SolverForge

Used in Production

"Working like a charm, A+" — Dr. Fawaz Halwani, Pathologist, The Ottawa Hospital

A Rust planning engine for problems where you need to assign scarce resources without breaking hard rules.

Use SolverForge when the answer depends on many coupled decisions: who works which shift, which vehicle visits which stop, which task runs on which machine, or which resource should be reserved for which job. You describe the facts, the planning variables, and the constraints. SolverForge searches for a feasible, high-scoring solution while preserving concrete Rust types through the runtime.

Most new projects should start with solverforge-cli. This repository contains the runtime crates, examples, and API references that the generated application uses after the scaffold exists.

Get Started

cargo install solverforge-cli
solverforge new my-scheduler
cd my-scheduler
solverforge generate fact resource --field category:String --field load:i32
solverforge generate entity task --field label:String --field priority:i32
solverforge generate variable resource_idx --entity Task --kind scalar --range resources --allows-unassigned
solverforge server

Open http://localhost:7860 to see your solver in action.

That sequence creates a complete local SolverForge application, adds a resource fact, adds a task planning entity, gives each task an optional scalar assignment, and starts the generated web server.

The CLI is intentionally neutral. solverforge new <name> gives you the shell; solverforge generate ... adds facts, entities, variables, constraints, and demo data as your domain becomes clearer. Generated applications can mix scalar planning variables with independent planning lists, and they use the same solverforge facade crate documented here.

Extend the Scaffold

• Extend the domain when you need more entities, facts, variables, scoring, or mixed scalar/list modeling inside a generated app.
• Extend the solver when you need custom phases, selectors, termination, or solver configuration beyond the scaffold defaults.

Documentation Map

• New users should start with this README and the complete packages under examples/.
• Generated app work starts in the standalone solverforge-cli repository, then continues against the runtime crates in this workspace.
• docs/extend-domain.md and docs/extend-solver.md cover scaffold extension workflows.
• docs/lifecycle-pause-resume-contract.md defines the retained lifecycle contract, including exact pause/resume semantics, snapshot identity, and terminal-state cleanup rules.
• docs/naming-charter.md is the canonical naming contract for scalar/list terminology and selector-family cleanup.
• docs/naming-contract-audit.md records the current neutral selector and extractor naming model.
• crates/*/WIREFRAME.md files are the canonical public API maps for each crate.
• AGENTS.md defines repository-level engineering and documentation expectations for coding agents.

Zero-Erasure Architecture

SolverForge preserves concrete types through the entire solver pipeline:

• No trait objects (Box<dyn Trait>, Arc<dyn Trait>)
• No runtime dispatch - all generics resolved at compile time
• No hidden allocations - moves, scores, and constraints are stack-allocated
• Deterministic neighborhood order - canonical list, nearby-list, and sublist selector enumeration keeps seeded local search reproducible
• Predictable performance - no GC pauses, no vtable lookups

This enables aggressive compiler optimizations and cache-friendly data layouts.

Current public naming follows neutral Rust contracts rather than helper-role prefixes. The object-safe descriptor boundary is still intentional, but the concrete adapter and selector surface are now documented as EntityCollectionExtractor, ValueSelector, and MoveSelector. The historical rename and rationale are captured in docs/naming-contract-audit.md.

