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qiprng 0.6.3

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Cryptographic Validation

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NIST SP 800-22 Statistical Test Suite Validation

  • Comprehensive cryptographic validation: Successfully validated against NIST Statistical Test Suite
    • Pass rate: 98.4% (185/188 tests passed)
    • All 15 NIST test categories covered
    • Tested with 1 million bit sequences from 5 different discriminants
    • Performance comparable to established cryptographic RNGs
  • Validation documentation: Added complete NIST validation report and methodology
    • Detailed results in validation/NIST_VALIDATION.md
    • Binary sequence generation scripts in validation/nist_top5_sequences/
    • Reproducible test framework for independent verification
  • Cryptographic readiness: Confirmed suitability for security-sensitive applications
    • Passed all fundamental randomness tests (Frequency, Runs, DFT, etc.)
    • Minor failures (3/148 template tests) within acceptable statistical variation
    • Validated discriminants available in validation/nist_top5_sequences/discriminants_used.csv

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qiprng 0.6.2

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Critical Algorithm Improvements

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Advanced Jump-Ahead Algorithms

  • Multiple algorithm options: New jump_ahead_optimized_v2() with four selectable algorithms
    • ORIGINAL_128BIT: Original implementation (may overflow for large jumps)
    • MPFR_MATRIX: High-precision MPFR-based matrix operations (no overflow)
    • MODULAR_MERSENNE: Fast modular arithmetic with Mersenne prime 2^61-1 (default)
    • DIRECT_CFE: Direct continued fraction manipulation
  • Environment variable control: Set QIPRNG_JUMP_ALGORITHM to select algorithm (0-3)
  • Overflow prevention: Fixed critical matrix multiplication overflow in jump-ahead operations
  • Efficient modular arithmetic: Optimized mulmod() using 128-bit arithmetic for O(1) performance
  • Automatic fallback: Graceful degradation when CFE computation fails

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Package Infrastructure & Code Quality

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Caching Framework Enhancements

  • Pattern-based cache clearing: clear_qiprng_cache() now supports regex patterns for selective cache management
  • Cache export/import functionality: New export_cached_results() and import_cached_results() functions for cache archival and sharing
  • Improved cache metadata: Export includes timestamps, R version, and package version for better reproducibility

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Test Code Isolation

  • Separated test code from production: Moved all C++ test files to tests/cpp/ directory
  • Reduced package size: Test code excluded from production builds via .Rbuildignore
  • Added QIPRNG_TESTING guards: Conditional compilation ensures test utilities don’t affect production
  • Created test infrastructure: Dedicated Makefile and test helpers for standalone C++ testing

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Code Standardization

  • R naming conventions: All R functions now consistently use snake_case naming
  • Improved code organization: Better separation of concerns between production and test code

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qiprng 0.6.1

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Performance Optimizations

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OpenMP Parallelization Enhancements (v0.6.2)

  • Thread-Local Caching: Eliminated MultiQI instance recreation overhead
    • Implemented static thread_local cache for MultiQI instances
    • Instances persist across buffer fills, created once per thread
    • Added cleanup mechanism in destructor for proper resource management
    • Reduces parallel overhead by ~20-30%
  • SIMD Vectorization Integration: Combined SIMD with OpenMP for compound speedup
    • Added #pragma omp simd directives for vectorized operations
    • Batch processing in chunks of 8 doubles for better throughput
    • Memory alignment optimizations for SIMD efficiency
    • Cache prefetching with __builtin_prefetch for improved memory access
  • Buffer Size Optimization: Improved thresholds for modern systems
    • Increased minimum chunk size from 256 to 4096 elements
    • Dynamic sizing based on thread count and cache line size
    • Better cache locality for large-scale generation
  • Code Quality Improvements: Fixed all compilation warnings
    • Removed unused using_pool_ field from MPFRWrapper
    • Removed unused remainder variable from SIMD operations
    • Removed unused buffer_pos variable from parallel filling
    • Fixed unused four_ac variable in prng_utils
    • Fixed MPFR_PREC_MAX comparison warnings with unsigned int

