From f7bed1b8774162cd70f07540dda9c241f7f8007a Mon Sep 17 00:00:00 2001
From: Douglas Rumbaugh <dbr4@psu.edu>
Date: Mon, 5 Jun 2023 09:50:55 -0400
Subject: WSS.h: initial WSS shard implementation

---
 include/shard/WSS.h | 392 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 392 insertions(+)
 create mode 100644 include/shard/WSS.h

(limited to 'include')

diff --git a/include/shard/WSS.h b/include/shard/WSS.h
new file mode 100644
index 0000000..929f9df
--- /dev/null
+++ b/include/shard/WSS.h
@@ -0,0 +1,392 @@
+/*
+    {s.get_tombstone_count()} -> std::convertible_to<size_t>;
+ * include/shard/WSS.h
+ *
+ * Copyright (C) 2023 Dong Xie <dongx@psu.edu>
+ *
+ * All rights reserved. Published under the Modified BSD License.
+ *
+ */
+#pragma once
+
+
+#include <vector>
+#include <cassert>
+#include <queue>
+#include <memory>
+#include <concepts>
+
+#include "ds/PriorityQueue.h"
+#include "util/Cursor.h"
+#include "ds/Alias.h"
+#include "ds/BloomFilter.h"
+#include "util/bf_config.h"
+#include "framework/MutableBuffer.h"
+#include "framework/RecordInterface.h"
+#include "framework/ShardInterface.h"
+#include "framework/QueryInterface.h"
+
+namespace de {
+
+thread_local size_t wss_cancelations = 0;
+
+template <WeightedRecordInterface R>
+struct wss_query_parms {
+    size_t sample_size;
+    gsl_rng *rng;
+};
+
+template <WeightedRecordInterface R, bool Rejection>
+class WSSQuery;
+
+template <WeightedRecordInterface R>
+struct WSSState {
+    decltype(R::weight) tot_weight;
+
+    WSSState() {
+        tot_weight = 0;
+    }
+};
+
+template <WeightedRecordInterface R>
+struct WSSBufferState {
+    size_t cutoff;
+    Alias* alias;
+    decltype(R::weight) max_weight;
+
+    ~WSSBufferState() {
+        delete alias;
+    }
+
+};
+
+template <WeightedRecordInterface R>
+class WSS {
+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 WSSQuery<R, true>;
+    friend class WSSQuery<R, false>;
+
+    WSS(MutableBuffer<R>* buffer)
+    : m_reccnt(0), m_tombstone_cnt(0), m_total_weight(0) {
+
+        size_t alloc_size = (buffer->get_record_count() * sizeof(Wrapped<R>)) + (CACHELINE_SIZE - (buffer->get_record_count() * sizeof(Wrapped<R>)) % CACHELINE_SIZE);
+        assert(alloc_size % CACHELINE_SIZE == 0);
+        m_data = (Wrapped<R>*)std::aligned_alloc(CACHELINE_SIZE, alloc_size);
+
+        m_bf = new BloomFilter<K>(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>>());
+
+        std::vector<W> weights;
+
+        while (base < stop) {
+            if (!(base->is_tombstone()) && (base + 1) < stop) {
+                if (base->rec == (base + 1)->rec && (base + 1)->is_tombstone()) {
+                    base += 2;
+                    wss_cancelations++;
+                    continue;
+                }
+            } else if (base->is_deleted()) {
+                base += 1;
+                continue;
+            }
+
+            base->header &= 1;
+            m_data[m_reccnt++] = *base;
+            m_total_weight+= base->rec.weight;
+            weights.push_back(base->rec.weight);
+
+            if (m_bf && base->is_tombstone()) {
+                m_tombstone_cnt++;
+                m_bf->insert(base->rec.key);
+            }
+            
+            base++;
+        }
+
+        if (m_reccnt > 0) {
+            build_alias_structure();
+        }
+    }
+
+    WSS(WSS** shards, size_t len)
+    : m_reccnt(0), m_tombstone_cnt(0), m_total_weight(0) {
+        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<K>(BF_FPR, tombstone_count, BF_HASH_FUNCS);
+
+        size_t alloc_size = (attemp_reccnt * sizeof(Wrapped<R>)) + (CACHELINE_SIZE - (attemp_reccnt * sizeof(Wrapped<R>)) % CACHELINE_SIZE);
+        assert(alloc_size % CACHELINE_SIZE == 0);
+        m_data = (Wrapped<R>*)std::aligned_alloc(CACHELINE_SIZE, alloc_size);
+
+        std::vector<W> weights;
+        
+        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;
+                    weights.push_back(cursor.ptr->rec.weight);
+                    if (m_bf && cursor.ptr->is_tombstone()) {
+                        ++m_tombstone_cnt;
+                        if (m_bf) m_bf->insert(cursor.ptr->rec.key);
+                    }
+                }
+                pq.pop();
+                