Features

• Score Types: SoftScore, HardSoftScore, HardMediumSoftScore, BendableScore, HardSoftDecimalScore
• ConstraintStream API: Declarative constraints with fluent builders, model-owned collection sources, single-source and cross-join projected scoring rows, existence checks, joins, grouping, consecutive_runs, and balance/complemented streams
• SERIO Engine: Scoring Engine for Real-time Incremental Optimization
• Solver Phases:
  • Generic Construction Heuristics (FirstFit, CheapestInsertion) over one mixed scalar/list runtime plan when matching list work is present, plus descriptor construction routing for scalar-only targets and specialized list phases (ListRoundRobin, ListCheapestInsertion, ListRegretInsertion, ListClarkeWright, ListKOpt)
  • Grouped scalar construction for named ScalarGroup declarations, including candidate-backed compound edits and assignment-backed nullable scalar construction with required-slot handling, capacity repair, and heuristic ordering hooks
  • Local Search (Hill Climbing, Simulated Annealing, Tabu Search, Late Acceptance, Great Deluge, Step Counting Hill Climbing, Diversified Late Acceptance)
  • Exhaustive Search (Branch and Bound with DFS/BFS/Score-First)
  • Partitioned Search (multi-threaded via rayon)
  • VND (Variable Neighborhood Descent)
• Move System: Zero-allocation moves with cursor-scoped ownership and selected-winner materialization
  • Scalar: ChangeMove, SwapMove, PillarChangeMove, PillarSwapMove, RuinMove
  • List: ListChangeMove, ListSwapMove, SublistChangeMove, SublistSwapMove, KOptMove, ListRuinMove
  • Scalar ruin-recreate, composite moves, cartesian composition, and nearby selection for scalar and list neighborhoods
• SolverManager API: Retained job / snapshot / checkpoint lifecycle with exact pause/resume, lifecycle-complete events, snapshot retrieval, snapshot-bound analysis, and telemetry
• Model Macros: planning_model!, #[planning_solution], #[planning_entity], #[problem_fact]
• Configuration: TOML/YAML support with builder API, bounded scalar candidate limits, grouped scalar move selectors, conflict-repair selectors, selector telemetry, and level-aware simulated annealing configuration
• Console Output: Colorful tracing-based progress display with solve telemetry

Grouped scoring weights receive both the group key and collected result:

ConstraintFactory::<Schedule, HardSoftScore>::new()
    .for_each(Schedule::shifts())
    .filter(|shift: &Shift| shift.nurse_idx.is_some())
    .group_by(
        |shift: &Shift| shift.nurse_idx.unwrap_or(usize::MAX),
        consecutive_runs(|shift: &Shift| shift.day),
    )
    .penalize_with(|_nurse_idx: &usize, runs: &Runs| {
        let excess_days = runs
            .runs()
            .iter()
            .map(|run| run.point_count().saturating_sub(2) as i64)
            .sum();
        HardSoftScore::of_soft(excess_days)
    })
    .named("Long work streaks");

Installation

If you are building directly against the runtime crates instead of starting from solverforge-cli, add the facade crate to your Cargo.toml:

[dependencies]
solverforge = { version = "0.12.1", features = ["console"] }

When move_selector is omitted from local search or VND, the canonical runtime uses explicit streaming defaults instead of broad exhaustive neighborhoods:

• scalar-only models default to ChangeMoveSelector plus SwapMoveSelector
• list-only models default to NearbyListChangeMoveSelector(20), NearbyListSwapMoveSelector(20), and ListReverseMoveSelector
• mixed models concatenate the list defaults first, then the scalar defaults

Runtime telemetry now preserves exact counts and Durations through the whole pipeline. Retained status/events expose generated, evaluated, and accepted move counts together with generation and evaluation durations; human-facing moves/s remains a display-only derived value.

Neighborhood selector cleanup is benchmark-gated in the runtime crates. Shared support code backs exact sizing and reusable bookkeeping, while the move-enumeration hot loops for list and sublist neighborhoods stay explicit and monomorphized.

