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Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[1.0.3] - 2026-01-24

Fixed

  • Variable-name objectives return zero - When optimize names a variable directly (e.g., optimize: "x") rather than a coefficient attribute, the solver now correctly assigns an implicit cost of 1 to that variable instead of producing a trivial zero objective. (#121, reported by @Daniel-Alievsky)
  • Solver hangs on degenerate LPs - Both phases of the simplex could cycle indefinitely on problems with many redundant bound constraints (e.g., 300+ variables with explicit min/max bounds). Phase 1 now detects non-convergence and falls back to Bland's rule with lazy matrix save/restore; phase 2 detects stalled objectives and terminates degenerate cycling. (#112, reported by @luke-thorburn)
  • Unrestricted variables with Big-M report false infeasibility - Phase 1 of the simplex incorrectly treated negative-valued unrestricted basic variables as infeasibility violations, causing models with unrestricted variables and Big-M constraints (e.g., absolute value formulations |x| >= C) to return feasible: false or find suboptimal solutions. Phase 1 now skips unrestricted basic variables when checking feasibility and prefers entering columns that directly fix infeasibility. (#130, reported by @robwieringa)

Performance

  • B&B node pruning - Branch-and-bound now prunes nodes whose LP relaxation bound equals the best known integer solution, avoiding unnecessary LP re-solves on provably non-improving nodes. (#90)

[1.0.1] - 2026-01-12

Performance

  • Pivot row caching - Cache normalized pivot row values for better memory locality (15-30% simplex improvement)
  • Hash-based cycle detection - Replace O(n²) algorithm with O(1) Map lookup (5-8% improvement when enabled)
  • Matrix over-allocation - Reduce reallocation frequency during cut addition
  • Pre-computed inverse quotient - Multiply instead of divide in inner loops

Changed

  • Updated README benchmarks with proper statistical methodology (10 runs, averaged)
  • Added useMIRCuts option to API documentation

Fixed

  • Fixed pseudo-cost fractionality tracking in enhanced branch-and-cut
  • Fixed lint warnings for unused variables

[1.0.0] - 2026-01-05

Breaking Changes

  • Full TypeScript rewrite - The library is now written in TypeScript with full type definitions included
  • Build system changed - Migrated from Grunt to Rollup for modern ESM/CJS dual packaging
  • Minimum Node.js version - Now requires Node.js 16+ (for ESM support)

Added

  • Full TypeScript type definitions (dist/index.d.ts)
  • ESM module support (dist/index.mjs) alongside CommonJS (dist/index.cjs)
  • Browser-specific bundle (dist/index.browser.mjs)
  • Presolve module - Automatic problem simplification before solving
  • Enhanced branch-and-cut - New solver options for MIP problems:
    • useMIRCuts - Mixed Integer Rounding cuts
    • useGomoryCuts - Gomory fractional cuts
    • presolve - Enable/disable preprocessing
    • timeout - Time limit for solving
    • tolerance - Optimality gap tolerance
  • Solver options API - Configure solver behavior via options object
  • Vitest test suite with coverage reporting
  • Security documentation (SECURITY.md)
  • Input validation with warnings for common typos

Changed

  • Internal matrix representation uses Float64Array for better performance
  • Branch-and-cut refactored into injectable service architecture
  • Improved code organization with kebab-case file naming
  • Source maps included for debugging

Performance

  • ~2-5x faster on large MIP problems due to:
    • Flat array matrix storage
    • Partial pricing in simplex
    • Presolve reductions
    • Sparse-aware pivot operations

Fixed

  • Various numerical stability improvements
  • Better handling of degenerate pivots

Removed

  • Grunt build system
  • Large static test data files (replaced with random problem generator)

[0.4.24] - Previous Release

See git history for changes prior to 1.0.0