+                if (advance_cursor<Wrapped<R>>(cursor)) pq.push(cursor.ptr, now.version);
+            }
+        }
+
+        if (m_reccnt > 0) {
+            build_alias_structure(weights);
+        }
+   }
+
+    ~WSS() {
+        if (m_data) free(m_data);
+        if (m_alias) free(m_alias);
+        if (m_bf) delete m_bf;
+
+    }
+
+    Wrapped<R> *point_lookup(const R &rec, bool filter=false) {
+        if (filter && !m_bf->lookup(rec.key)) {
+            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 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;
+    }
+
+    void build_alias_structure(std::vector<W> &weights) {
+        // normalize the weights vector
+        for (size_t i=0; i<weights.size(); i++) {
+            weights[i] = weights[i] / (double) m_total_weight;
+        }
+
+        // build the alias structure
+        m_alias = new Alias(weights);
+    }
+
+    Wrapped<R>* m_data;
+    Alias *m_alias;
+    W m_total_weight;
+    size_t m_reccnt;
+    size_t m_tombstone_cnt;
+    size_t m_group_size;
+    BloomFilter<K> *m_bf;
+};
+
+
+template <WeightedRecordInterface R, bool Rejection=true>
+class WSSQuery {
+public:
+    static void *get_query_state(WSS<R> *wss, void *parms) {
+        auto res = new WSSState<R>();
+
+        return res;
+    }
+
+    static void* get_buffer_query_state(MutableBuffer<R> *buffer, void *parms) {
+        WSSBufferState<R> *state = new WSSBufferState<R>();
+        auto parameters = (wss_query_parms<R>*) parms;
+        if constexpr (Rejection) {
+            state->cutoff = buffer->get_record_count() - 1;
+            state->max_weight = buffer->get_max_weight();
+            return state;
+        }
+
+        std::vector<double> weights;
+
+        state->cutoff = buffer->get_record_count() - 1;
+        double tot_weight = 0.0;
+
+        for (size_t i = 0; i <= state->cutoff; i++) {
+            auto rec = buffer->get_data() + i;
+            weights.push_back(rec->rec.weight);
+            state->records.push_back(*rec);
+            tot_weight += rec->rec.weight;
+        }
+
+        for (size_t i = 0; i < weights.size(); i++) {
+            weights[i] = weights[i] / tot_weight;
+        }
+
+        state->alias = new Alias(weights);
+
+        return state;
+    }
+
+    static std::vector<Wrapped<R>> query(WSS<R> *wss, void *q_state, void *parms) { 
+        auto sample_sz = ((wss_query_parms<R> *) parms)->sample_size;
+        auto rng = ((wss_query_parms<R> *) parms)->rng;
+
+        auto state = (WSSState<R> *) q_state;
+
+        std::vector<Wrapped<R>> result_set;
+
+        if (sample_sz == 0) {
+            return result_set;
+        }
+        size_t attempts = 0;
+        do {
+            attempts++;
+            size_t idx = wss->m_alias->get(rng);
+            result_set.emplace_back(*wss->get_record_at(idx));
+        } while (attempts < sample_sz);
+
+        return result_set;
+    }
+
+    static std::vector<Wrapped<R>> buffer_query(MutableBuffer<R> *buffer, void *state, void *parms) {
+        auto st = (WSSBufferState<R> *) state;
+        auto p = (wss_query_parms<R> *) parms;
+
+        std::vector<Wrapped<R>> result;
+        result.reserve(p->sample_size);
+
+        if constexpr (Rejection) {
+            for (size_t i=0; i<p->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) {
+                    result.emplace_back(*rec);
+                }
+            }
+            return result;
+        }
+
+        for (size_t i=0; i<p->sample_size; i++) {
+            auto idx = st->alias->get(p->rng);
+            result.emplace_back(*(buffer->get_data() + idx));
+        }
+
+        return result;
+    }
+
+    static std::vector<R> merge(std::vector<std::vector<R>> &results) {
+        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]);
+            }
+        }
+
+        return output;
+    }
+
+    static void delete_query_state(void *state) {
+        auto s = (WSSState<R> *) state;
+        delete s;
+    }
+
+    static void delete_buffer_query_state(void *state) {
+        auto s = (WSSBufferState<R> *) state;
+        delete s;
+    }
+
+
+    //{q.get_buffer_query_state(p, p)};
+    //{q.buffer_query(p, p)};
+
+};
+
+}
-- 
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