Feature Flags

Feature	Description
console	Colorful console output with progress tracking
verbose-logging	DEBUG-level progress updates (1/sec during local search)
decimal	Decimal score support via rust_decimal
serde	Serialization support for domain types

Quick Start

The README quickstart is the checked-in minimal-shift-scheduling package. It is small enough to read in one sitting, but it is still a real SolverForge model: make examples builds it, and the command below compiles and runs it from the workspace.

cargo run -p minimal-shift-scheduling

A successful run prints a feasible nurse assignment:

score: 0hard/0soft
day 0 slot 0 -> Amina
day 0 slot 1 -> Bruno
day 1 slot 0 -> Bruno
day 1 slot 1 -> Chiara
day 2 slot 0 -> Chiara
day 2 slot 1 -> Amina
day 3 slot 0 -> Amina
day 3 slot 1 -> Bruno
day 4 slot 0 -> Bruno
day 4 slot 1 -> Chiara
day 5 slot 0 -> Chiara
day 5 slot 1 -> Amina

Read the quickstart files in this order:

• src/domain/mod.rs declares the model with solverforge::planning_model!.
• src/domain/nurse.rs defines the problem facts.
• src/domain/shift.rs defines the planning entities and the nurse_idx planning variable.
• src/domain/schedule.rs owns the solution, constraints, solver.toml link, and assignment-backed ScalarGroup hooks.
• solver.toml configures required-shift assignment construction and grouped scalar local search.
• src/main.rs builds a small schedule, starts SolverManager, consumes solver events, and prints the completed assignment.

The important boundary is that SolverForge model metadata is owned by the model, not by detached helper imports. The domain manifest lists normal Rust modules; the #[planning_solution] macro generates collection source functions such as Schedule::shifts(), and constraints use those functions through ConstraintFactory::for_each(...).

For a new application, start with solverforge-cli so the file layout, solver.toml, model manifest, constraints, and frontend handoff are generated together. Use the runtime crates directly when you want to embed SolverForge in an existing Rust service or build lower-level integrations.

Console Output

With features = ["console"], SolverForge displays colorful progress:

The solve-start line is shape-aware: list models show elements, and scalar models show average candidates.

 ____        _                 _____
/ ___|  ___ | |_   _____ _ __ |  ___|__  _ __ __ _  ___
\___ \ / _ \| \ \ / / _ \ '__|| |_ / _ \| '__/ _` |/ _ \
 ___) | (_) | |\ V /  __/ |   |  _| (_) | | | (_| |  __/
|____/ \___/|_| \_/ \___|_|   |_|  \___/|_|  \__, |\___|
                                             |___/
                   v0.12.1 - Zero-Erasure Constraint Solver

  0.000s ▶ Solving │ 14 entities │ 5 candidates │ scale 9.799 x 10^0
  0.001s ▶ Construction Heuristic started
  0.002s ◀ Construction Heuristic ended │ 1ms │ 14 steps │ 14,000/s │ 0hard/-50soft
  0.002s ▶ Local Search started │ 0hard/-50soft
  1.002s ⚡    12,456 steps │      445,000/s │ -2hard/8soft
  2.003s ⚡    24,891 steps │      448,000/s │ 0hard/12soft
 30.001s ◀ Local Search ended │ 30.00s │ 104,864 steps │ 456,000/s │ 0hard/15soft
 30.001s ■ Solving complete │ 0hard/15soft │ FEASIBLE

╔══════════════════════════════════════════════════════════╗
║                 FEASIBLE SOLUTION FOUND                  ║
╠══════════════════════════════════════════════════════════╣
║  Final Score:                            0hard/15soft    ║
║  Moves Generated:                            104,864     ║
║  Steps:                                      104,864     ║
║  Generation Time:                              1.24s     ║
║  Evaluation Time:                             28.76s     ║
║  Moves/s:                                    456,000     ║
║  Moves Evaluated:                            104,864     ║
║  Moves Accepted:                              12,456     ║
║  Score Calcs:                                104,864     ║
║  Acceptance:                                  11.9%      ║
╚══════════════════════════════════════════════════════════╝

Log Levels

Level	Content	When
INFO	Lifecycle events (solve/phase start/end)	Default
DEBUG	Progress updates (1/sec with speed and score)	verbose-logging feature
TRACE	Individual move evaluations	RUST_LOG=solverforge_solver=trace

