diff --git a/datasketches-cpp/fi/include/frequent_items_sketch.hpp b/datasketches-cpp/fi/include/frequent_items_sketch.hpp
index 6efe2b9..b2a9b86 100644
--- a/datasketches-cpp/fi/include/frequent_items_sketch.hpp
+++ b/datasketches-cpp/fi/include/frequent_items_sketch.hpp
@@ -64,7 +64,7 @@ public:
    * @param lg_start_map_size Log2 of the starting physical size of the internal hash
    * map managed by this sketch.
    */
-  explicit frequent_items_sketch(uint8_t lg_max_map_size, uint8_t lg_start_map_size = LG_MIN_MAP_SIZE, const A& allocator = A());
+  explicit frequent_items_sketch(uint8_t lg_max_map_size, size_t hashset_addr, uint8_t lg_start_map_size = LG_MIN_MAP_SIZE, const A& allocator = A());
 
   /**
    * Update this sketch with an item and a positive weight (frequency count).
@@ -271,6 +271,9 @@ public:
    */
   string<A> to_string(bool print_items = false) const;
 
+  void set_weights(W total_weight, W offset) { this->total_weight = total_weight; this->offset = offset; }
+  W get_offset() const { return this->offset; }
+
 private:
   static const uint8_t SERIAL_VERSION = 1;
   static const uint8_t FAMILY_ID = 10;
diff --git a/datasketches-cpp/fi/include/frequent_items_sketch_impl.hpp b/datasketches-cpp/fi/include/frequent_items_sketch_impl.hpp
index 593aa03..07d9ecf 100644
--- a/datasketches-cpp/fi/include/frequent_items_sketch_impl.hpp
+++ b/datasketches-cpp/fi/include/frequent_items_sketch_impl.hpp
@@ -33,11 +33,12 @@ template<typename T, typename W, typename H, typename E, typename S, typename A>
 const uint8_t frequent_items_sketch<T, W, H, E, S, A>::LG_MIN_MAP_SIZE;
 
 template<typename T, typename W, typename H, typename E, typename S, typename A>
-frequent_items_sketch<T, W, H, E, S, A>::frequent_items_sketch(uint8_t lg_max_map_size, uint8_t lg_start_map_size, const A& allocator):
+frequent_items_sketch<T, W, H, E, S, A>::frequent_items_sketch(uint8_t lg_max_map_size, size_t hashset_addr, uint8_t lg_start_map_size, const A& allocator):
 total_weight(0),
 offset(0),
 map(
   std::max(lg_start_map_size, frequent_items_sketch::LG_MIN_MAP_SIZE),
+  hashset_addr,
   std::max(lg_max_map_size, frequent_items_sketch::LG_MIN_MAP_SIZE),
   allocator
 )
@@ -321,7 +322,7 @@ frequent_items_sketch<T, W, H, E, S, A> frequent_items_sketch<T, W, H, E, S, A>:
     sketch.offset = offset;
   }
   if (!is.good())
-    throw std::runtime_error("error reading from std::istream"); 
+    throw std::runtime_error("error reading from std::istream");
   return sketch;
 }
 
diff --git a/datasketches-cpp/fi/include/reverse_purge_hash_map.hpp b/datasketches-cpp/fi/include/reverse_purge_hash_map.hpp
index fc4cd83..c667271 100644
--- a/datasketches-cpp/fi/include/reverse_purge_hash_map.hpp
+++ b/datasketches-cpp/fi/include/reverse_purge_hash_map.hpp
@@ -39,7 +39,7 @@ public:
   using AllocV = typename std::allocator_traits<A>::template rebind_alloc<V>;
   using AllocU16 = typename std::allocator_traits<A>::template rebind_alloc<uint16_t>;
 
-  reverse_purge_hash_map(uint8_t lg_size, uint8_t lg_max_size, const A& allocator);
+  reverse_purge_hash_map(uint8_t lg_size, size_t hashset_addr, uint8_t lg_max_size, const A& allocator);
   reverse_purge_hash_map(const reverse_purge_hash_map& other);
   reverse_purge_hash_map(reverse_purge_hash_map&& other) noexcept;
   ~reverse_purge_hash_map();
@@ -66,6 +66,7 @@ private:
   static constexpr uint32_t MAX_SAMPLE_SIZE = 1024; // number of samples to compute approximate median during purge
 
   A allocator_;
+  size_t hashset_addr_;
   uint8_t lg_cur_size_;
   uint8_t lg_max_size_;
   uint32_t num_active_;
diff --git a/datasketches-cpp/fi/include/reverse_purge_hash_map_impl.hpp b/datasketches-cpp/fi/include/reverse_purge_hash_map_impl.hpp
index 0b05d89..eeb0158 100644
--- a/datasketches-cpp/fi/include/reverse_purge_hash_map_impl.hpp
+++ b/datasketches-cpp/fi/include/reverse_purge_hash_map_impl.hpp
@@ -27,6 +27,8 @@
 
 #include "MurmurHash3.h"
 
+void remove_from_hashset(size_t,size_t) noexcept;
+
 namespace datasketches {
 
 // clang++ seems to require this declaration for CMAKE_BUILD_TYPE='Debug"
@@ -34,8 +36,9 @@ template<typename K, typename V, typename H, typename E, typename A>
 constexpr uint32_t reverse_purge_hash_map<K, V, H, E, A>::MAX_SAMPLE_SIZE;
 
 template<typename K, typename V, typename H, typename E, typename A>
-reverse_purge_hash_map<K, V, H, E, A>::reverse_purge_hash_map(uint8_t lg_cur_size, uint8_t lg_max_size, const A& allocator):
+reverse_purge_hash_map<K, V, H, E, A>::reverse_purge_hash_map(uint8_t lg_cur_size, uintptr_t hashset_addr, uint8_t lg_max_size, const A& allocator):
 allocator_(allocator),
+hashset_addr_(hashset_addr),
 lg_cur_size_(lg_cur_size),
 lg_max_size_(lg_max_size),
 num_active_(0),
@@ -53,6 +56,7 @@ states_(nullptr)
 template<typename K, typename V, typename H, typename E, typename A>
 reverse_purge_hash_map<K, V, H, E, A>::reverse_purge_hash_map(const reverse_purge_hash_map<K, V, H, E, A>& other):
 allocator_(other.allocator_),
+hashset_addr_(other.hashset_addr_),
 lg_cur_size_(other.lg_cur_size_),
 lg_max_size_(other.lg_max_size_),
 num_active_(other.num_active_),
@@ -81,6 +85,7 @@ states_(nullptr)
 template<typename K, typename V, typename H, typename E, typename A>
 reverse_purge_hash_map<K, V, H, E, A>::reverse_purge_hash_map(reverse_purge_hash_map<K, V, H, E, A>&& other) noexcept:
 allocator_(std::move(other.allocator_)),
+hashset_addr_(other.hashset_addr_),
 lg_cur_size_(other.lg_cur_size_),
 lg_max_size_(other.lg_max_size_),
 num_active_(other.num_active_),
@@ -245,6 +250,7 @@ void reverse_purge_hash_map<K, V, H, E, A>::hash_delete(uint32_t delete_index) {
   // item to move to this location
   // if none are found, the status is changed
   states_[delete_index] = 0; // mark as empty
+  remove_from_hashset(hashset_addr_, keys_[delete_index]);
   keys_[delete_index].~K();
   uint16_t drift = 1;
   const uint32_t mask = (1 << lg_cur_size_) - 1;