From 9e1c1b1b930031896851b1ed4a15152508327d73 Mon Sep 17 00:00:00 2001
From: Douglas Rumbaugh <dbr4@psu.edu>
Date: Tue, 7 Nov 2023 13:35:54 -0500
Subject: Converted WIRS to the new interface

---
 include/shard/AugBTree.h | 371 +++++++++++++++++++++++++++++
 include/shard/WIRS.h     | 594 -----------------------------------------------
 2 files changed, 371 insertions(+), 594 deletions(-)
 create mode 100644 include/shard/AugBTree.h
 delete mode 100644 include/shard/WIRS.h

(limited to 'include/shard')

diff --git a/include/shard/AugBTree.h b/include/shard/AugBTree.h
new file mode 100644
index 0000000..e32ec64
--- /dev/null
+++ b/include/shard/AugBTree.h
@@ -0,0 +1,371 @@
+/*
+ * include/shard/AugBTree.h
+ *
+ * Copyright (C) 2023 Dong Xie <dongx@psu.edu>
+ *                    Douglas B. Rumbaugh <drumbaugh@psu.edu>
+ *
+ * All rights reserved. Published under the Modified BSD License.
+ *
+ */
+#pragma once
+
+
+#include <vector>
+#include <cassert>
+#include <queue>
+#include <memory>
+#include <concepts>
+
+#include "framework/ShardRequirements.h"
+
+#include "psu-ds/PriorityQueue.h"
+#include "util/Cursor.h"
+#include "psu-ds/Alias.h"
+#include "psu-ds/BloomFilter.h"
+#include "util/bf_config.h"
+
+using psudb::CACHELINE_SIZE;
+using psudb::BloomFilter;
+using psudb::PriorityQueue;
+using psudb::queue_record;
+using psudb::Alias;
+
+namespace de {
+
+thread_local size_t wirs_cancelations = 0;
+
+template <WeightedRecordInterface R>
+struct AugBTreeNode {
+    struct AugBTreeNode<R> *left, *right;
+    decltype(R::key) low, high;
+    decltype(R::weight) weight;
+    Alias* alias;
+};
+
+template <WeightedRecordInterface R>
+class AugBTree {
+private:
+    typedef decltype(R::key) K;
+    typedef decltype(R::value) V;
+    typedef decltype(R::weight) W;
+
+public:
+    AugBTree(MutableBuffer<R>* buffer)
+    : m_reccnt(0), m_tombstone_cnt(0), m_total_weight(0), m_root(nullptr) {
+        m_alloc_size = (buffer->get_record_count() * sizeof(Wrapped<R>)) + (CACHELINE_SIZE - (buffer->get_record_count() * sizeof(Wrapped<R>)) % CACHELINE_SIZE);
+        assert(m_alloc_size % CACHELINE_SIZE == 0);
+        m_data = (Wrapped<R>*)std::aligned_alloc(CACHELINE_SIZE, m_alloc_size);
+
+        m_bf = new BloomFilter<R>(BF_FPR, buffer->get_tombstone_count(), BF_HASH_FUNCS);
+
+        size_t offset = 0;
+        m_reccnt = 0;
+        auto base = buffer->get_data();
+        auto stop = base + buffer->get_record_count();
+
+        std::sort(base, stop, std::less<Wrapped<R>>());
+
+        while (base < stop) {
+            if (!(base->is_tombstone()) && (base + 1) < stop) {
+                if (base->rec == (base + 1)->rec && (base + 1)->is_tombstone()) {
+                    base += 2;
+                    wirs_cancelations++;
+                    continue;
+                }
+            } else if (base->is_deleted()) {
+                base += 1;
+                continue;
+            }
+
+            // FIXME: this shouldn't be necessary, but the tagged record
+            // bypass doesn't seem to be working on this code-path, so this
+            // ensures that tagged records from the buffer are able to be
+            // dropped, eventually. It should only need to be &= 1
+            base->header &= 3;
+            m_data[m_reccnt++] = *base;
+            m_total_weight+= base->rec.weight;
+
+            if (m_bf && base->is_tombstone()) {
+                m_tombstone_cnt++;
+                m_bf->insert(base->rec);
+            }
+            
+            base++;
+        }
+
+        if (m_reccnt > 0) {
+            build_wirs_structure();
+        }
+    }
+
+    AugBTree(AugBTree** shards, size_t len)
+    : m_reccnt(0), m_tombstone_cnt(0), m_total_weight(0), m_root(nullptr) {
+        std::vector<Cursor<Wrapped<R>>> cursors;
+        cursors.reserve(len);
+
+        PriorityQueue<Wrapped<R>> pq(len);
+
+        size_t attemp_reccnt = 0;
+        size_t tombstone_count = 0;
+        
+        for (size_t i = 0; i < len; ++i) {
+            if (shards[i]) {
