compact-quotient-filter.cc

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
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*/
 
#include <gtest/gtest.h>
 
#include <quotient-filter.H>
#include <compact-quotient-filter.H>
 
#include <cstddef>
#include <string>
#include <set>
#include <random>
#include <vector>
#include <algorithm>
 
using namespace Aleph;
using namespace std;
 
// =====================================================================
// Construction
// =====================================================================
 
TEST(CompactQuotientFilterCtor, valid_parameters)
{
  Compact_Quotient_Filter<int> qf(4, 8);
  EXPECT_EQ(qf.q(), 4);
  EXPECT_EQ(qf.r(), 8);
  EXPECT_EQ(qf.capacity(), 16u);
  EXPECT_EQ(qf.size(), 0u);
  EXPECT_TRUE(qf.is_empty());
}
 
TEST(CompactQuotientFilterCtor, rejects_invalid_q)
{
  EXPECT_THROW((Compact_Quotient_Filter<int>(0, 8)), std::domain_error);
  EXPECT_THROW((Compact_Quotient_Filter<int>(33, 8)), std::domain_error);
}
 
TEST(CompactQuotientFilterCtor, rejects_invalid_r)
{
  EXPECT_THROW((Compact_Quotient_Filter<int>(4, 0)), std::domain_error);
  EXPECT_THROW((Compact_Quotient_Filter<int>(4, 61)), std::domain_error);
}
 
TEST(CompactQuotientFilterCtor, rejects_q_plus_r_exceeds_64)
{
  EXPECT_THROW((Compact_Quotient_Filter<int>(32, 33)), std::domain_error);
}
 
TEST(CompactQuotientFilterCtor, from_capacity_creates_valid_filter)
{
  auto qf = Compact_Quotient_Filter<int>::from_capacity(1000, 0.01);
  EXPECT_GE(qf.capacity(), 1000u);
  EXPECT_LE(qf.false_positive_rate(), 0.02);
}
 
TEST(CompactQuotientFilterCtor, from_capacity_rejects_bad_args)
{
  EXPECT_THROW(Compact_Quotient_Filter<int>::from_capacity(0, 0.01), std::domain_error);
  EXPECT_THROW(Compact_Quotient_Filter<int>::from_capacity(100, 0.0), std::domain_error);
  EXPECT_THROW(Compact_Quotient_Filter<int>::from_capacity(100, 1.0), std::domain_error);
}
 
TEST(CompactQuotientFilterCtor, memory_usage_is_compact)
{
  Compact_Quotient_Filter<int> qf(10, 8);       // 1024 slots, 11 bits/slot
  size_t expected_bytes = (1024 * 11 + 7) / 8;  // 1408 bytes
  EXPECT_EQ(qf.memory_usage(), expected_bytes);
 
  // Compare to standard: would be 1024 * 8 = 8192 bytes
  // Savings: ~82%
  EXPECT_LT(qf.memory_usage(), 1024u * 2);
}
 
// =====================================================================
// Basic insert / contains
// =====================================================================
 
TEST(CompactQuotientFilterBasic, insert_and_contains_no_false_negatives)
{
  Compact_Quotient_Filter<int> qf(10, 8);
 
  for (int i = 0; i < 100; ++i)
    qf.insert(i);
 
  EXPECT_EQ(qf.size(), 100u);
 
  for (int i = 0; i < 100; ++i)
    EXPECT_TRUE(qf.contains(i)) << "False negative for i=" << i;
}
 
TEST(CompactQuotientFilterBasic, absent_elements_usually_not_found)
{
  Compact_Quotient_Filter<int> qf(12, 10);
 
  for (int i = 0; i < 100; ++i)
    qf.insert(i);
 
  size_t false_positives = 0;
  for (int i = 1000; i < 2000; ++i)
    if (qf.contains(i))
      ++false_positives;
 
  // With r=10, FP rate ≈ 1/1024 ≈ 0.1%.
  // Testing 1000 elements: expect < 10 false positives.
  EXPECT_LT(false_positives, 20u) << "Too many false positives: " << false_positives;
}
 
TEST(CompactQuotientFilterBasic, duplicate_insert_is_idempotent)
{
  Compact_Quotient_Filter<int> qf(8, 8);
 
  qf.insert(42);
  EXPECT_EQ(qf.size(), 1u);
 
  qf.insert(42);
  EXPECT_EQ(qf.size(), 1u);
 