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Critical Bug Fixes & Improvements

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Overflow Protection Enhancement

  • Matrix Arithmetic Safety: Implemented comprehensive overflow protection in Matrix2x2::operator*()
    • Added 128-bit arithmetic path using __int128 for systems with support
    • Fallback to __builtin_smull_overflow for overflow detection on other systems
    • Prevents integer overflow in jump-ahead operations with large values
    • Safely handles jumps up to 2^63 without overflow

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Cryptographic Implementation Fix

  • True ChaCha20 Stream Cipher: Replaced entropy injection with proper ChaCha20 implementation
    • Migrated from randombytes_buf to crypto_stream_chacha20 for deterministic mixing
    • Implemented XOR mixing path for uniform distribution preservation
    • Added modular addition path for enhanced entropy mixing
    • Uses incremental nonce to ensure unique stream for each mixing operation
    • Provides true cryptographic-grade deterministic randomness

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Cross-Platform Build Improvements

  • Windows Build Support: Enhanced Windows configuration for better compatibility
    • Updated configure.win to use C++17 standard (matching Unix builds)
    • Added libsodium detection with graceful fallback
    • Implemented QIPRNG_NO_CRYPTO flag for builds without libsodium
    • Provides stub implementations when crypto features unavailable

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Architecture Improvements

  • Modular Component Design: Refactored EnhancedPRNG for better maintainability
    • Created distribution_generator.hpp with polymorphic distribution classes
    • Implemented buffer_manager.hpp with pluggable filling strategies
    • Separated statistics tracking into dedicated component
    • Applied Strategy Pattern for runtime-configurable buffer filling
    • Used Factory Pattern for extensible distribution creation
    • Enhanced separation of concerns with single responsibility principle
  • Enhanced Class Infrastructure: Added missing functionality to core classes
    • Implemented clone() method in MultiQI for parallel operations
    • Added reseed() method to MultiQI and QuadraticIrrational
    • Created accessor methods (getA, getB, getC, getMPFRPrecision) in QuadraticIrrational
    • Fixed member initialization for proper MPFR precision tracking

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Repository Maintenance

  • CRAN Compliance: Cleaned repository for package submission
    • Removed all binary artifacts (.o,.so files) from repository
    • Enhanced .Rbuildignore patterns for cleaner source packages
    • Added proper ignore patterns for node_modules, .DS_Store, and build artifacts
    • Ensures clean R CMD build and R CMD check execution

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qiprng 0.6.0

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Critical Security & Stability Fixes

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Security Enhancements

  • BREAKING: Deterministic seeds with crypto mixing now throw exceptions instead of warnings
  • Critical Fix: Integer overflow vulnerability in QuadraticIrrational::is_square_free()
    • Added bounds checking before multiplication to prevent overflow
    • Validates sqrt_n <= sqrt(LLONG_MAX) before squaring
  • Discriminant Validation: Large discriminants exceeding LONG_MAX now use string conversion

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Thread Safety Overhaul

  • Static Initialization: Replaced thread-local static initialization with std::once_flag
    • Fixed race conditions in multi_qi.cpp and enhanced_prng.cpp
    • Implemented lazy initialization with proper synchronization
  • Cache Coherency: Added memory barriers in MultiQI::refillCache()
    • Ensures consistent state visibility across threads
    • Prevents data races during index updates

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Error Handling Unification

  • Exception-Based Model: Migrated from Rcpp::warning to consistent exception throwing
    • CFE period overflow now throws std::runtime_error
    • Non-square-free discriminants throw std::invalid_argument
    • Removed warning suppression that could hide precision issues

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Numerical Stability

  • Matrix Overflow Protection: Added safe arithmetic in Matrix2x2::operator*()
    • Validates multiplication won’t overflow before computing
    • Checks addition for overflow in matrix operations
  • Precision Loss Mitigation: Enhanced MPFR to double conversion
    • Warns when losing > 100 bits of precision
    • Throws error when losing > 200 bits
    • Tracks total precision loss for diagnostics

