oximo v0.7.0

oximo v0.7.0

This release adds first-class SOS1/SOS2 and indicator constraints, expands nonlinear expression support, and improves expression evaluation and large indexed model construction. It also updates POUNCE, adds shared solver lowering and reconstruction, and improves LP/MPS interoperability.

Breaking changes

• Minimum supported Rust version is now 1.89 (up from 1.85).
• Constraint declarations return model-bound handles (oximo-core)
  • Constraint and indexed constraint APIs now return handles, including range handles where a range can lower to one or two rows. Use .id() (or .ids() for range handles) when an API expects a raw ID.
• Model operations validate expression ownership (oximo-core)
  • Model::fix, set_initial, and set_param now return Result and report ModelMismatchError for expressions from another model. Handle or explicitly discard these results as appropriate.
• Expression arena access (oximo-core, oximo-expr)
  • Model::arena() now returns an ExprArenaSnapshot instead of Ref<ExprArena>. Use the snapshot's read APIs; direct mutable access is no longer available through this accessor.

Added

• SOS1 and SOS2 constraints (oximo-core, #72, #73, #74)

  • Added sos_constraint! and programmatic APIs for declaring special ordered sets.
  • Added SOS support to LP/MPS I/O and solver backends, plus SOS-to-MILP reformulation for backends without native support.
  • Added access to reformulation artifacts and SOS examples.

• Indicator constraints (oximo-core, #100, #101)

  • Added scalar, ranged, and indexed indicator declarations through indicator_constraint! and model APIs.
  • Added native backend paths where supported and a configurable reformulation path for other solvers.
  • LP/MPS readers and writers now handle indicator constraints.

• Expression evaluation and nonlinear operators (oximo-expr, oximo-autodiff, #94, #97)

  • Added stack-safe, sharing-aware expression traversal, evaluation, and extraction for deep expression DAGs.
  • Added reusable compiled expression and batch evaluators.
  • Expanded nonlinear operators supported by expression evaluation, autodiff, and model I/O.

• Shared solver lowering and reconstruction (oximo-solver, #93)

  • Added common preparation, lowering, and result reconstruction utilities for solver backends.
  • Added conformance coverage for quadratic and conic lowering across backends.

• Indexed construction and constraint handles (#85, #89)

  • Large indexed model families can be prepared in parallel while preserving registration order.
  • Indexed and ranged constraints expose handles for accessing their registered rows.

• POUNCE improvements (oximo-pounce, #88, #98, #102)

  • Updated to pounce-rs 0.12.
  • Added FBBT expression tapes and a second-opinion solve ladder for TNLP models.
  • Exposed additional POUNCE options and improved persistent model handling.

• Sparse autodiff performance (oximo-autodiff, #75, #76, #77)

  • Added packed sparsity storage, improved coloring, and reusable Hessian sparsity patterns.

Changed

• Solver backends now share more of their expression preparation, reformulation, and solution reconstruction logic. Result normalization clears stale optimality gaps when no valid incumbent remains.
• Model-bound expression and constraint handles now detect cross-model use, preventing accidental ID collisions between models.
• LP/MPS/NL writing now supports feasibility models; LP parsing handles leading negative coefficients and reports a missing objective sense as an I/O error.

Full changelog

v0.6.0...v0.7.0