+                auto base = shards[i]->get_data();
+                cursors.emplace_back(Cursor{base, base + shards[i]->get_record_count(), 0, shards[i]->get_record_count()});
+                attemp_reccnt += shards[i]->get_record_count();
+                tombstone_count += shards[i]->get_tombstone_count();
+                pq.push(cursors[i].ptr, i);
+            } else {
+                cursors.emplace_back(Cursor<Wrapped<R>>{nullptr, nullptr, 0, 0});
+            }
+        }
+
+        m_bf = new BloomFilter<R>(BF_FPR, tombstone_count, BF_HASH_FUNCS);
+
+        m_alloc_size = (attemp_reccnt * sizeof(Wrapped<R>)) + (CACHELINE_SIZE - (attemp_reccnt * sizeof(Wrapped<R>)) % CACHELINE_SIZE);
+        assert(m_alloc_size % CACHELINE_SIZE == 0);
+        m_data = (Wrapped<R>*)std::aligned_alloc(CACHELINE_SIZE, m_alloc_size);
+        
+        while (pq.size()) {
+            auto now = pq.peek();
+            auto next = pq.size() > 1 ? pq.peek(1) : queue_record<Wrapped<R>>{nullptr, 0};
+            if (!now.data->is_tombstone() && next.data != nullptr &&
+                now.data->rec == next.data->rec && next.data->is_tombstone()) {
+                
+                pq.pop(); pq.pop();
+                auto& cursor1 = cursors[now.version];
+                auto& cursor2 = cursors[next.version];
+                if (advance_cursor<Wrapped<R>>(cursor1)) pq.push(cursor1.ptr, now.version);
+                if (advance_cursor<Wrapped<R>>(cursor2)) pq.push(cursor2.ptr, next.version);
+            } else {
+                auto& cursor = cursors[now.version];
+                if (!cursor.ptr->is_deleted()) {
+                    m_data[m_reccnt++] = *cursor.ptr;
+                    m_total_weight += cursor.ptr->rec.weight;
+                    if (m_bf && cursor.ptr->is_tombstone()) {
+                        ++m_tombstone_cnt;
+                        if (m_bf) m_bf->insert(cursor.ptr->rec);
+                    }
+                }
+                pq.pop();
+                
+                if (advance_cursor<Wrapped<R>>(cursor)) pq.push(cursor.ptr, now.version);
+            }
+        }
+
+        if (m_reccnt > 0) {
+            build_wirs_structure();
+        }
+   }
+
+    ~AugBTree() {
+        if (m_data) free(m_data);
+        for (size_t i=0; i<m_alias.size(); i++) {
+            if (m_alias[i]) delete m_alias[i];
+        }
+
+        if (m_bf) delete m_bf;
+
+        free_tree(m_root);
+    }
+
+    Wrapped<R> *point_lookup(const R &rec, bool filter=false) {
+        if (filter && !m_bf->lookup(rec)) {
+            return nullptr;
+        }
+
+        size_t idx = get_lower_bound(rec.key);
+        if (idx >= m_reccnt) {
+            return nullptr;
+        }
+
+        while (idx < m_reccnt && m_data[idx].rec < rec) ++idx;
+
+        if (m_data[idx].rec == rec) {
+            return m_data + idx;
+        }
+
+        return nullptr;
+    }
+
+    Wrapped<R>* get_data() const {
+        return m_data;
+    }
+    
+    size_t get_record_count() const {
+        return m_reccnt;
+    }
+
+    size_t get_tombstone_count() const {
+        return m_tombstone_cnt;
+    }
+
+    const Wrapped<R>* get_record_at(size_t idx) const {
+        if (idx >= m_reccnt) return nullptr;
+        return m_data + idx;
+    }
+
+
+    size_t get_memory_usage() {
+        return m_alloc_size + m_node_cnt * sizeof(AugBTreeNode<Wrapped<R>>);
+    }
+
+    size_t get_aux_memory_usage() {
+        return 0;
+    }
+
+    size_t get_lower_bound(const K& key) const {
+        size_t min = 0;
+        size_t max = m_reccnt - 1;
+
+        const char * record_key;
+        while (min < max) {
+            size_t mid = (min + max) / 2;
+
+            if (key > m_data[mid].rec.key) {
+                min = mid + 1;
+            } else {
+                max = mid;
+            }
+        }
+
+        return min;
+    }
+
+    W find_covering_nodes(K lower_key, K upper_key, std::vector<void *> &nodes, std::vector<W> &weights) {
+        W total_weight = 0;
+        