  EXPECT_TRUE(qf.contains(42));
}
 
TEST(CompactQuotientFilterBasic, string_keys)
{
  Compact_Quotient_Filter<string> qf(10, 8);
 
  qf.insert("hello");
  qf.insert("world");
  qf.insert("aleph");
 
  EXPECT_TRUE(qf.contains("hello"));
  EXPECT_TRUE(qf.contains("world"));
  EXPECT_TRUE(qf.contains("aleph"));
 
  EXPECT_EQ(qf.size(), 3u);
}
 
TEST(CompactQuotientFilterBasic, small_remainder_bits)
{
  // Test with very small r (high FP rate but minimal memory)
  Compact_Quotient_Filter<int> qf(8, 4);  // 256 slots, 7 bits/slot
 
  for (int i = 0; i < 50; ++i)
    qf.insert(i);
 
  for (int i = 0; i < 50; ++i)
    EXPECT_TRUE(qf.contains(i));
 
  // Memory should be tiny: 256 * 7 / 8 = 224 bytes
  EXPECT_EQ(qf.memory_usage(), 224u);
}
 
TEST(CompactQuotientFilterBasic, large_remainder_bits)
{
  // Test with large r (low FP rate)
  Compact_Quotient_Filter<int> qf(8, 20);  // 256 slots, 23 bits/slot
 
  for (int i = 0; i < 50; ++i)
    qf.insert(i);
 
  for (int i = 0; i < 50; ++i)
    EXPECT_TRUE(qf.contains(i));
 
  // FP rate should be ~2^-20 ≈ 0.0001%
  EXPECT_LT(qf.false_positive_rate(), 0.000002);
}
 
// =====================================================================
// Deletion
// =====================================================================
 
TEST(CompactQuotientFilterDelete, remove_existing_element)
{
  Compact_Quotient_Filter<int> qf(8, 8);
 
  qf.insert(10);
  qf.insert(20);
  qf.insert(30);
  EXPECT_EQ(qf.size(), 3u);
 
  EXPECT_TRUE(qf.remove(20));
  EXPECT_EQ(qf.size(), 2u);
  EXPECT_FALSE(qf.contains(20));
  EXPECT_TRUE(qf.contains(10));
  EXPECT_TRUE(qf.contains(30));
}
 
TEST(CompactQuotientFilterDelete, remove_nonexistent_is_noop)
{
  Compact_Quotient_Filter<int> qf(8, 8);
 
  qf.insert(1);
  EXPECT_FALSE(qf.remove(999));
  EXPECT_EQ(qf.size(), 1u);
  EXPECT_TRUE(qf.contains(1));
}
 
TEST(CompactQuotientFilterDelete, remove_all_makes_empty)
{
  Compact_Quotient_Filter<int> qf(8, 8);
 
  for (int i = 0; i < 50; ++i)
    qf.insert(i);
 
  for (int i = 0; i < 50; ++i)
    EXPECT_TRUE(qf.remove(i)) << "Failed to remove i=" << i;
 
  EXPECT_EQ(qf.size(), 0u);
  EXPECT_TRUE(qf.is_empty());
}
 
TEST(CompactQuotientFilterDelete, insert_after_remove)
{
  Compact_Quotient_Filter<int> qf(8, 8);
 
  qf.insert(5);
  qf.remove(5);
  EXPECT_FALSE(qf.contains(5));
 
  qf.insert(5);
  EXPECT_TRUE(qf.contains(5));
  EXPECT_EQ(qf.size(), 1u);
}
 
TEST(CompactQuotientFilterDelete, interleaved_insert_remove)
{
  Compact_Quotient_Filter<int> qf(10, 8);
 
  for (int i = 0; i < 100; ++i)
    qf.insert(i);
 
  // Remove every other element
  for (int i = 0; i < 100; i += 2)
    EXPECT_TRUE(qf.remove(i));
 
  EXPECT_EQ(qf.size(), 50u);
 
  // Verify odd elements remain
  for (int i = 1; i < 100; i += 2)
    EXPECT_TRUE(qf.contains(i)) << "Lost i=" << i;
 
  // Verify even elements removed
  for (int i = 0; i < 100; i += 2)
    EXPECT_FALSE(qf.contains(i)) << "Still has i=" << i;
}
 
// =====================================================================
// Capacity and overflow
// =====================================================================
 
TEST(CompactQuotientFilterCapacity, load_factor_computed_correctly)
{
  Compact_Quotient_Filter<int> qf(4, 8);  // 16 slots
  EXPECT_DOUBLE_EQ(qf.load_factor(), 0.0);
 
  for (int i = 0; i < 8; ++i)
    qf.insert(i);
 
