# Rust LP File Parser, Writer, and Diff Tool

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## Interactive TUI Diff Viewer (`lp_diff`)

An interactive terminal-based diff viewer for LP and MPS files, built with [ratatui](https://ratatui.rs). Compare two files (LP, MPS, or mixed) with coefficient-level detail, fuzzy search, filtering, and integrated solving via [HiGHS](https://highs.dev).

### Install

```bash
# From a cloned repo
git clone https://github.com/dandxy89/lp_parser_rs.git
cd lp_parser_rs
cargo install --path tui
```

### Quick Start

```bash
lp_diff base.lp modified.lp
```

For a non interactive summary:

```bash
lp_diff base.lp modified.lp --summary
```

### Features

- **Three-panel layout** — section selector, name list, and detail panel with coefficient-level side-by-side diffs
- **Four sections** — Summary, Variables, Constraints, and Objectives
- **Filtering** — show all (`a`), added (`+`), removed (`-`), or modified (`m`) entries
- **Telescope-style search** — fuzzy (default), regex (`r:`), or substring (`s:`) across all sections
- **HiGHS solver** — press `S` to solve either or both files and compare results
- **Vim-style navigation** — `j`/`k`, `g`/`G`, `Ctrl+d`/`Ctrl+u`, jumplist (`Ctrl+o`/`Ctrl+i`)
- **Clipboard & export** — yank names/details (`y`/`Y`), write solve diffs to CSV (`w`)
- **Built-in help** — press `?` for full keybindings reference

See [`tui/README.md`](tui/README.md) for the complete keybindings reference and detailed documentation.

## Overview

A robust Rust library for parsing, modifying, and writing Linear Programming (LP) files. Built on the [LALRPOP](https://github.com/lalrpop/lalrpop) parser generator, this crate provides comprehensive support for the LP file format with the ability to parse, programmatically modify, and regenerate LP files according to major industry specifications.

The Grammar is defined with the [lp.lalrpop](/rust/src/lp.lalrpop) file - should you be curious...

### Supported Specifications

- [IBM CPLEX v22.1.1](https://www.ibm.com/docs/en/icos/22.1.1?topic=cplex-lp-file-format-algebraic-representation)
- [FICO Xpress](https://www.fico.com/fico-xpress-optimization/docs/dms2020-03/solver/optimizer/HTML/chapter10_sec_section102.html)
- [Gurobi](https://www.gurobi.com/documentation/current/refman/lp_format.html)
- Mosek

## Features

### Core Functionality

- **Problem Definition**
  - Problem name and sense specification
  - Single and multi-objective optimisation support
  - Comprehensive constraint handling

- **Variable Support**
  - Integer, general, bounded, free, semi-continuous variables

- **LP File Writing and Modification**
  - Generate LP files from parsed problems
  - Modify objectives, constraints, and variables programmatically
  - Round-trip compatibility (parse → modify → write → parse)
  - Maintain proper LP format specifications

### Advanced Features

- **Problem Analysis**
  - Comprehensive statistics: variable/constraint counts, matrix density, sparsity metrics
  - Variable analysis: type distribution, unused/fixed variables, invalid bounds detection
  - Constraint analysis: type distribution, empty/singleton constraints, RHS ranges
  - Coefficient analysis: ranges, large/small coefficient detection, scaling ratios
  - Issue detection with severity levels (errors, warnings, info)
  - Configurable thresholds for different problem domains

- **LP File Comparison (`diff` feature)**
  - Identify added, removed, and modified elements
  - Useful for model version control and validation

- **Serialisation (`serde` feature)**
  - Full serialisation support for all model structures
  - Compatible with various data formats
  - Enables integration with other tools and systems

## Quick Start

### Installation

Add to your `Cargo.toml`:

```toml
[dependencies]
lp_parser_rs = "3.0.0" # x-release-please-version
```