Architecture

┌─────────────────────────────────────────────────────────────────┐
│                         solverforge                             │
│                    (facade + re-exports)                        │
└─────────────────────────────────────────────────────────────────┘
        │              │              │              │
        ▼              ▼              ▼              ▼
┌──────────────┬──────────────┬──────────────┬──────────────┐
│solverforge-  │solverforge-  │solverforge-  │solverforge-  │
│   solver     │   scoring    │   config     │   console    │
│              │              │              │              │
│ • Phases     │ • Constraint │ • TOML       │ • Banner     │
│ • Moves      │   Streams    │ • Builders   │ • Tracing    │
│ • Selectors  │ • Score      │              │ • Progress   │
│ • Acceptors  │   Directors  │              │              │
│ • Termination│ • SERIO      │              │              │
│ • Manager    │   Engine     │              │              │
│ • Telemetry  │              │              │              │
└──────────────┴──────────────┴──────────────┴──────────────┘
        │              │
        └──────┬───────┘
               ▼
        ┌──────────────────────────────┐
        │       solverforge-core       │
        │                              │
        │ • Score types                │
        │ • Domain traits              │
        │ • Descriptors                │
        │ • Variable system            │
        └──────────────────────────────┘
                       │
                       ▼
        ┌──────────────────────────────┐
        │      solverforge-macros      │
        │                              │
        │ • planning_model!           │
        │ • #[planning_solution]       │
        │ • #[planning_entity]         │
        │ • #[problem_fact]            │
        └──────────────────────────────┘

Crate Overview

Crate	Purpose
solverforge	Main facade with prelude and re-exports
solverforge-core	Core types: scores, domain traits, descriptors
solverforge-solver	Solver engine: phases, moves, termination, SolverManager, telemetry
solverforge-scoring	ConstraintStream API, SERIO incremental scoring
solverforge-config	Configuration via TOML and builder API
solverforge-console	Tracing-based console output with banner and progress display
solverforge-macros	Procedural macros for domain model
solverforge-cvrp	CVRP domain helpers: VrpSolution, ProblemData, distance meters, feasibility functions
solverforge-test	Shared test fixtures for workspace crates

Score Types

use solverforge::prelude::*;

// Single-level score
let score = SoftScore::of(-5);

// Two-level score (hard + soft)
let score = HardSoftScore::of(-2, 100);
assert!(!score.is_feasible());  // Hard score < 0

// Three-level score
let score = HardMediumSoftScore::of(0, -50, 200);

// Decimal precision
let score = HardSoftDecimalScore::of_scaled(0, -12_345_000);

// N-level configurable
let score = BendableScore::<2, 2>::of([0, -1], [-50, -100]);

Termination

Configure via solver.toml:

[termination]
seconds_spent_limit = 30
unimproved_seconds_spent_limit = 5
step_count_limit = 10000

Or programmatically:

let config = SolverConfig::load("solver.toml").unwrap_or_default();

For macro-generated retained solves, the solution module listed by planning_model! can use config = "..." to decorate the loaded solver.toml config instead of replacing it:

#[planning_solution(
    constraints = "define_constraints",
    config = "solver_config_for_solution"
)]
pub struct Schedule {
    // ...
}

fn solver_config_for_solution(solution: &Schedule, config: SolverConfig) -> SolverConfig {
    config.with_termination_seconds(solution.time_limit_secs)
}

SolverManager API

The SolverManager owns the retained runtime lifecycle for each job. The public contract uses neutral job, snapshot, and checkpoint terminology throughout the API. pause() settles at a runtime-owned safe boundary and resume() continues from the exact in-process checkpoint rather than restarting from the best solution. Built-in search phases now poll retained-runtime control during large neighborhood generation and evaluation, so config time limits, pause(), and cancel() unwind promptly without app-side watchdogs. Declare a static instance so it satisfies the 'static lifetime requirement:

use solverforge::{SolverLifecycleState, SolverManager, SolverStatus, Solvable};

static MANAGER: SolverManager<MySchedule> = SolverManager::new();

let (job_id, mut events) = MANAGER.solve(problem).unwrap();

let status: SolverStatus<_> = MANAGER.get_status(job_id).unwrap();
assert_eq!(status.lifecycle_state, SolverLifecycleState::Solving);

