Merge pull request #441 from RoaringBitmap/issue440

fix: make RunOptimize idempotent

Author: lemire

arraycontainer.go

@@ -1233,7 +1233,7 @@ func (ac *arrayContainer) toEfficientContainer() container {
 	card := ac.getCardinality()
 	sizeAsArrayContainer := arrayContainerSizeInBytes(card)
 
-	if sizeAsRunContainer <= minOfInt(sizeAsBitmapContainer, sizeAsArrayContainer) {
+	if sizeAsRunContainer < minOfInt(sizeAsBitmapContainer, sizeAsArrayContainer) {
 		return newRunContainer16FromArray(ac)
 	}
 	if card <= arrayDefaultMaxSize {

bitmapcontainer.go

@@ -1187,7 +1187,7 @@ func (bc *bitmapContainer) toEfficientContainer() container {
 	card := bc.getCardinality()
 	sizeAsArrayContainer := arrayContainerSizeInBytes(card)
 
-	if sizeAsRunContainer <= minOfInt(sizeAsBitmapContainer, sizeAsArrayContainer) {
+	if sizeAsRunContainer < minOfInt(sizeAsBitmapContainer, sizeAsArrayContainer) {
 		return newRunContainer16FromBitmapContainer(bc)
 	}
 	if card <= arrayDefaultMaxSize {

roaring_test.go

@@ -13,6 +13,18 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestIssue440(t *testing.T) {
+	a := NewBitmap()
+	a.AddMany([]uint32{1, 2, 3})
+	a.RunOptimize()
+	b1, err := a.MarshalBinary()
+	require.NoError(t, err)
+	a.RunOptimize()
+	b2, err := a.MarshalBinary()
+	require.NoError(t, err)
+	require.Equal(t, b1, b2)
+}
+
 func checkValidity(t *testing.T, rb *Bitmap) {
 	t.Helper()