Rust LP File Parser, Writer, and Diff Tool

Overview

A robust Rust library for parsing, modifying, and writing Linear Programming (LP) files. Built on the NOM parsing framework, 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.

Supported Specifications

• IBM CPLEX v22.1.1
• FICO Xpress
• Gurobi
• 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

• 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:

[dependencies]
lp_parser_rs = "2.4.1"

Basic Usage

Clone and run with a sample file:

git clone https://github.com/dandxy89/lp_parser_rs.git
# Parse a single LP file
cargo run --bin lp_parser --release -- {{ /path/to/your/file.lp }}
# Compare two LP files (enabling the 'diff' feature)
cargo run --bin lp_parser --release --features diff -- {{ /path/to/your/file.lp }} {{ /path/to/your/other/file.lp }}

Using the library directly:

use lp_parser::{parser::parse_file, LpProblem, writer::write_lp_string};
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

use lp_parser::{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

[dependencies]
lp_parser_rs = { version = "2.4.1", features = ["serde", "diff"] }

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

use lp_parser::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:

# 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
• LPWriter.jl
• Lp-Parser

Contributing

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