+        /* Simulate a stack to unfold recursion. */       
+        struct AugBTreeNode<R>* st[64] = {0};
+        st[0] = m_root;
+        size_t top = 1;
+        while(top > 0) {
+            auto now = st[--top];
+            if (covered_by(now, lower_key, upper_key) ||
+                (now->left == nullptr && now->right == nullptr && intersects(now, lower_key, upper_key))) {
+                nodes.emplace_back(now);
+                weights.emplace_back(now->weight);
+                total_weight += now->weight;
+            } else {
+                if (now->left && intersects(now->left, lower_key, upper_key)) st[top++] = now->left;
+                if (now->right && intersects(now->right, lower_key, upper_key)) st[top++] = now->right;
+            }
+        }
+        
+
+        return total_weight;
+    }
+
+    Wrapped<R> *get_weighted_sample(K lower_key, K upper_key, void *internal_node, gsl_rng *rng) {
+        /* k -> sampling: three levels. 1. select a node -> select a fat point -> select a record. */
+
+        /* first level */ 
+        auto node = (AugBTreeNode<R>*) internal_node;
+
+        /* second level */
+        auto fat_point = node->low + node->alias->get(rng);
+
+        /* third level */
+        size_t rec_offset = fat_point * m_group_size + m_alias[fat_point]->get(rng);
+        auto record = m_data + rec_offset;
+
+        /* bounds rejection */
+        if (lower_key > record->rec.key || upper_key < record->rec.key) {
+            return nullptr;
+        } 
+
+        return record;
+    }
+
+private:
+
+    bool covered_by(struct AugBTreeNode<R>* node, const K& lower_key, const K& upper_key) {
+        auto low_index = node->low * m_group_size;
+        auto high_index = std::min((node->high + 1) * m_group_size - 1, m_reccnt - 1);
+        return lower_key < m_data[low_index].rec.key && m_data[high_index].rec.key < upper_key;
+    }
+
+    bool intersects(struct AugBTreeNode<R>* node, const K& lower_key, const K& upper_key) {
+        auto low_index = node->low * m_group_size;
+        auto high_index = std::min((node->high + 1) * m_group_size - 1, m_reccnt - 1);
+        return lower_key < m_data[high_index].rec.key && m_data[low_index].rec.key < upper_key;
+    }
+
+    void build_wirs_structure() {
+        m_group_size = std::ceil(std::log(m_reccnt));
+        size_t n_groups = std::ceil((double) m_reccnt / (double) m_group_size);
+        
+        // Fat point construction + low level alias....
+        double sum_weight = 0.0;
+        std::vector<W> weights;
+        std::vector<double> group_norm_weight;
+        size_t i = 0;
+        size_t group_no = 0;
+        while (i < m_reccnt) {
+            double group_weight = 0.0;
+            group_norm_weight.clear();
+            for (size_t k = 0; k < m_group_size && i < m_reccnt; ++k, ++i) {
+                auto w = m_data[i].rec.weight;
+                group_norm_weight.emplace_back(w);
+                group_weight += w;
+                sum_weight += w;
+            }
+
+            for (auto& w: group_norm_weight)
+                if (group_weight) w /= group_weight;
+                else w = 1.0 / group_norm_weight.size();
+            m_alias.emplace_back(new Alias(group_norm_weight));
+
+            
+            weights.emplace_back(group_weight);
+        }
+
+        assert(weights.size() == n_groups);
+
+        m_root = construct_AugBTreeNode(weights, 0, n_groups-1);
+    }
+
+     struct AugBTreeNode<R>* construct_AugBTreeNode(const std::vector<W>& weights, size_t low, size_t high) {
+        if (low == high) {
+            return new AugBTreeNode<R>{nullptr, nullptr, low, high, weights[low], new Alias({1.0})};
+        } else if (low > high) return nullptr;
+
+        std::vector<double> node_weights;
+        W sum = 0;
+        for (size_t i = low; i < high; ++i) {
+            node_weights.emplace_back(weights[i]);
+            sum += weights[i];
+        }
+
+        for (auto& w: node_weights)
+            if (sum) w /= sum;
+            else w = 1.0 / node_weights.size();
