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core.rrb-vector

Why would anyone want to use this library? The two primary answers are:

  • You want faster concatenation of vectors, which core.rrb-vector's catvec function provides for both Clojure and ClojureScript.
  • You use vectors of Java primitive types like long, double, etc., returned by Clojure's vector-of function, e.g. to reduce memory usage to about 1/3 of the memory required by vectors of arbitrary objects, and
    • You want the speed enabled by using the transient versions of such vectors. Clojure does not implement transients for primitive vectors created via vector-of -- core.rrb-vector does.

Vectors are one of the most commonly used data structures within Clojure. Likely you already know that creating a vector equal to v plus a new element e appended to the end using the expression (conj v e) has a run time that is "effectively constant", i.e. it takes O(log N) time in the size N of v, where the base of the logarithm is 32, so it is a constant at most 4 for all vector sizes up to a million, and at most 7 for all vector sizes that Clojure supports.

The fastest way to concatenate two vectors v1 and v2 into a single new vector is using an expression like (into v1 v2). This is implemented by repeatedly appending a single element from the second vector to the first, so it takes linear time in the size of v2 (multiplied by the effectively constant time mentioned above).

Aside: There might be another expression that has a better constant factor for its run time than (into v1 v2) does, and is thus faster. However, any other such expression will still take at least linear time in the size of the second vector.

The core.rrb-vector library uses a tree structure similar to the one that Clojure uses internally for vectors, but generalizes it in such a way that producing a new tree that represents the concatenation of two input vectors using the catvec function can be done in O(log N) time, where N is the size of the result.

You can give catvec vectors created in all of the ways you already normally do, and while it will return a new type of object, this new type behaves in all of the ways you expect a Clojure vector to behave. This new type of vector is indistinguishable from a normal Clojure vector unless you examine the value of (type v) or (class v). In particular, (vector? v) is true for this new type, you can call all of the usual sequence-based functions on it to examine or process its elements, you can call conj on it, nth, etc.

Thus if you have a program where frequently concatenating large vectors to produce new vectors is useful, core.rrb-vector may help you write a much faster program in a more natural way.

This library is an implementation of the confluently persistent vector data structure introduced in the paper "RRB-Trees: Efficient Immutable Vectors", EPFL-REPORT-169879, September, 2011, by Phil Bagwell and Tiark Rompf.

RRB-Trees build upon Clojure's internal PersistentVector class used to implement its built in vectors, adding logarithmic time concatenation and slicing (i.e. create sub-vectors from input vectors). ClojureScript is supported with the same API, except for the absence of the vector-of function.

The main functions provided are clojure.core.rrb-vector/catvec, performing vector concatenation, and clojure.core.rrb-vector/subvec, which produces a new vector containing the appropriate subrange of the input vector (in contrast to clojure.core/subvec, which returns a view on the input vector).

Like Clojure vectors, core.rrb-vector vectors can store arbitrary values, or using vector-of you can create vectors restricted to one primitive type, e.g. long, double, etc. The core.rrb-vector implementation provides seamless interoperability with the built in Clojure vectors of class clojure.lang.PersistentVector, clojure.core.Vec (vectors of primitive values) and clojure.lang.APersistentVector$SubVector instances: clojure.core.rrb-vector/catvec and clojure.core.rrb-vector/subvec convert their inputs to clojure.core.rrb_vector.rrbt.Vector instances whenever necessary (this is a very fast constant time operation for PersistentVector and primitive vectors; for SubVector it is O(log N), where N is the size of the underlying vector).

clojure.core.rrb-vector also provides its own versions of vector, vector-of, and vec that always produce clojure.core.rrb_vector.rrbt.Vector instances. Note that vector-of accepts :object as one of the possible type arguments, in addition to keywords naming primitive types.

Usage

core.rrb-vector exports one public namespace:

(require '[clojure.core.rrb-vector :as fv])

Note that the ClojureScript version uses the same namespace name (it does not use the alternative cljs.* prefix!). This is because the API is precisely the same (except clojure.core.rrb-vector/vector-of only makes sense on the JVM and is therefore not available in ClojureScript).