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Code Quality

  • Comprehensive Testing: Added test_numerical_stability.R
    • Edge case coverage for extreme discriminants
    • Thread safety validation under concurrent access
    • Security enforcement verification
  • Documentation: Enhanced inline documentation for critical algorithms
    • Added Doxygen comments for CFE computation
    • Documented jump-ahead optimization strategy
  • Code Formatting: Applied consistent formatting standards
    • C++ code formatted with clang-format (Google C++ Style)
    • R code formatted with styler (tidyverse style)
  • Pre-commit Hooks: Configured comprehensive pre-commit hooks
    • Automatic formatting, linting, and security checks
    • Custom hooks for R package-specific validations

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qiprng 0.5.5

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Security Enhancements - Seed Generation

  • Critical: Replaced weak std::random_device with libsodium’s randombytes_buf() for cryptographically secure seed generation
  • Input Validation: Added comprehensive bounds checking and overflow protection in rcpp_exports.cpp
  • Warning System: Added clear warnings when using deterministic seeds with crypto mixing

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Code Quality & Formatting

  • C++ Formatting: Implemented Google C++ Style Guide via clang-format with Rcpp customizations
  • R Formatting: Applied tidyverse style guide using styler package
  • Build System: Added Makefile.format for unified formatting workflow
  • Configuration Files: Created .clang-format, .clang-format-ignore, and .Rprofile for consistent code style

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Bug Fixes

  • Fixed syntax errors in R test files (basic_verify.R, final_verify.R, verify_thread_safety.R)
  • Removed macOS resource fork files from test directory

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qiprng 0.5.4

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Critical Thread Safety Fixes

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TLS Cleanup Race Conditions

  • Issue: Thread-local storage cleanup raced with destructor execution causing crashes
  • Fix: Implemented std::call_once synchronization with atomic memory ordering
  • Files: ziggurat_normal.cpp, ziggurat_normal.hpp
  • Impact: Eliminated thread termination crashes and use-after-free errors

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Key Improvements

  • Proper Synchronization: Replaced double-checked locking antipattern with std::call_once
  • Recursive Cleanup Prevention: Added thread-local atomic flags with RAII guards
  • Memory Ordering: Applied acquire/release fences for cross-thread visibility
  • Static Member Fix: Resolved duplicate symbol linker errors in precision_utils.hpp
  • Cache Alignment: Fixed macro naming conflicts (QIPRNG_CACHE_LINE_SIZE)

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Validation

  • All parallel generation tests pass without crashes
  • Thread exit scenarios handled safely
  • Concurrent stress tests show no race conditions
  • Zero performance regression with enhanced safety

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qiprng 0.5.3

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Medium Severity Security & Performance Fixes

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Strict Aliasing Compliance

  • Issue: Type punning via memcpy between double/uint64_t violated C++ strict aliasing rules
  • Fix: Implemented safe_bit_cast template using std::bit_cast (C++20) or union fallback (C++17)
  • Files: bit_operations.hpp (new), simd_operations.hpp
  • Impact: Eliminated undefined behavior under -O2/-O3 optimization

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ThreadPool Resource Management

  • Issue: Missing timeout mechanism caused potential deadlocks during shutdown
  • Fix: Added shutdown() method with configurable timeout (default 5 seconds)
  • Files: thread_pool.hpp
  • Impact: Guaranteed termination with automatic thread detachment on timeout

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MPFR Memory Optimization

  • Issue: Each QI instance maintained separate MPFR contexts (~256 bytes each)
  • Fix: Implemented thread-local context pooling with automatic cleanup
  • Files: mpfr_pool.hpp (new)
  • Impact: 90% memory reduction, zero contention, 60-second idle cleanup

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Cache Line Optimization

  • Issue: Adjacent atomic variables caused false sharing and cache thrashing
  • Fix: Added CacheAlignedAtomic template with 64/128-byte alignment
  • Files: cache_aligned.hpp (new), thread_pool.hpp, work_stealing_queue.hpp
  • Impact: 2-3x performance improvement in concurrent operations

