Skip to content


Repository files navigation


Gem Version Build Status

A Ruby versioning constraint solver implementing Semantic Versioning 2.0.0.


$ gem install solve


Create a new graph

graph =

Add an artifact to the graph

graph.artifact("nginx", "1.0.0")

Now add another artifact that has a dependency

graph.artifact("mysql", "1.2.4-alpha.1").depends("openssl", "~> 1.0.0")

Dependencies can be chained, too

graph.artifact("ntp", "1.0.0").depends("build-essential").depends("yum")

And now solve the graph with some demands!(graph, [['nginx', '>= 0.100.0']])

Or, if you want a topologically sorted solution NOTE: This will raise Solve::Errors::UnsortableSolutionError if the solution contains a cycle (which can happen with ruby packages)!(graph, [['nginx', '>= 0.100.0']], sorted: true)

Selecting A Resolver

Solve supports two different resolvers. A pure Ruby solver implemented using Molinillo and the same dependency resolver the Chef Server uses, dep-selector, which is a Ruby C extension for Gecode.

You can set the resolver by calling Solve.engine= with the symbol :ruby or :gecode.

Solve.engine = :ruby
Solve.engine = :gecode

The Ruby solver is installed and enabled by default. If you'd like to use the Gecode solver you can do so by installing the dep-selector gem or adding it to your Gemfile:

$ gem install dep_selector

Increasing the solver's timeout

By default the solver will wait 30 seconds before giving up on finding a solution. Under certain conditions a graph may be too complicated to solve within the alotted time. To increase the timeout you can set the "SOLVE_TIMEOUT" environment variable to the amount of seconds desired.

$ export SOLVE_TIMEOUT=60

This will set the timeout to 60 seconds instead of the default 30 seconds.