+        
+        m_node_cnt += 1; 
+        size_t mid = (low + high) / 2;
+        return new AugBTreeNode<R>{construct_AugBTreeNode(weights, low, mid),
+                                construct_AugBTreeNode(weights, mid + 1, high),
+                                low, high, sum, new Alias(node_weights)};
+    }
+
+    void free_tree(struct AugBTreeNode<R>* node) {
+        if (node) {
+            delete node->alias;
+            free_tree(node->left);
+            free_tree(node->right);
+            delete node;
+        }
+    }
+
+    Wrapped<R>* m_data;
+    std::vector<Alias *> m_alias;
+    AugBTreeNode<R>* m_root;
+    W m_total_weight;
+    size_t m_reccnt;
+    size_t m_tombstone_cnt;
+    size_t m_group_size;
+    size_t m_alloc_size;
+    size_t m_node_cnt;
+    BloomFilter<R> *m_bf;
+};
+}
diff --git a/include/shard/WIRS.h b/include/shard/WIRS.h
deleted file mode 100644
index bf29325..0000000
--- a/include/shard/WIRS.h
+++ /dev/null
@@ -1,594 +0,0 @@
-/*
- * include/shard/WIRS.h
- *
- * Copyright (C) 2023 Dong Xie <dongx@psu.edu>
- *                    Douglas B. Rumbaugh <drumbaugh@psu.edu>
- *
- * All rights reserved. Published under the Modified BSD License.
- *
- */
-#pragma once
-
-
-#include <vector>
-#include <cassert>
-#include <queue>
-#include <memory>
-#include <concepts>
-
-#include "framework/ShardRequirements.h"
-
-#include "psu-ds/PriorityQueue.h"
-#include "util/Cursor.h"
-#include "psu-ds/Alias.h"
-#include "psu-ds/BloomFilter.h"
-#include "util/bf_config.h"
-
-using psudb::CACHELINE_SIZE;
-using psudb::BloomFilter;
-using psudb::PriorityQueue;
-using psudb::queue_record;
-using psudb::Alias;
-
-namespace de {
-
-thread_local size_t wirs_cancelations = 0;
-
-template <WeightedRecordInterface R>
-struct wirs_query_parms {
-    decltype(R::key) lower_bound;
-    decltype(R::key) upper_bound;
-    size_t sample_size;
-    gsl_rng *rng;
-};
-
-template <WeightedRecordInterface R, bool Rejection>
-class WIRSQuery;
-
-template <WeightedRecordInterface R>
-struct wirs_node {
-    struct wirs_node<R> *left, *right;
-    decltype(R::key) low, high;
-    decltype(R::weight) weight;
-    Alias* alias;
-};
-
-template <WeightedRecordInterface R>
-struct WIRSState {
-    decltype(R::weight) total_weight;
-    std::vector<wirs_node<R>*> nodes;
-    Alias* top_level_alias;
-    size_t sample_size;
-
-    WIRSState() {
-        total_weight = 0;
-        top_level_alias = nullptr;
-    }
-
-    ~WIRSState() {
-        if (top_level_alias) delete top_level_alias;
-    }
-};
-
-template <WeightedRecordInterface R>
-struct WIRSBufferState {
-    size_t cutoff;
-    Alias* alias;
-    std::vector<Wrapped<R>> records;
-    decltype(R::weight) max_weight;
-    size_t sample_size;
-    decltype(R::weight) total_weight;
-
-    ~WIRSBufferState() {
-        delete alias;
-    }
-
-};
-
-template <WeightedRecordInterface R>
-class WIRS {
-private:
-
-    typedef decltype(R::key) K;
-    typedef decltype(R::value) V;
-    typedef decltype(R::weight) W;
-
-public:
-
-    // FIXME: there has to be a better way to do this
-    friend class WIRSQuery<R, true>;
-    friend class WIRSQuery<R, false>;
-
-    WIRS(MutableBuffer<R>* buffer)
-    : m_reccnt(0), m_tombstone_cnt(0), m_total_weight(0), m_root(nullptr) {
-
-        m_alloc_size = (buffer->get_record_count() * sizeof(Wrapped<R>)) + (CACHELINE_SIZE - (buffer->get_record_count() * sizeof(Wrapped<R>)) % CACHELINE_SIZE);
-        assert(m_alloc_size % CACHELINE_SIZE == 0);
-        m_data = (Wrapped<R>*)std::aligned_alloc(CACHELINE_SIZE, m_alloc_size);
-
-        m_bf = new BloomFilter<R>(BF_FPR, buffer->get_tombstone_count(), BF_HASH_FUNCS);
-
-        size_t offset = 0;
-        m_reccnt = 0;
-        auto base = buffer->get_data();
-        auto stop = base + buffer->get_record_count();
-
-        std::sort(base, stop, std::less<Wrapped<R>>());
-
-        while (base < stop) {
-            if (!(base->is_tombstone()) && (base + 1) < stop) {
-                if (base->rec == (base + 1)->rec && (base + 1)->is_tombstone()) {