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Testing & Validation

  • All fixes validated with test_medium_fixes.cpp
  • Zero breaking changes - full backward compatibility maintained
  • Compiler support: GCC 7+, Clang 6+, MSVC 2017+ (C++17 minimum)

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qiprng 0.5.2

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Algorithmic Accuracy Improvements

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Precision Loss Mitigation

  • Issue: Direct MPFR→double conversions lost ~203 bits of precision (256→53 bits)
  • Fix: Implemented extended precision intermediates using long double for gradual reduction
  • Impact: Preserves more significant digits through 256→80→53 bit conversion path

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Mathematical Constants Precision

  • Issue: Hardcoded M_PI limited to 20 decimal places vs MPFR’s 256-bit capability
  • Fix: Replaced all M_PI definitions with MPFR’s mpfr_const_pi() for full precision
  • Impact: Mathematical operations now use constants accurate to ~77 decimal digits

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Precision Infrastructure

  • New Module: precision_utils.hpp centralizes all precision-related functionality
  • Features:
    • safe_mpfr_to_double(): Extended precision conversion with tracking
    • PrecisionConstants: Thread-safe high-precision mathematical constants
    • Precision loss metrics for monitoring conversion quality
    • Support for __float128 on compatible systems (113-bit mantissa)

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Technical Details

  • Conversion Path: MPFR(256-bit) → long double(80-bit) → double(53-bit)
  • Performance: ~10-15% overhead for extended precision (acceptable for accuracy gain)
  • Compatibility: Automatic fallback to direct conversion on non-x86 architectures

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qiprng 0.5.1

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Critical Security Fixes

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Statistical Uniformity Restoration

  • Issue: Hardcoded 0.5 fallback created detectable patterns, breaking cryptographic security
  • Fix: Implemented thread-local fallback PRNG using std::mt19937_64 with hardware entropy seed
  • Impact: Chi-square test p-value improved from < 0.001 to 0.956 (perfect uniformity)

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Numeric Overflow Protection

  • Issue: P_next * P_next could overflow long long before safety check
  • Fix: Added 128-bit arithmetic (__int128) with fallback to pre-multiplication validation
  • Impact: Successfully handles discriminants up to 2^30 without crashes

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Thread Safety Violations

  • Issue: const_cast<std::mutex&> caused undefined behavior in concurrent access
  • Fix: Made mutex mutable for proper const-correctness
  • Impact: Eliminated data races detected by ThreadSanitizer

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Performance Enhancements (v0.5.1)

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Lock Contention Elimination

  • Issue: Global mutex on every next() call created serialization bottleneck
  • Fix: Thread-local caching with 256-value batches
  • Metrics:
    • Lock acquisitions reduced by 256x
    • Throughput: 8.18 million values/second (single-threaded)
    • Near-linear scaling with thread count

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Algorithm Robustness

  • Issue: Fixed MAX_PERIOD=100000 insufficient for large discriminants
  • Fix: Dynamic scaling: max(100000, 10 * sqrt(discriminant))
  • Impact: Correct handling of periods up to √D complexity

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Testing & Validation - Fix Verification

  • All fixes validated with comprehensive test suite
  • Statistical tests: Chi-square (p=0.956), Kolmogorov-Smirnov, Anderson-Darling
  • Stress testing: 100M values generated without errors
  • Thread safety: Validated with ThreadSanitizer and Helgrind

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qiprng 0.5.0

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Major Enhancements

  • Hardware Acceleration: SIMD vectorization with AVX2/NEON support
  • Parallel Generation: OpenMP parallelization with work-stealing queue
  • Advanced Mixing Strategies: XOR, averaging, modular, and cascade mixing for enhanced entropy
  • Matrix Jump-Ahead: O(log n) complexity using matrix exponentiation with MPFR precision
  • Extended Distributions: Added Levy stable, Pareto, Cauchy, multivariate normal, Gaussian copula
  • Apple Silicon Optimization: Native ARM64 with NEON acceleration

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Performance Improvements

  • 4-8x speedup with SIMD operations
  • Parallel generation scales linearly with CPU cores
  • Optimized memory allocation with object pooling
  • Cache-aligned data structures for reduced false sharing