### Basic Usage

Using the library directly:

```rust
use lp_parser_rs::{parser::parse_file, problem::LpProblem};
use std::path::Path;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Parse LP file content
    let content = parse_file(Path::new("problem.lp"))?;

    // Parse into LP problem structure
    let problem = LpProblem::parse(&content)?;

    // Access problem components
    println!("Problem name: {:?}", problem.name());
    println!("Objective count: {}", problem.objective_count());
    println!("Constraint count: {}", problem.constraint_count());
    println!("Variable count: {}", problem.variable_count());

    Ok(())
}
```

### LP File Writing and Modification

```rust
use lp_parser_rs::{problem::LpProblem, writer::write_lp_string, model::*};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Parse an existing LP file
    let lp_content = std::fs::read_to_string("problem.lp")?;
    let mut problem = LpProblem::parse(&lp_content)?;

    // Modify objectives
    problem.update_objective_coefficient("profit", "x1", 5.0)?;
    problem.rename_objective("profit", "total_profit")?;

    // Modify constraints
    problem.update_constraint_coefficient("capacity", "x1", 2.0)?;
    problem.update_constraint_rhs("capacity", 200.0)?;
    problem.rename_constraint("capacity", "production_limit")?;

    // Modify variables
    problem.rename_variable("x1", "production_a")?;
    problem.update_variable_type("production_a", VariableType::Integer)?;

    // Write back to LP format
    let modified_lp = write_lp_string(&problem)?;
    std::fs::write("modified_problem.lp", modified_lp)?;

    Ok(())
}
```

### Enable Optional Features

```toml
[dependencies]
lp_parser_rs = { version = "3.0.0", features = ["serde", "diff"] } # x-release-please-version
```

## Command-Line Interface

The `lp_parser` binary provides a comprehensive CLI for working with LP files.

### Installation

```bash
# Install with all features
cargo install lp_parser_rs --all-features

# Or build from source
git clone https://github.com/dandxy89/lp_parser_rs.git
cd lp_parser_rs/rust
cargo build --release --all-features
```

### Commands

```
lp_parser <COMMAND>

Commands:
  parse    Parse an LP file and display its structure
  info     Show detailed statistics about an LP problem
  analyze  Analyze problem structure, detect issues, and report statistics
  diff     Compare two LP files (requires 'diff' feature)
  convert  Convert LP file to another format
  solve    Solve an LP problem using external solvers (requires 'lp-solvers' feature)

Global Options:
  -v, --verbose    Increase output verbosity
  -q, --quiet      Suppress non-essential output
  -h, --help       Print help
  -V, --version    Print version
```

### Examples

**Parse and display an LP file:**

```bash
lp_parser parse problem.lp
```

**Get problem statistics:**

```bash
lp_parser info problem.lp
# With detailed listings
lp_parser info problem.lp --variables --constraints --objectives
```

**Analyze problem structure and detect issues:**

```bash
# Full analysis with statistics and issue detection
lp_parser analyze problem.lp

# Show only warnings and errors
lp_parser analyze problem.lp --issues-only

# Output as JSON or YAML
lp_parser analyze problem.lp --format json --pretty
lp_parser analyze problem.lp --format yaml -o analysis.yaml

# Custom thresholds for numerical issue detection
lp_parser analyze problem.lp --large-coeff-threshold 1e8 --ratio-threshold 1e5
```

Example analysis output:
```yaml
summary:
  name: diet
  sense: Minimize
  objective_count: 1
  constraint_count: 7
  variable_count: 16
  total_nonzeros: 64
  density: 0.571
sparsity:
  min_vars_per_constraint: 6
  max_vars_per_constraint: 10
variables:
  type_distribution:
    upper_bounded: 9
    double_bounded: 7
  discrete_variable_count: 0
constraints:
  type_distribution:
    equality: 7
  rhs_range:
    min: 30.0
    max: 50000.0
coefficients:
  constraint_coeff_range:
    min: 0.1
    max: 3055.2
  coefficient_ratio: 101840.0
issues: []
```

**Output as JSON or YAML:**

```bash
lp_parser info problem.lp --format json --pretty
lp_parser parse problem.lp --format yaml -o problem.yaml
```

**Compare two LP files:**

```bash
lp_parser diff old_model.lp new_model.lp
lp_parser diff old.lp new.lp --format json --pretty
```