-                    base += 2;
-                    wirs_cancelations++;
-                    continue;
-                }
-            } else if (base->is_deleted()) {
-                base += 1;
-                continue;
-            }
-
-            // FIXME: this shouldn't be necessary, but the tagged record
-            // bypass doesn't seem to be working on this code-path, so this
-            // ensures that tagged records from the buffer are able to be
-            // dropped, eventually. It should only need to be &= 1
-            base->header &= 3;
-            m_data[m_reccnt++] = *base;
-            m_total_weight+= base->rec.weight;
-
-            if (m_bf && base->is_tombstone()) {
-                m_tombstone_cnt++;
-                m_bf->insert(base->rec);
-            }
-            
-            base++;
-        }
-
-        if (m_reccnt > 0) {
-            build_wirs_structure();
-        }
-    }
-
-    WIRS(WIRS** shards, size_t len)
-    : m_reccnt(0), m_tombstone_cnt(0), m_total_weight(0), m_root(nullptr) {
-        std::vector<Cursor<Wrapped<R>>> cursors;
-        cursors.reserve(len);
-
-        PriorityQueue<Wrapped<R>> pq(len);
-
-        size_t attemp_reccnt = 0;
-        size_t tombstone_count = 0;
-        
-        for (size_t i = 0; i < len; ++i) {
-            if (shards[i]) {
-                auto base = shards[i]->get_data();
-                cursors.emplace_back(Cursor{base, base + shards[i]->get_record_count(), 0, shards[i]->get_record_count()});
-                attemp_reccnt += shards[i]->get_record_count();
-                tombstone_count += shards[i]->get_tombstone_count();
-                pq.push(cursors[i].ptr, i);
-            } else {
-                cursors.emplace_back(Cursor<Wrapped<R>>{nullptr, nullptr, 0, 0});
-            }
-        }
-
-        m_bf = new BloomFilter<R>(BF_FPR, tombstone_count, BF_HASH_FUNCS);
-
-        m_alloc_size = (attemp_reccnt * sizeof(Wrapped<R>)) + (CACHELINE_SIZE - (attemp_reccnt * sizeof(Wrapped<R>)) % CACHELINE_SIZE);
-        assert(m_alloc_size % CACHELINE_SIZE == 0);
-        m_data = (Wrapped<R>*)std::aligned_alloc(CACHELINE_SIZE, m_alloc_size);
-        
-        while (pq.size()) {
-            auto now = pq.peek();
-            auto next = pq.size() > 1 ? pq.peek(1) : queue_record<Wrapped<R>>{nullptr, 0};
-            if (!now.data->is_tombstone() && next.data != nullptr &&
-                now.data->rec == next.data->rec && next.data->is_tombstone()) {
-                
-                pq.pop(); pq.pop();
-                auto& cursor1 = cursors[now.version];
-                auto& cursor2 = cursors[next.version];
-                if (advance_cursor<Wrapped<R>>(cursor1)) pq.push(cursor1.ptr, now.version);
-                if (advance_cursor<Wrapped<R>>(cursor2)) pq.push(cursor2.ptr, next.version);
-            } else {
-                auto& cursor = cursors[now.version];
-                if (!cursor.ptr->is_deleted()) {
-                    m_data[m_reccnt++] = *cursor.ptr;
-                    m_total_weight += cursor.ptr->rec.weight;
-                    if (m_bf && cursor.ptr->is_tombstone()) {
-                        ++m_tombstone_cnt;
-                        if (m_bf) m_bf->insert(cursor.ptr->rec);
-                    }
-                }
-                pq.pop();
-                
-                if (advance_cursor<Wrapped<R>>(cursor)) pq.push(cursor.ptr, now.version);
-            }
-        }
-
-        if (m_reccnt > 0) {
-            build_wirs_structure();
-        }
-   }
-
-    ~WIRS() {
-        if (m_data) free(m_data);
-        for (size_t i=0; i<m_alias.size(); i++) {
-            if (m_alias[i]) delete m_alias[i];
-        }
-
-        if (m_bf) delete m_bf;
-
-        free_tree(m_root);
-    }
-
-    Wrapped<R> *point_lookup(const R &rec, bool filter=false) {
-        if (filter && !m_bf->lookup(rec)) {
-            return nullptr;
-        }
-
-        size_t idx = get_lower_bound(rec.key);
-        if (idx >= m_reccnt) {
-            return nullptr;
