Improve capacity allocation in DumpCoordinates for MultiPoint

geom/bitset.go

@@ -1,5 +1,7 @@
 package geom
 
+import "math/bits"
+
 // BitSet is a set data structure that holds a mapping from non-negative
 // integers to boolean values (bits). The zero value is the BitSet with all
 // bits set to false.
@@ -36,6 +38,15 @@ func (b *BitSet) Set(i int, newVal bool) {
 	}
 }
 
+// CountTrue counts the number of elements in the set that are true.
+func (b *BitSet) CountTrue() int {
+	var count int
+	for _, mask := range b.masks {
+		count += bits.OnesCount64(mask)
+	}
+	return count
+}
+
 // Clone makes a deep copy of the BitSet.
 func (b *BitSet) Clone() BitSet {
 	return BitSet{append([]uint64(nil), b.masks...)}

geom/bitset_test.go

@@ -16,8 +16,10 @@ func TestBitSet(t *testing.T) {
 				expectFalse(t, s.Get(i))
 				s.Set(i, true)
 				expectTrue(t, s.Get(i))
+				expectIntEq(t, s.CountTrue(), 1)
 				s.Set(i, false)
 				expectFalse(t, s.Get(i))
+				expectIntEq(t, s.CountTrue(), 0)
 			})
 		}
 	})
@@ -30,9 +32,14 @@ func TestBitSet(t *testing.T) {
 			choice := rnd.Intn(n)
 			want[choice] = !want[choice]
 			s.Set(choice, want[choice])
+			var wantCountTrue int
 			for j := 0; j < n; j++ {
 				expectBoolEq(t, s.Get(j), want[j])
+				if want[j] {
+					wantCountTrue++
+				}
 			}
+			expectIntEq(t, s.CountTrue(), wantCountTrue)
 		}
 	})
 }

geom/type_multi_point.go

@@ -299,21 +299,14 @@ func (m MultiPoint) Dump() []Point {
 // a Sequence.
 func (m MultiPoint) DumpCoordinates() Sequence {
 	n := m.seq.Length()
-	var empty int
-	for i := 0; i < n; i++ {
-		if m.empty.Get(i) {
-			empty++
-		}
-	}
-
+	empty := m.empty.CountTrue()
 	nonEmpty := make([]float64, 0, n-empty)
 	for i := 0; i < n; i++ {
 		if m.empty.Get(i) {
 			continue
 		}
 		nonEmpty = m.seq.Get(i).appendFloat64s(nonEmpty)
 	}
-
 	seq := NewSequence(nonEmpty, m.seq.CoordinatesType())
 	seq.assertNoUnusedCapacity()
 	return seq