**Convert between formats:**

```bash
# To LP (with formatting options)
lp_parser convert problem.lp --format lp --precision 4 --compact

# To CSV (creates constraints.csv, objectives.csv, variables.csv)
lp_parser convert problem.lp --format csv --output ./output_dir

# To JSON/YAML
lp_parser convert problem.lp --format json --pretty -o problem.json
lp_parser convert problem.lp --format yaml -o problem.yaml
```

**Solve with external solvers:**
```bash
# Using CBC (default)
lp_parser solve problem.lp

# Using GLPK
lp_parser solve problem.lp --solver glpk

# Output solution as JSON
lp_parser solve problem.lp --format json --pretty
```

## Solving with External Solvers (`lp-solvers` feature)

Enable the `lp-solvers` feature to solve parsed LP problems using external solvers like CBC, Gurobi, CPLEX, or GLPK via the [lp-solvers](https://crates.io/crates/lp-solvers) crate:

```toml
[dependencies]
lp_parser_rs = { version = "3.0.0", features = ["lp-solvers"] } # x-release-please-version
lp-solvers = "1.1"
```

```rust
use lp_parser_rs::{problem::LpProblem, ToLpSolvers};
use lp_solvers::solvers::{CbcSolver, SolverTrait};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let lp_content = r"
Minimize
 obj: 2 x + 3 y
Subject To
 c1: x + y <= 10
 c2: x >= 2
Bounds
 x >= 0
 y >= 0
End
";

    let problem = LpProblem::parse(lp_content)?;
    let compat = problem.to_lp_solvers()?;

    // Check for any compatibility warnings
    for warning in compat.warnings() {
        eprintln!("Warning: {}", warning);
    }

    // Solve using CBC solver (must be installed on your system)
    let solver = CbcSolver::new();
    let solution = solver.run(&compat)?;
    println!("Solution status: {:?}", solution.status);

    Ok(())
}
```

**Limitations:** The lp-solvers compatibility layer does not support multiple objectives (returns an error), strict inequalities (`<`, `>`), or SOS constraints (ignored with a warning).

## API Reference

### Problem Modification Methods

The `LpProblem` struct provides comprehensive methods for modifying LP problems:

#### Objective Modifications
- `update_objective_coefficient(objective_name, variable_name, coefficient)` - Update or add a coefficient in an objective
- `rename_objective(old_name, new_name)` - Rename an objective
- `remove_objective(objective_name)` - Remove an objective

#### Constraint Modifications
- `update_constraint_coefficient(constraint_name, variable_name, coefficient)` - Update or add a coefficient in a constraint
- `update_constraint_rhs(constraint_name, new_rhs)` - Update the right-hand side value
- `rename_constraint(old_name, new_name)` - Rename a constraint
- `remove_constraint(constraint_name)` - Remove a constraint

#### Variable Modifications
- `rename_variable(old_name, new_name)` - Rename a variable across all objectives and constraints
- `update_variable_type(variable_name, new_type)` - Change variable type (Binary, Integer, etc.)
- `remove_variable(variable_name)` - Remove a variable from all objectives and constraints

### Writing LP Files

```rust
use lp_parser_rs::writer::{write_lp_string, write_lp_string_with_options, LpWriterOptions};

// Write with default options
let lp_content = write_lp_string(&problem)?;

// Write with custom options
let options = LpWriterOptions {
    include_problem_name: true,
    max_line_length: 80,
    decimal_precision: 6,
    include_section_spacing: true,
};
let lp_content = write_lp_string_with_options(&problem, &options)?;
```

## Development

### Testing

The project uses snapshot testing via `insta` for reliable test management:

```bash
# Run all tests with all features enabled
cargo insta test --all-features

# Review snapshot changes
cargo insta review
```

## Test Data Sources

The test suite includes data from various open-source projects:

- [Jplex](https://github.com/asbestian/jplex/blob/main/instances/afiro.lp)
- [LPWriter.jl](https://github.com/odow/LPWriter.jl/blob/master/test/model2.lp)
- [Lp-Parser](https://github.com/aphi/Lp-Parser)

## Contributing

Contributions are welcome! Please feel free to submit a Pull Request.