The docstring attached to the namespace provides an overview of the available functionality (as found at the top of this README):

(doc clojure.core.rrb-vector)

The new functionality is accessible through two functions: clojure.core.rrb-vector/subvec, which provides logarithmic-time non-view slicing (in contrast to clojure.core/subvec, which is a constant-time operation producing view vectors that prevent the underlying vector from becoming eligible for garbage collection), and clojure.core.rrb-vector/catvec, which provides logarithmic-time concatenation. Crucially, these can be applied to regular Clojure(Script) vectors.

(doc fv/subvec)
(doc fv/catvec)

;; apply catvec and subvec to regular Clojure(Script) vectors
(fv/catvec (vec (range 1234)) (vec (range 8765)))
(fv/subvec (vec (range 1024)) 123 456)

Additionally, several functions for constructing RRB vectors are provided. There is rarely any reason to use them, since, as mentioned above, the interesting functions exported by core.rrb-vector work with regular vectors. Note that clojure.core.rrb-vector/vec, in contrast to clojure.core/vec, reuses the internal tree of its input if it already is a vector (of any type) and does not alias short arrays. When passed a non-vector argument, it returns an RRB vector.

(doc fv/vector)
(doc fv/vector-of)
(doc fv/vec)

The debug namespace bundled with core.rrb-vector provides several utilities used by the test suite, as well as a function for visualizing the internal structure of vectors that works with regular Clojure(Script) vectors and RRB vectors.

;; for peeking under the hood
(require '[clojure.core.rrb-vector.debug :as dv])
(dv/dbg-vec (fv/catvec (vec (range 1234)) (vec (range 8765))))

Releases and dependency information

core.rrb-vector requires Clojure >= 1.5.0. View vectors created by clojure.core/subvec are correctly handled for Clojure >= 1.6.0. The ClojureScript version is regularly tested against the most recent ClojureScript release.

core.rrb-vector releases are available from Maven Central. Development snapshots are available from the Sonatype OSS repository.

Follow the first link above to discover the current release number.

Leiningen dependency information:

[org.clojure/core.rrb-vector "${version}"]

Maven dependency information:

<dependency>
  <groupId>org.clojure</groupId>
  <artifactId>core.rrb-vector</artifactId>
  <version>${version}</version>
</dependency>

Gradle dependency information:

compile "org.clojure:core.rrb-vector:${version}"

TODO

  1. more tests;

  2. performance: general perf tuning, more efficient catvec implementation (to replace current seq-ops-based impl).

Developer information

core.rrb-vector is being developed as a Clojure Contrib project, see the What is Clojure Contrib page for details. Patches will only be accepted from developers who have signed the Clojure Contributor Agreement.

Useful Maven commands

To run Clojure and ClojureScript tests:

$ mvn -DCLOJURE_VERSION=1.10.1 -Dclojure.version=1.10.1 clean test

Clojure versions as old as 1.5.1 can be tested with such a command, but the ClojureScript tests only work when using Clojure 1.8.0 or later.

To run tests and, if successful, create a JAR file in the targets directory:

$ mvn -DCLOJURE_VERSION=1.10.1 -Dclojure.version=1.10.1 clean package

Prerequisites: Only Java and Maven need to be installed. Maven will download whatever versions of Clojure are needed for the command you use. Both Clojure and ClojureScript tests are run with the commands given here. They use the Nashorn JavaScript run time environment included with Java -- no other JavaScript run time is needed.

Useful clj CLI commands

To run relatively short Clojure tests, but no ClojureScript tests:

$ ./script/jdo test

To run relatively short ClojureScript tests, but no Clojure tests:

$ ./script/sdo test

Warning: Currently the command above for running ClojureScript tests does not show warnings from the ClojureScript compiler. I have seen some ClojureScript compiler warnings appear when running the Maven command above, and the Leiningen command given below for running ClojureScript tests, that unfortunately do not appear using ./script/sdo test. Suggestions welcome on how to make that command also show similar warnings.

