cljgrapht

An idiomatic Clojure graph library backed by JGraphT: build graphs over plain Clojure values and run JGraphT's fast, mature algorithm catalog, getting plain Clojure data back.

Stack

Why

Graph work is the textbook case where Python's networkx is slow: it's pure Python, and graph algorithms are irregular and pointer-chasing, so they never vectorize into a C core the way numpy workloads do. On the JVM the same algorithms run on JIT-compiled code with real threads.

loom and ubergraph are the established pure-Clojure graph libraries, and if they cover your needs they're a great fit. cljgrapht takes a different tack: instead of implementing algorithms in Clojure, it wraps JGraphT, so you get its large, actively-developed algorithm catalog (shortest paths, centrality, flow, matching, coloring, isomorphism, and more) running on the JVM, behind a Clojure-shaped API. Reach for it when you want an algorithm the pure-Clojure libraries don't ship, or JGraphT's performance on large graphs. Vertices are any Clojure value; results come back as vectors, sets, and maps.

This is a performance wrapper, not a persistent data structure: graphs are JGraphT's native mutable objects. Constructors and mutators return the graph for threading, but they mutate in place.

Requires JDK 11+ (JGraphT 1.5.x).

Install

Leiningen (project.clj):

[net.clojars.savya/cljgrapht "0.1.1"]

tools.deps (deps.edn):

net.clojars.savya/cljgrapht {:mvn/version "0.1.1"}

Usage

(require '[cljgrapht.core :as g]
         '[cljgrapht.algo :as a])

;; Build a weighted directed graph from edge data.
(def road
  (g/weighted-digraph [[:a :b 1.0] [:a :c 4.0] [:b :c 1.0] [:c :d 1.0]]))

;; Cheapest route, as Clojure data.
(a/shortest-path road :a :d)
;; => {:path [:a :b :c :d] :weight 3.0}

;; Undirected social graph; who is most central?
(def social (g/graph [[:alice :bob] [:bob :carol] [:bob :dave] [:carol :dave]]))

(a/betweenness-centrality social)
;; => {:alice 0.0 :bob 2.0 :carol 0.0 :dave 0.0}

;; Dependency graph: order tasks, or detect a cycle.
(def deps (g/digraph [[:compile :test] [:compile :package] [:test :deploy]
                      [:package :deploy]]))

(a/topological-sort deps) ;; => [:compile :test :package :deploy]
(a/cycle? deps)           ;; => false

What's in cljgrapht.algo

• Shortest paths: shortest-path, shortest-path-length, all-pairs-shortest-path-length
• Connectivity: connected-components, strongly-connected-components
• Ordering & cycles: topological-sort, cycle?, vertices-on-cycles
• Spanning: minimum-spanning-tree
• Centrality: betweenness-centrality, closeness-centrality, pagerank

License

Copyright © 2026 Savya Sachi Jha

Distributed under the Eclipse Public License 2.0, the same license JGraphT is available under.