MANAGER.pause(job_id).unwrap();
MANAGER.resume(job_id).unwrap();
MANAGER.cancel(job_id).unwrap();

let snapshot = MANAGER.get_snapshot(job_id, None).unwrap();
let analysis = MANAGER.analyze_snapshot(job_id, Some(snapshot.snapshot_revision)).unwrap();
MANAGER.delete(job_id).unwrap();

Lifecycle events carry job_id, monotonic event_sequence, snapshot_revision, telemetry, and authoritative lifecycle state. Progress metadata reflects the current runtime state, including PauseRequested while a pause is settling. After pause() is accepted, the stream delivers PauseRequested before any later worker-side event already published in PauseRequested state. Snapshot analysis is always bound to a retained snapshot_revision, whether the job is still solving, pause-requested, paused, or already terminal, and analysis availability must never be treated as proof that a job has completed. delete is reserved for cleanup of terminal jobs only: it removes the retained job from the public API immediately, and the underlying slot becomes reusable once the worker has fully exited.

Score Analysis

Analyze solutions without solving:

use solverforge::analyze;

let analysis = analyze(&solution);

println!("Score: {}", analysis.score);
for constraint in &analysis.constraints {
    println!("  {}: {}", constraint.name, constraint.score);
}

Examples

Root workspace examples live under examples/ as complete solver packages:

make examples
cargo run -p scalar-graph-coloring
cargo run -p minimal-shift-scheduling
cargo run -p list-tsp
cargo run -p mixed-job-shop
cargo run -p nqueens

make examples builds every checked-in example package. Run an individual cargo run -p ... command when you want to inspect one model's behavior.

minimal-shift-scheduling is the compact public solver path: it uses planning_model!, generated collection sources, solver.toml, assignment-backed ScalarGroup, consecutive_runs, and SolverManager.

For project scaffolding and end-to-end application templates, use the standalone solverforge-cli repository: cargo install solverforge-cli, then solverforge new ....

Performance

SolverForge leverages Rust's zero-cost abstractions:

• Zero-Erasure Moves: Values stored inline, no boxing, arena-based ownership (never cloned)
• RPITIT Selectors: Return-position impl Trait eliminates Box<dyn Iterator> from all selectors
• Incremental Scoring: SERIO propagates only changed constraints
• No GC: Predictable latency without garbage collection
• Cache-friendly: Contiguous memory layouts for hot paths
• No vtable dispatch: Monomorphized score directors, deciders, and bounders

Typical throughput: 300k-1M moves/second depending on constraint complexity for scheduling; 2.5M+ moves/second on VRP

Status

Current workspace version: 0.12.1

The current checked-in workspace exposes:

• the solverforge facade crate for application code;
• solverforge-cli as the recommended first project path;
• model-owned planning_model! domains with generated collection sources;
• scalar, list, grouped-scalar, assignment-backed scalar-group, conflict-repair, ruin-recreate, cartesian, and nearby neighborhoods;
• retained SolverManager jobs with progress events, exact pause/resume, snapshots, checkpoint status, telemetry, and snapshot-bound analysis;
• TOML/YAML solver configuration plus programmatic overrides;
• optional console rendering through the console feature; and
• five workspace examples validated by make examples.

Release history belongs in CHANGELOG.md. Maintainer release steps live in RELEASE.md.

Release Operations

The workspace release checklist, publish order, and crate stability matrix live in RELEASE.md. Version bumps are explicit release decisions, and CHANGELOG.md remains managed by the commit-and-tag-version workflow rather than hand-maintained in feature branches.

Minimum Rust Version

Rust 1.95 or later.

License

Apache License 2.0. See LICENSE.

Contributing

Contributions welcome. Please open an issue or pull request.