  EXPECT_DOUBLE_EQ(qf.load_factor(), 0.5);
}
 
TEST(CompactQuotientFilterCapacity, overflow_throws)
{
  Compact_Quotient_Filter<int> qf(2, 8);  // 4 slots
 
  for (int i = 0; i < 4; ++i)
    qf.insert(i * 100);
 
  bool threw = false;
  for (int i = 100; i < 200; ++i)
    {
      try
        {
          qf.insert(i);
        }
      catch (const std::overflow_error &)
        {
          threw = true;
          break;
        }
    }
  EXPECT_TRUE(threw);
}
 
TEST(CompactQuotientFilterCapacity, high_load_factor_still_works)
{
  Compact_Quotient_Filter<int> qf(8, 8);  // 256 slots
 
  // Fill to 90% capacity
  for (int i = 0; i < 230; ++i)
    qf.insert(i);
 
  EXPECT_GT(qf.load_factor(), 0.85);
 
  // All elements should still be found
  for (int i = 0; i < 230; ++i)
    EXPECT_TRUE(qf.contains(i)) << "Lost i=" << i;
}
 
// =====================================================================
// Introspection
// =====================================================================
 
TEST(CompactQuotientFilterIntrospection, memory_usage)
{
  Compact_Quotient_Filter<int> qf(10, 8);
  size_t expected = (1024 * 11 + 7) / 8;  // 1024 slots * 11 bits/slot
  EXPECT_EQ(qf.memory_usage(), expected);
}
 
TEST(CompactQuotientFilterIntrospection, false_positive_rate)
{
  Compact_Quotient_Filter<int> qf(10, 8);
  double expected = 1.0 / 256.0;  // 2^{-8}
  EXPECT_DOUBLE_EQ(qf.false_positive_rate(), expected);
}
 
TEST(CompactQuotientFilterIntrospection, estimate_returns_valid_params)
{
  auto [q_val, r_val] = Compact_Quotient_Filter<int>::estimate(10000, 0.001);
  EXPECT_GE(q_val, 1);
  EXPECT_GE(r_val, 10);  // -log2(0.001) ≈ 10
  EXPECT_LE(q_val + r_val, 64);
}
 
// =====================================================================
// Copy / Move semantics
// =====================================================================
 
TEST(CompactQuotientFilterSemantics, copy_preserves_state)
{
  Compact_Quotient_Filter<int> qf(8, 8);
  for (int i = 0; i < 30; ++i)
    qf.insert(i);
 
  Compact_Quotient_Filter<int> copy(qf);
  EXPECT_EQ(copy.size(), qf.size());
  EXPECT_EQ(copy.q(), qf.q());
  EXPECT_EQ(copy.r(), qf.r());
 
  for (int i = 0; i < 30; ++i)
    EXPECT_TRUE(copy.contains(i));
}
 
TEST(CompactQuotientFilterSemantics, move_transfers_state)
{
  Compact_Quotient_Filter<int> qf(8, 8);
  for (int i = 0; i < 30; ++i)
    qf.insert(i);
 
  size_t orig_size = qf.size();
  Compact_Quotient_Filter<int> moved(std::move(qf));
 
  EXPECT_EQ(moved.size(), orig_size);
  for (int i = 0; i < 30; ++i)
    EXPECT_TRUE(moved.contains(i));
}
 
TEST(CompactQuotientFilterSemantics, swap_works)
{
  Compact_Quotient_Filter<int> a(8, 8);
  Compact_Quotient_Filter<int> b(8, 8);
 
  a.insert(1);
  b.insert(2);
 
  a.swap(b);
  EXPECT_TRUE(a.contains(2));
  EXPECT_TRUE(b.contains(1));
}
 
// =====================================================================
// Clear
// =====================================================================
 
TEST(CompactQuotientFilterClear, clears_all_state)
{
  Compact_Quotient_Filter<int> qf(8, 8);
  for (int i = 0; i < 50; ++i)
    qf.insert(i);
 
  qf.clear();
  EXPECT_EQ(qf.size(), 0u);
  EXPECT_TRUE(qf.is_empty());
 
  for (int i = 0; i < 50; ++i)
    EXPECT_FALSE(qf.contains(i));
}
 
TEST(CompactQuotientFilterClear, can_reuse_after_clear)
{
  Compact_Quotient_Filter<int> qf(8, 8);
 
  for (int i = 0; i < 20; ++i)
    qf.insert(i);
 
  qf.clear();
 
  for (int i = 100; i < 120; ++i)
    qf.insert(i);
 
