fix: VarOptItemsSketch update

sampling/reservoir_items_sketch.go

@@ -30,18 +30,7 @@ import (
 	"github.com/apache/datasketches-go/internal"
 )
 
-// ResizeFactor controls how the internal array grows.
-// Note: Go's slice append has automatic resizing, so this is kept for
-// API compatibility with the Java version. Can be removed if not needed.
-// TODO: In Java, this is abstracted into a common package. Consider if this should be moved to a common package in the future.
-type ResizeFactor int
-
 const (
-	ResizeX1 ResizeFactor = 1
-	ResizeX2 ResizeFactor = 2
-	ResizeX4 ResizeFactor = 4
-	ResizeX8 ResizeFactor = 8
-
 	defaultResizeFactor = ResizeX8
 	minK                = 2
 
@@ -95,7 +84,7 @@ func NewReservoirItemsSketch[T any](
 
 	ceilingLgK, _ := internal.ExactLog2(common.CeilingPowerOf2(k))
 	initialLgSize := startingSubMultiple(
-		ceilingLgK, int(math.Log2(float64(options.resizeFactor))), minLgArrItems,
+		ceilingLgK, int(float64(options.resizeFactor)), minLgArrItems,
 	)
 	return &ReservoirItemsSketch[T]{
 		k:    k,

sampling/sampling.go

@@ -0,0 +1,31 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sampling
+
+// ResizeFactor controls how the internal array grows.
+// Note: Go's slice append has automatic resizing, so this is kept for
+// API compatibility with the Java version. Can be removed if not needed.
+// TODO: In Java, this is abstracted into a common package. Consider if this should be moved to a common package in the future.
+type ResizeFactor int
+
+const (
+	ResizeX1 ResizeFactor = 0
+	ResizeX2 ResizeFactor = 1
+	ResizeX4 ResizeFactor = 2
+	ResizeX8 ResizeFactor = 3
+)