-        }
-
-        while (idx < m_reccnt && m_data[idx].rec < rec) ++idx;
-
-        if (m_data[idx].rec == rec) {
-            return m_data + idx;
-        }
-
-        return nullptr;
-    }
-
-    Wrapped<R>* get_data() const {
-        return m_data;
-    }
-    
-    size_t get_record_count() const {
-        return m_reccnt;
-    }
-
-    size_t get_tombstone_count() const {
-        return m_tombstone_cnt;
-    }
-
-    const Wrapped<R>* get_record_at(size_t idx) const {
-        if (idx >= m_reccnt) return nullptr;
-        return m_data + idx;
-    }
-
-
-    size_t get_memory_usage() {
-        return m_alloc_size + m_node_cnt * sizeof(wirs_node<Wrapped<R>>);
-    }
-
-    size_t get_aux_memory_usage() {
-        return 0;
-    }
-
-private:
-
-    size_t get_lower_bound(const K& key) const {
-        size_t min = 0;
-        size_t max = m_reccnt - 1;
-
-        const char * record_key;
-        while (min < max) {
-            size_t mid = (min + max) / 2;
-
-            if (key > m_data[mid].rec.key) {
-                min = mid + 1;
-            } else {
-                max = mid;
-            }
-        }
-
-        return min;
-    }
-
-    bool covered_by(struct wirs_node<R>* node, const K& lower_key, const K& upper_key) {
-        auto low_index = node->low * m_group_size;
-        auto high_index = std::min((node->high + 1) * m_group_size - 1, m_reccnt - 1);
-        return lower_key < m_data[low_index].rec.key && m_data[high_index].rec.key < upper_key;
-    }
-
-    bool intersects(struct wirs_node<R>* node, const K& lower_key, const K& upper_key) {
-        auto low_index = node->low * m_group_size;
-        auto high_index = std::min((node->high + 1) * m_group_size - 1, m_reccnt - 1);
-        return lower_key < m_data[high_index].rec.key && m_data[low_index].rec.key < upper_key;
-    }
-
-    void build_wirs_structure() {
-        m_group_size = std::ceil(std::log(m_reccnt));
-        size_t n_groups = std::ceil((double) m_reccnt / (double) m_group_size);
-        
-        // Fat point construction + low level alias....
-        double sum_weight = 0.0;
-        std::vector<W> weights;
-        std::vector<double> group_norm_weight;
-        size_t i = 0;
-        size_t group_no = 0;
-        while (i < m_reccnt) {
-            double group_weight = 0.0;
-            group_norm_weight.clear();
-            for (size_t k = 0; k < m_group_size && i < m_reccnt; ++k, ++i) {
-                auto w = m_data[i].rec.weight;
-                group_norm_weight.emplace_back(w);
-                group_weight += w;
-                sum_weight += w;
-            }
-
-            for (auto& w: group_norm_weight)
-                if (group_weight) w /= group_weight;
-                else w = 1.0 / group_norm_weight.size();
-            m_alias.emplace_back(new Alias(group_norm_weight));
-
-            
-            weights.emplace_back(group_weight);
-        }
-
-        assert(weights.size() == n_groups);
-
-        m_root = construct_wirs_node(weights, 0, n_groups-1);
-    }
-
-     struct wirs_node<R>* construct_wirs_node(const std::vector<W>& weights, size_t low, size_t high) {
-        if (low == high) {
-            return new wirs_node<R>{nullptr, nullptr, low, high, weights[low], new Alias({1.0})};
-        } else if (low > high) return nullptr;
-
-        std::vector<double> node_weights;
-        W sum = 0;
-        for (size_t i = low; i < high; ++i) {
-            node_weights.emplace_back(weights[i]);
-            sum += weights[i];
-        }
-
-        for (auto& w: node_weights)
-            if (sum) w /= sum;
-            else w = 1.0 / node_weights.size();
-        
-        m_node_cnt += 1; 
-        size_t mid = (low + high) / 2;
-        return new wirs_node<R>{construct_wirs_node(weights, low, mid),
-                                construct_wirs_node(weights, mid + 1, high),
-                                low, high, sum, new Alias(node_weights)};
-    }
-
-    void free_tree(struct wirs_node<R>* node) {
-        if (node) {
