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https://github.com/scipopt/russcip

Rust interface for SCIP
https://github.com/scipopt/russcip

mixed-integer-programming optimization rust

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Rust interface for SCIP

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# russcip

[![tests](https://github.com/mmghannam/russcip/actions/workflows/build_and_test.yml/badge.svg)](https://github.com/mmghannam/russcip/actions/workflows/build_and_test.yml)
[![coverage](https://img.shields.io/codecov/c/github/scipopt/russcip)](https://app.codecov.io/gh/scipopt/russcip/)
[![][img_crates]][crates] [![][img_doc]][doc]

[img_crates]: https://img.shields.io/crates/v/russcip.svg

[crates]: https://crates.io/crates/russcip

[img_doc]: https://img.shields.io/badge/rust-documentation-blue.svg

[doc]: https://docs.rs/russcip/

[img_coverage]: https://img.shields.io/codecov/c/github/scipopt/russcip

A safe Rust interface for [SCIP](https://www.scipopt.org/index.php#download). This crate also exposes access to the
SCIP's C-API through the `ffi` module.
The project is currently actively developed, issues/pull-requests are very welcome.

## Installation

By running

```bash
cargo add russcip --features bundled
```

The `bundled` feature will download a precompiled SCIP as part of the build process.
This is the easiest to get started with russcip, instead you could try the [from-source](#from-source-feature)
or if you want to link against your custom SCIP installation check the [section](#custom-scip-installation) below.

### `from-source` feature

To build SCIP from source, you can enable the `from-source` feature. This will download the SCIP source code and build
it as part of the build process.

```bash
cargo add russcip --features from-source
```

This is currently the most relaiable way to get a statically-linked build of SCIP. However, it only includes SCIP with
SoPlex so can only handle linear constraints.

### Custom SCIP installation

If no feature is not enabled, `russcip` will look for a scip installation in the current conda environment,
to install SCIP using conda run the following command

```bash
conda install --channel conda-forge scip
```

Alternatively, you can specify the installation directory through the `SCIPOPTDIR` environment variable.

*russcip* is tested against SCIP 9.0.0 but it might work for other versions depending on which functionality you use.

### Examples

An [example](examples/create_and_solve.rs) on how to model and solve an integer program can be found in
the [examples](examples) directory.
To run the example, you can use the following command

```bash
cargo run --example create_and_solve
```

## Accessing unsafe functions

The `ffi` module provides access to the raw C-API of SCIP. This can be used to call functions that are not wrapped in
the safe interface yet.
The `scip_ptr` unsafe function in the `Model` struct, which gives you access to the underlying SCIP raw pointer.
Each other wrapper struct has a similar function named `inner`, e.g. `Variable::inner` or `Constraint::inner` gives you
a `*mut ffi::SCIP_VAR` or `*mut ffi::SCIP_CONS` respectively.

## Implementing Custom Plugins

Some of SCIP's plugins are imported to the rust interface as traits. Currently the implemented plugins are:

| **Name** | **File** | **Docs** |
|------------------|---------------------------------------------------------------------------------|---------------------------------------------------------------------------------|
| Branching rule | [branchrule.rs](https://github.com/scipopt/russcip/blob/main/src/branchrule.rs) | [docs](https://docs.rs/russcip/latest/russcip/branchrule/trait.BranchRule.html) |
| Variable Pricer | [pricer.rs](https://github.com/scipopt/russcip/blob/main/src/pricer.rs) | [docs](https://docs.rs/russcip/latest/russcip/pricer/trait.Pricer.html) |
| Event Handler | [eventhdlr.rs](https://github.com/scipopt/russcip/blob/main/src/eventhdlr.rs) | [docs](https://docs.rs/russcip/latest/russcip/eventhdlr/trait.Eventhdlr.html) |
| Primal Heuristic | [heuristic.rs](https://github.com/scipopt/russcip/blob/main/src/heuristic.rs) | [docs](https://docs.rs/russcip/latest/russcip/eventhdlr/trait.Heuristic.html) |

To add a custom plugin to a SCIP `Model` instance, you should implement its trait and call the corresponding
`include_{PLUGIN_NAME}` method. For examples on implementing the specific plugin trait you can check the tests in the
corresponding files.

## Contributing

Thinking about contributing to _russcip_? First of all thank you! You can check our
issues [page](https://github.com/scipopt/russcip/issues), there's a bunch of [
_good_first_issues_](https://github.com/scipopt/russcip/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22),
or you can check our contribution [guide](CONTRIBUTING.md). If you'd like to contribute and unsure what to do, or
thinking about a big feature and want to discuss if it makes sense and what is the best way to do it? you could open a
new [issue](https://github.com/scipopt/russcip/issues/new/choose)/[discussion](https://github.com/scipopt/russcip/discussions/new/choose)
or send me a quick email [@mmghannam](https://github.com/mmghannam).

## About SCIP

SCIP is currently one of the fastest non-commercial solvers for mixed integer programming (MIP) and mixed integer
nonlinear programming (MINLP). It is also a framework for constraint integer programming and branch-cut-and-price. It
allows for total control of the solution process and the access of detailed information down to the guts of the solver.