  EXPECT_EQ(qf.size(), 20u);
  for (int i = 100; i < 120; ++i)
    EXPECT_TRUE(qf.contains(i));
}
 
// =====================================================================
// Merge
// =====================================================================
 
TEST(CompactQuotientFilterMerge, merge_combines_elements)
{
  Compact_Quotient_Filter<int> a(10, 8, 42);
  Compact_Quotient_Filter<int> b(10, 8, 42);
 
  for (int i = 0; i < 50; ++i)
    a.insert(i);
  for (int i = 50; i < 100; ++i)
    b.insert(i);
 
  a.merge(b);
 
  for (int i = 0; i < 100; ++i)
    EXPECT_TRUE(a.contains(i)) << "Missing i=" << i;
}
 
TEST(CompactQuotientFilterMerge, merge_rejects_mismatched_params)
{
  Compact_Quotient_Filter<int> a(10, 8, 42);
  Compact_Quotient_Filter<int> b(10, 9, 42);  // different r
 
  EXPECT_THROW(a.merge(b), std::domain_error);
}
 
TEST(CompactQuotientFilterMerge, merge_rejects_mismatched_seed)
{
  Compact_Quotient_Filter<int> a(10, 8, 42);
  Compact_Quotient_Filter<int> b(10, 8, 99);  // different seed
 
  EXPECT_THROW(a.merge(b), std::domain_error);
}
 
TEST(CompactQuotientFilterMerge, merge_with_overlapping_elements)
{
  Compact_Quotient_Filter<int> a(10, 8, 42);
  Compact_Quotient_Filter<int> b(10, 8, 42);
 
  for (int i = 0; i < 60; ++i)
    a.insert(i);
  for (int i = 40; i < 100; ++i)
    b.insert(i);
 
  a.merge(b);
 
  // Should have union: [0, 100)
  for (int i = 0; i < 100; ++i)
    EXPECT_TRUE(a.contains(i)) << "Missing i=" << i;
}
 
// =====================================================================
// False positive rate (statistical)
// =====================================================================
 
TEST(CompactQuotientFilterFPRate, empirical_fp_rate_within_bounds)
{
  const size_t n = 500;
  Compact_Quotient_Filter<int> qf(12, 8);  // 4096 slots, FP ≈ 1/256
 
  for (size_t i = 0; i < n; ++i)
    qf.insert(static_cast<int>(i));
 
  size_t test_count = 10000;
  size_t fps = 0;
  for (size_t i = n + 10000; i < n + 10000 + test_count; ++i)
    if (qf.contains(static_cast<int>(i)))
      ++fps;
 
  double empirical = static_cast<double>(fps) / test_count;
  double theoretical = qf.false_positive_rate();
 
  // Allow 5x margin over theoretical for statistical variance.
  EXPECT_LT(empirical, theoretical * 5.0 + 0.01)
    << "Empirical FP rate " << empirical << " exceeds 5x theoretical " << theoretical;
}
 
TEST(CompactQuotientFilterFPRate, low_fp_rate_with_large_r)
{
  Compact_Quotient_Filter<int> qf(10, 16);  // r=16 → FP ≈ 1/65536
 
  for (int i = 0; i < 200; ++i)
    qf.insert(i);
 
  size_t fps = 0;
  for (int i = 10000; i < 20000; ++i)
    if (qf.contains(i))
      ++fps;
 
  // With 10000 tests and FP rate ~0.0015%, expect < 5 false positives
  EXPECT_LT(fps, 10u);
}
 
// =====================================================================
// Stress tests
// =====================================================================
 
TEST(CompactQuotientFilterStress, random_insertions_and_lookups)
{
  Compact_Quotient_Filter<int> qf(14, 10);  // 16K slots
  std::mt19937 rng(42);
  std::uniform_int_distribution<int> dist(0, 1000000);
 
  std::set<int> inserted;
 
  // Insert 5000 random elements
  for (int i = 0; i < 5000; ++i)
    {
      int val = dist(rng);
      qf.insert(val);
      inserted.insert(val);
    }
 
  // All inserted elements must be found
  for (int val : inserted)
    EXPECT_TRUE(qf.contains(val)) << "Lost value " << val;
}
 