-            delete node->alias;
-            free_tree(node->left);
-            free_tree(node->right);
-            delete node;
-        }
-    }
-
-    Wrapped<R>* m_data;
-    std::vector<Alias *> m_alias;
-    wirs_node<R>* m_root;
-    W m_total_weight;
-    size_t m_reccnt;
-    size_t m_tombstone_cnt;
-    size_t m_group_size;
-    size_t m_alloc_size;
-    size_t m_node_cnt;
-    BloomFilter<R> *m_bf;
-};
-
-
-template <WeightedRecordInterface R, bool Rejection=true>
-class WIRSQuery {
-public:
-
-    constexpr static bool EARLY_ABORT=false;
-    constexpr static bool SKIP_DELETE_FILTER=false;
-
-    static void *get_query_state(WIRS<R> *wirs, void *parms) {
-        auto res = new WIRSState<R>();
-        decltype(R::key) lower_key = ((wirs_query_parms<R> *) parms)->lower_bound;
-        decltype(R::key) upper_key = ((wirs_query_parms<R> *) parms)->upper_bound;
-
-        // Simulate a stack to unfold recursion.        
-        double total_weight = 0.0;
-        struct wirs_node<R>* st[64] = {0};
-        st[0] = wirs->m_root;
-        size_t top = 1;
-        while(top > 0) {
-            auto now = st[--top];
-            if (wirs->covered_by(now, lower_key, upper_key) ||
-                (now->left == nullptr && now->right == nullptr && wirs->intersects(now, lower_key, upper_key))) {
-                res->nodes.emplace_back(now);
-                total_weight += now->weight;
-            } else {
-                if (now->left && wirs->intersects(now->left, lower_key, upper_key)) st[top++] = now->left;
-                if (now->right && wirs->intersects(now->right, lower_key, upper_key)) st[top++] = now->right;
-            }
-        }
-        
-        std::vector<double> weights;
-        for (const auto& node: res->nodes) {
-            weights.emplace_back(node->weight / total_weight);
-        }
-        res->total_weight = total_weight;
-        res->top_level_alias = new Alias(weights);
-        res->sample_size = 0;
-
-        return res;
-    }
-
-    static void* get_buffer_query_state(MutableBuffer<R> *buffer, void *parms) {
-        WIRSBufferState<R> *state = new WIRSBufferState<R>();
-        auto parameters = (wirs_query_parms<R>*) parms;
-        if constexpr (Rejection) {
-            state->cutoff = buffer->get_record_count() - 1;
-            state->max_weight = buffer->get_max_weight();
-            state->total_weight = buffer->get_total_weight();
-            state->sample_size = 0;
-            return state;
-        }
-
-        std::vector<double> weights;
-
-        state->cutoff = buffer->get_record_count() - 1;
-        double total_weight = 0.0;
-
-        for (size_t i = 0; i <= state->cutoff; i++) {
-            auto rec = buffer->get_data() + i;
-
-            if (rec->rec.key >= parameters->lower_bound && rec->rec.key <= parameters->upper_bound && !rec->is_tombstone() && !rec->is_deleted()) {
-              weights.push_back(rec->rec.weight);
-              state->records.push_back(*rec);
-              total_weight += rec->rec.weight;
-            }
-        }
-
-        for (size_t i = 0; i < weights.size(); i++) {
-            weights[i] = weights[i] / total_weight;
-        }
-
-        state->total_weight = total_weight;
-        state->alias = new Alias(weights);
-        state->sample_size = 0;
-
-        return state;
-    }
-
-    static void process_query_states(void *query_parms, std::vector<void*> &shard_states, std::vector<void*> &buff_states) {
-        // FIXME: need to redo for the buffer vector interface
-        auto p = (wirs_query_parms<R> *) query_parms;
-
-        std::vector<size_t> shard_sample_sizes(shard_states.size()+1, 0);
-        size_t buffer_sz = 0;
-
-        decltype(R::weight) total_weight = 0;
-        std::vector<decltype(R::weight)> weights;
-        for (auto &s : buff_states) {
-            auto state = (WIRSBufferState<R> *) s;
-            total_weight += state->total_weight;
-            weights.push_back(state->total_weight);
-        }
-
-        for (auto &s : shard_states) {
