# DepSelectorLibgecode

This library vendors Gecode 3.7.3 as a rubygem so it can easily be used
with the [dep-selector](https://github.com/opscode/dep-selector)
project.

[Gecode](http://www.gecode.org) is a fast CSP solver library written in
C++. We created this library to install it in order to optimize the
following criteria:
* Allow users to install libraries that depend on gecode without extra
steps.
* Install the correct version of gecode for dep-selector. The current
release line of gecode is 4.x, but dep-selector uses ~> 3.5.
* Configure the source installation for shortest compilation time by
excluding unnecessary components. Gecode has a reputation for taking a
long time to compile, but in fact most of that time is spent building
examples and documentation. We've disabled these, along with the
flatzinc interpreter.

## Installation

Add this line to your application's Gemfile:

    gem 'dep-selector-libgecode'

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install dep-selector-libgecode

## Installation on Windows

* The recommended installation method is
  [ChefDK](https://downloads.chef.io/chef-dk/windows/#/) and the following
  steps can be skipped if you choose this method.
* Don't set `USE_SYSTEM_GECODE` to anything. The build only checks for the
  presence of this variable, not the value.
* Install [ruby](http://rubyinstaller.org/downloads/). Install
  [DevKit](http://rubyinstaller.org/add-ons/devkit/)(preferred), or install
  [mingw](http://sourceforge.net/projects/mingw/files/) and add it to your
  PATH. You can use the Chef omnibus MSI to get a working ruby and devkit.
* Install a working tar, and include it in your PATH. There is a tar binary
  that comes with the git package, but it is horribly broken and only good for
  generating core dumps. Before you build anything check `where tar` to make sure
  the tar from git is not the first one in your PATH. The chef-client omnibus
  package has a tar that works (easiest), or you can get one from here:
  http://gnuwin32.sourceforge.net/packages/gtar.htm
* `gem install berkshelf` should work now.
* Examples for automating these builds can also be found at
  [omnibus-chef](https://github.com/opscode/omnibus-chef) and
  [omnibus-software](https://github.com/opscode/omnibus-software).

### Requirements

This gem runs make with concurrent jobs to speed build time, so it uses
about 2GB of RAM during the build. If this doesn't work for your
environment, see 'Using a System Gecode Instead' below. Better yet, if
you only want to install Berkshelf, try using
[ChefDK](http://www.getchef.com/downloads/chef-dk) instead of a gem
install.

### Using a System Gecode Instead

Use the "USE_SYSTEM_GECODE" environment variable when installing to
make dep-selector-libgecode use the system version, instead of
downloading the source and building its own copy:

    $ USE_SYSTEM_GECODE=1 gem install dep-selector-libgecode

*WARNING:* Ensure that your system packages provide Gecode version 3 and
not version 4. Version 4 does not work with dep-selector.

## Usage

`DepSelectorLibgecode` provides helper functions for locating the
vendored gecode after installation:

```ruby
require 'dep-selector-libgecode'

# The vendored lib dir:
DepSelectorLibgecode.opt_path

# The include dir (where the headers are):
DepSelectorLibgecode.include_path
```

## Licensing

The packaging code here is released under the terms of the Apache2
license. Gecode itself is released under the terms of the MIT license.

See CONTRIBUTING.md for more information.

## Contributing

See CONTRIBUTING.md for more information.