapRun(a, b *container) *container {
 		}
 		for j := 0; j < len(b.runs); j++ {
 			vb := b.runs[j]
-			i := vb.start / 64 // index into a
-			vastart := 64 * i
+			i := vb.start >> 6 // index into a
+			vastart := i << 6
 			valast := vastart + 63
 			for valast >= vb.start && vastart <= vb.last {
 				if vastart >= vb.start && valast <= vb.last { // a within b
@@ -2077,7 +2077,7 @@ func intersectBitmapRun(a, b *container) *container {
 				}
 				// update loop vars
 				i++
-				vastart = 64 * i
+				vastart = i << 6
 				valast = vastart + 63
 			}
 		}
@@ -2300,8 +2300,8 @@ const maxBitmap = 0xFFFFFFFFFFFFFFFF
 
 // sets all bits in [i, j) (c must be a bitmap container)
 func (c *container) bitmapSetRange(i, j uint64) {
-	x := i / 64
-	y := (j - 1) / 64
+	x := i >> 6
+	y := (j - 1) >> 6
 	var X uint64 = maxBitmap << (i % 64)
 	var Y uint64 = maxBitmap >> (64 - (j % 64))
 	xcnt := popcnt(X)
@@ -2323,8 +2323,8 @@ func (c *container) bitmapSetRange(i, j uint64) {
 
 // xor's all bits in [i, j) with all true (c must be a bitmap container).
 func (c *container) bitmapXorRange(i, j uint64) {
-	x := i / 64
-	y := (j - 1) / 64
+	x := i >> 6
+	y := (j - 1) >> 6
 	var X uint64 = maxBitmap << (i % 64)
 	var Y uint64 = maxBitmap >> (64 - (j % 64))
 	if x == y {
@@ -2348,8 +2348,8 @@ func (c *container) bitmapXorRange(i, j uint64) {
 
 // zeroes all bits in [i, j) (c must be a bitmap container)
 func (c *container) bitmapZeroRange(i, j uint64) {
-	x := i / 64
-	y := (j - 1) / 64
+	x := i >> 6
+	y := (j - 1) >> 6
 	var X uint64 = maxBitmap << (i % 64)
 	var Y uint64 = maxBitmap >> (64 - (j % 64))
 	if x == y {
diff --git a/roaring/roaring_internal_test.go b/roaring/roaring_internal_test.go
index 291036ef8..0b103ae5f 100644
--- a/roaring/roaring_internal_test.go
+++ b/roaring/roaring_internal_test.go
@@ -1929,3 +1929,32 @@ func TestRunBinSearch(t *testing.T) {
 		}
 	}
 }
+func TestBitmap_RemoveEmptyContainers(t *testing.T) {
+	bm1 := NewBitmap(1<<16, 2<<16, 3<<16)
+	bm1.Remove(2 << 16)
+	if bm1.countEmptyContainers() != 1 {
+		t.Fatalf("Should be 1 empty container ")
+	}
+	bm1.removeEmptyContainers()
+
+	if bm1.countEmptyContainers() != 0 {
+		t.Fatalf("Should be no empty containers ")
+	}
+}
+
+func TestBitmap_BitmapWriteToWithEmpty(t *testing.T) {
+	bm1 := NewBitmap(1<<16, 2<<16, 3<<16)
+	bm1.Remove(2 << 16)
+	var buf bytes.Buffer
+	if _, err := bm1.WriteTo(&buf); err != nil {
+		t.Fatalf("Failure to write to bitmap buffer. ")
+	}
+	bm0 := NewBitmap()
+	bm0.UnmarshalBinary(buf.Bytes())
+	if bm0.countEmptyContainers() != 0 {
+		t.Fatalf("Should be no empty containers ")
+	}
+	if bm0.Count() != bm1.Count() {
+		t.Fatalf("Counts do not match after a marshal %d %d", bm0.Count(), bm1.Count())
+	}
+}
diff --git a/roaring/roaring_test.go b/roaring/roaring_test.go
index 8150f4376..ba24ecd22 100644
--- a/roaring/roaring_test.go
+++ b/roaring/roaring_test.go
@@ -15,8 +15,8 @@
 package roaring_test
 
 import (
-	"fmt"
 	"bytes"
+	"fmt"
 	"math"
 	"math/rand"
 	"reflect"
@@ -166,7 +166,6 @@ func TestBitmap_CountRange(t *testing.T) {
 	if n := bm0.CountRange(0, 1); n != 1 {
 		t.Fatalf("unexpected n: %d", n)
 	}
-
 }
 
 func TestBitmap_Intersection(t *testing.T) {
@@ -418,6 +417,21 @@ func TestBitmap_IntersectionCount_BitmapBitmap(t *testing.T) {
 		t.Fatalf("unexpected n (reverse): %d", n)
 	}
 }
+func TestBitmap_IntersectionCount_Mixed(t *testing.T) {
+	bm0 := testBM()
+	bm1 := roaring.NewBitmap(0, 1, 2, 3, 4, 5, 6, 7, 9, 10, 65536)
+	bm3 := roaring.NewBitmap(131072)
+
+	if n := bm0.IntersectionCount(bm0); n != bm0.Count() {
+		t.Fatalf("unexpected n: %d", n)
+	}
+	if n := bm0.IntersectionCount(bm1); n != 1 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+	if n := bm0.IntersectionCount(bm3); n != 1 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+}
 
 func TestBitmap_Quick_Array1(t *testing.T)     { testBitmapQuick(t, 1000, 1000, 2000) }
 func TestBitmap_Quick_Array2(t *testing.T)     { testBitmapQuick(t, 10000, 0, 1000) }
@@ -585,6 +599,42 @@ func TestIterator(t *testing.T) {
 	}
 }
 
+//testBM creates a bitmap with 3 containers(an array,bitmap, and run)
+func testBM() *roaring.Bitmap {
+	bm := roaring.NewBitmap()
+	//the array
+	for i := uint64(0); i < 1024; i += 4 {
+		bm.Add((1 << 16) + i)
+	}
+	//the bitmap
+	for i := uint64(0); i < 16384; i += 2 {
+		bm.Add((2 << 16) + i)
+	}
+	//small run
+	for i := uint64(0); i < 1024; i += 1 {
+		bm.Add((3 << 16) + i)
+	}
+	//large run
+	for i := uint64(0); i < 65535; i += 1 {
+		bm.Add((4 << 16) + i)
+	}
+	return bm
+}
+
+func TestBitmapOffsetRange(t *testing.T) {
+	bm := testBM()
+
+	bm1 := bm.OffsetRange(0, 0, 327680)
+	if bm1.Count() != bm.Count() {
+		t.Fatalf("Not Equal %d %d", bm1.Count(), bm.Count())
+	}
+	bm1 = bm.OffsetRange(0, 0, 131072)
+	if bm1.Count() != 256 {
+		t.Fatalf("Not Equal %d %d", bm1.Count(), 256)
+	}
+
+}
+
 var benchmarkBitmapIntersectionCountData struct {
 	a, b *roaring.Bitmap
 }