-            auto state = (WIRSState<R> *) s;
-            total_weight += state->total_weight;
-            weights.push_back(state->total_weight);
-        }
-
-        std::vector<double> normalized_weights;
-        for (auto w : weights) {
-            normalized_weights.push_back((double) w / (double) total_weight);
-        }
-
-        auto shard_alias = Alias(normalized_weights);
-        for (size_t i=0; i<p->sample_size; i++) {
-            auto idx = shard_alias.get(p->rng);            
-            if (idx == 0) {
-                buffer_sz++;
-            } else {
-                shard_sample_sizes[idx - 1]++;
-            }
-        }
-
-        for (size_t i=0; i<shard_states.size(); i++) {
-            auto state = (WIRSState<R> *) shard_states[i];
-            state->sample_size = shard_sample_sizes[i+1];
-        }
-    }
-
-
-
-    static std::vector<Wrapped<R>> query(WIRS<R> *wirs, void *q_state, void *parms) { 
-        auto lower_key = ((wirs_query_parms<R> *) parms)->lower_bound;
-        auto upper_key = ((wirs_query_parms<R> *) parms)->upper_bound;
-        auto rng = ((wirs_query_parms<R> *) parms)->rng;
-
-        auto state = (WIRSState<R> *) q_state;
-        auto sample_size = state->sample_size;
-
-        std::vector<Wrapped<R>> result_set;
-
-        if (sample_size == 0) {
-            return result_set;
-        }
-        // k -> sampling: three levels. 1. select a node -> select a fat point -> select a record.
-        size_t cnt = 0;
-        size_t attempts = 0;
-        do {
-            ++attempts;
-            // first level....
-            auto node = state->nodes[state->top_level_alias->get(rng)];
-            // second level...
-            auto fat_point = node->low + node->alias->get(rng);
-            // third level...
-            size_t rec_offset = fat_point * wirs->m_group_size + wirs->m_alias[fat_point]->get(rng);
-            auto record = wirs->m_data + rec_offset;
-
-            // bounds rejection
-            if (lower_key > record->rec.key || upper_key < record->rec.key) {
-                continue;
-            } 
-
-            result_set.emplace_back(*record);
-            cnt++;
-        } while (attempts < sample_size);
-
-        return result_set;
-    }
-
-    static std::vector<Wrapped<R>> buffer_query(MutableBuffer<R> *buffer, void *state, void *parms) {
-        auto st = (WIRSBufferState<R> *) state;
-        auto p = (wirs_query_parms<R> *) parms;
-
-        std::vector<Wrapped<R>> result;
-        result.reserve(st->sample_size);
-
-        if constexpr (Rejection) {
-            for (size_t i=0; i<st->sample_size; i++) {
-                auto idx = gsl_rng_uniform_int(p->rng, st->cutoff);
-                auto rec = buffer->get_data() + idx;
-
-                auto test = gsl_rng_uniform(p->rng) * st->max_weight;
-
-                if (test <= rec->rec.weight && rec->rec.key >= p->lower_bound && rec->rec.key <= p->upper_bound) {
-                    result.emplace_back(*rec);
-                }
-            }
-            return result;
-        }
-
-        for (size_t i=0; i<st->sample_size; i++) {
-            auto idx = st->alias->get(p->rng);
-            result.emplace_back(st->records[idx]);
-        }
-
-        return result;
-    }
-
-    static std::vector<R> merge(std::vector<std::vector<Wrapped<R>>> &results, void *parms) {
-        std::vector<R> output;
-
-        for (size_t i=0; i<results.size(); i++) {
-            for (size_t j=0; j<results[i].size(); j++) {
-                output.emplace_back(results[i][j].rec);
-            }
-        }
-
-        return output;
-    }
-
-    static void delete_query_state(void *state) {
-        auto s = (WIRSState<R> *) state;
-        delete s;
-    }
-
-    static void delete_buffer_query_state(void *state) {
-        auto s = (WIRSBufferState<R> *) state;
-        delete s;
-    }
-
-
-    //{q.get_buffer_query_state(p, p)};
-    //{q.buffer_query(p, p)};
-
-};
-
-}
-- 
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