Replace test in the commands above with one of the following for other useful things:

  • sock (or no argument at all) - start a REPL, and listen for a socket REPL connection on TCP port 50505
  • long - run a longer set of tests
  • coll - run generative tests from collection-check library
  • east - run Eastwood lint tool (clj version only, not cljs)

Useful Leiningen commands

To run Clojure tests, but no ClojureScript tests:

$ lein with-profile +1.10 test

You can test with Clojure versions 1.5 through 1.10 by specifying that version number after the +.

Prerequisites: Only Java and Leiningen. Leiningen will download whatever versions of Clojure and other libraries are needed.

To run ClojureScript tests with Node.js and SpiderMonkey JavaScript runtimes, but no Clojure tests:

$ lein with-profile +cljs cljsbuild test

Add node or spidermonkey as a separate argument after test to restrict the JavaScript runtime used to only the one you specify. You may need to adjust the command names in the :test-commands section of the project.clj file if the command for running those JavaScript runtimes have a different name on your system than what is used there.

Prerequisites: Java, Leiningen, and either or both of Node.js and SpiderMonkey JavaScript run time environments.

To run normal Clojure tests, plus the collection-check tests, but no ClojureScript tests:

$ lein with-profile +coll,+1.7 test

The collection-check tests require Clojure 1.7.0 or later, I believe because collection-check and/or its dependencies require that.

There is no existing command configured to run collection-check tests with ClojureScript.

To start a REPL from Leiningen with Clojure versions 1.6.0 and older, you must use Leiningen 2.8.0 (likely some other versions work, too).

Installing other software you will need

For all of the development commands you must have Java installed. This includes the ClojureScript compile and test commands, since the ClojureScript compiler is at least partially written in the Java version of Clojure.

Java

Install one or more of the pre-built binaries from AdoptOpenJDK, or several other providers of Java binaries.

Additional methods:

  • Ubuntu 18.04 Linux: sudo apt-get install default-jre

Maven

For any mvn command you must install Maven.

  • Ubuntu 18.04 Linux: sudo apt-get install maven
  • macOS
    • plus Homebrew: brew install maven
    • plus MacPorts: sudo port install maven3, then either use the command mvn3, or to use mvn also run the command sudo port select --set maven maven3.

Leiningen

An install script and instructions are available on the Leiningen site.

Node.js JavaScript run time environment

Installation instructions for many different versions of Node.js are available on the Node.js web site. You can also install it using the commands below.

  • Ubuntu 18.04 Linux: sudo apt-get install nodejs
  • macOS
    • plus Homebrew: brew install node
    • plus MacPorts: sudo port install nodejs10. You can see other versions available via the command port list | grep nodejs.

SpiderMonkey JavaScript run time environment

Installation instructions for many different versions of SpiderMonkey are available on the SpiderMonkey web site. You may also install it using the commands below.

  • Ubuntu 18.04 Linux: sudo apt-get install libmozjs-52-dev
  • macOS
    • plus Homebrew: As of 2019-Sep-24, brew install spidermonkey installs version 1.8.5 of SpiderMonkey, which according to the Wikipedia page on SpiderMonkey was first released in 2011, with at least one release per year after that. The ClojureScript tests fail to run using this version of SpiderMonkey. It seems worth avoiding this version of SpiderMonkey for the purposes of testing core.rrb-vector.
    • plus MacPorts: sudo port install mozjs52

Clojure(Script) code reuse

core.rrb-vector's vectors support the same basic functionality regular Clojure's vectors do (with the omissions listed above). Where possible, this is achieved by reusing code from Clojure's gvec and ClojureScript's PersistentVector implementations. The Clojure(Script) source files containing the relevant code carry the following copyright notice:

Copyright (c) Rich Hickey. All rights reserved.
The use and distribution terms for this software are covered by the
Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
which can be found in the file epl-v10.html at the root of this distribution.
By using this software in any fashion, you are agreeing to be bound by
  the terms of this license.
You must not remove this notice, or any other, from this software.

Licence

Copyright © 2012-2019 Michał Marczyk, Andy Fingerhut, Rich Hickey and contributors

Distributed under the Eclipse Public License 1.0, the same as Clojure. The licence text can be found in the epl-v10.html file at the root of this distribution.

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