TEST(CompactQuotientFilterStress, sequential_insert_remove_cycles)
{
  Compact_Quotient_Filter<int> qf(10, 8);  // 1024 slots
 
  for (int cycle = 0; cycle < 5; ++cycle)
    {
      qf.clear();  // Start fresh each cycle
 
      // Insert 200 elements
      for (int i = 0; i < 200; ++i)
        qf.insert(cycle * 1000 + i);
 
      // Remove half
      for (int i = 0; i < 100; ++i)
        qf.remove(cycle * 1000 + i);
 
      // Verify remaining half
      for (int i = 100; i < 200; ++i)
        EXPECT_TRUE(qf.contains(cycle * 1000 + i)) << "Cycle " << cycle << ", lost i=" << i;
    }
}
 
TEST(CompactQuotientFilterStress, collision_heavy_workload)
{
  // Small q forces many collisions
  Compact_Quotient_Filter<int> qf(6, 12);  // 64 slots, 15 bits/slot
 
  for (int i = 0; i < 40; ++i)
    qf.insert(i);
 
  for (int i = 0; i < 40; ++i)
    EXPECT_TRUE(qf.contains(i)) << "Lost i=" << i;
 
  // Remove some
  for (int i = 0; i < 20; ++i)
    EXPECT_TRUE(qf.remove(i));
 
  // Verify remaining
  for (int i = 20; i < 40; ++i)
    EXPECT_TRUE(qf.contains(i));
}
 
// =====================================================================
// Edge cases
// =====================================================================
 
TEST(CompactQuotientFilterEdge, single_slot_filter)
{
  Compact_Quotient_Filter<int> qf(1, 8);  // 2 slots
 
  qf.insert(1);
  EXPECT_TRUE(qf.contains(1));
 
  qf.insert(2);
  EXPECT_TRUE(qf.contains(1));
  EXPECT_TRUE(qf.contains(2));
}
 
TEST(CompactQuotientFilterEdge, minimal_remainder_bits)
{
  Compact_Quotient_Filter<int> qf(8, 1);  // r=1 → 50% FP rate
 
  for (int i = 0; i < 50; ++i)
    qf.insert(i);
 
  for (int i = 0; i < 50; ++i)
    EXPECT_TRUE(qf.contains(i));
}
 
TEST(CompactQuotientFilterEdge, maximal_remainder_bits)
{
  Compact_Quotient_Filter<int> qf(4, 60);  // r=60 → extremely low FP
 
  qf.insert(42);
  EXPECT_TRUE(qf.contains(42));
  EXPECT_FALSE(qf.contains(43));
}
 
TEST(CompactQuotientFilterEdge, wrap_around_behavior)
{
  Compact_Quotient_Filter<int> qf(4, 8);  // 16 slots
 
  // Force wrap-around by filling near the end
  for (int i = 0; i < 16; ++i)
    qf.insert(i);
 
  for (int i = 0; i < 16; ++i)
    EXPECT_TRUE(qf.contains(i)) << "Lost i=" << i;
}
 
// =====================================================================
// Comparison with standard Quotient_Filter
// =====================================================================
 
TEST(CompactQuotientFilterComparison, same_behavior_as_standard)
{
  const uint32_t seed = 12345;
  Quotient_Filter<int> standard(10, 8, seed);
  Compact_Quotient_Filter<int> compact(10, 8, seed);
 
  std::vector<int> values = {1, 5, 10, 42, 99, 123, 456, 789};
 
  for (int val : values)
    {
      standard.insert(val);
      compact.insert(val);
    }
 
  // Both should find all inserted elements
  for (int val : values)
    {
      EXPECT_TRUE(standard.contains(val));
      EXPECT_TRUE(compact.contains(val));
    }
 
  // Both should have same size
  EXPECT_EQ(standard.size(), compact.size());
}
 
TEST(CompactQuotientFilterComparison, memory_savings_verified)
{
  Quotient_Filter<int> standard(10, 8);
  Compact_Quotient_Filter<int> compact(10, 8);
 
  size_t standard_mem = standard.memory_usage();
  size_t compact_mem = compact.memory_usage();
 
  // Compact should use ~82% less memory
  EXPECT_LT(compact_mem, standard_mem / 5);  // < 20% of standard
 
  // Standard: 1024 slots * 8 bytes = 8192 bytes
  EXPECT_EQ(standard_mem, 8192u);
 
  // Compact: 1024 slots * 11 bits = 11264 bits = 1408 bytes
  EXPECT_EQ(compact_mem, 1408u);
}