Radixor

Fast algorithmic stemming with compact patch-command tries — measured at about 4× to 6× the throughput of the Snowball Porter stemmer family on the current English benchmark workload.

Radixor is a fast, algorithmic stemming toolkit for Java, built around compact patch-command tries in the tradition of the original Egothor stemmer.

On the current JMH English comparison benchmark, Radixor with bundled US_UK_PROFI reaches approximately 31 to 32 million tokens per second, compared with about 8 million tokens per second for Snowball original Porter and about 5 to 5.5 million tokens per second for Snowball English (Porter2).

That means the current Radixor implementation is approximately:

• 4× faster than Snowball original Porter
• 6× faster than Snowball English (Porter2)

It is designed for production search and text-processing systems that need stemming which is:

• fast at runtime
• compact in memory and on disk
• deterministic in behavior
• driven by dictionary data rather than hardcoded language rules
• practical to maintain, extend, and test

Radixor keeps the valuable core of the original Egothor idea, modernizes the implementation, and adds capabilities that make it more useful in real software systems today.

Table of Contents

• Why Radixor
• Heritage
• What Radixor adds
• Key features
• Performance
• Documentation
• Project philosophy
• Historical note

Why Radixor

The central idea behind Radixor is simple: learn how to transform a word form into its stem, encode that transformation as a compact patch command, store it in a trie, and make runtime lookup extremely fast.

This gives you a stemmer that is:

• data-driven rather than rule-hardcoded
• reusable across languages
• compact enough for deployment-friendly binary artifacts
• suitable for both offline compilation and runtime loading

Radixor is especially attractive when you want something more adaptable than simple suffix stripping, but much smaller and easier to operate than a full morphological analyzer. In the current English benchmark comparison against the Snowball Porter stemmer family, it also delivers a substantial throughput advantage.

Heritage

Radixor stands in the line of the original Egothor stemming work and its later Stempel packaging.

Historical Stempel documentation describes the stemmer code as taken virtually unchanged from the Egothor project, and Elasticsearch still documents the Stempel analysis plugin as integrating Lucene’s Stempel module for Polish.

Useful historical references:

• Egothor project
• Stempel overview
• Lucene Stempel overview
• Elasticsearch Stempel plugin

Radixor is not just a repackaging of legacy code. It is a practical modernization of the approach for current Java development and long-term maintainability.

What Radixor adds

Radixor keeps the patch-command trie model, but improves the engineering around it.

Compared with the historical baseline, Radixor emphasizes:

• simplification to the most practical core
  The implementation focuses on the parts of the original approach that are most useful in production.

• immutable compiled tries
  Runtime lookup uses compact read-only structures optimized for efficient access.

• support for more than one stemming result
  Radixor can expose both a preferred result and multiple candidate results where the data is ambiguous.

• frequency-aware deterministic ordering
  Candidate results are ordered consistently and reproducibly.

• practical subtree reduction modes
  Reduction can be tuned toward stronger compression or more conservative behavioral preservation.

• reconstruction of writable builders from compiled tables
  Existing compiled stemmer tables can be reopened, modified, and compiled again.

• better tests and implementation stability
  Stronger coverage improves confidence during refactoring and further development.

Key features

• Fast algorithmic stemming
• Compact compiled binary artifacts
• Patch-command based transformation model
• Dictionary-driven language adaptation
• Single-result and multi-result lookup
• Deterministic result ordering
• Compressed binary persistence
• Programmatic compilation and loading
• CLI compilation tool
• Bundled language resources
• Support for extending compiled stemmer tables

Performance

Radixor includes a JMH benchmark suite for both its own algorithmic core and a side-by-side comparison against the Snowball Porter stemmer family.

On the current English comparison workload, Radixor with bundled US_UK_PROFI reaches approximately 31 to 32 million tokens per second. Snowball original Porter reaches approximately 8 million tokens per second, and Snowball English (Porter2) approximately 5 to 5.5 million tokens per second.

That places Radixor at approximately 4× the throughput of Snowball original Porter and approximately 6× the throughput of Snowball English (Porter2) on the current benchmark workload.

This is a throughput comparison on the same deterministic token stream. It is not a claim that the compared stemmers are linguistically equivalent or interchangeable.

For benchmark scope, workload design, environment, commands, report locations, and interpretation guidance, see Benchmarking.

Documentation

The repository keeps the front page concise and places detailed documentation under docs/.

Start here:

• Quick Start
  A practical first guide to loading, compiling, and using Radixor.

• Dictionary Format
  How to write stemming dictionaries.

• Compilation (CLI tool)
  How to compile dictionaries with the Compile CLI.

• Programmatic Usage
  How to build, load, modify, and query Radixor from Java code.

• Built-in Languages
  How to use integrated language resources such as US_UK_PROFI.

• Architecture and Reduction
  Internal model, compiled trie design, and reduction strategies.

• Quality and Operations
  Testing, persistence, deployment, and operational guidance.

• Benchmarking
  JMH benchmark design, Snowball comparison, execution, and interpretation.

Project philosophy

Radixor does not preserve historical complexity for its own sake.

It preserves the valuable idea:

• compact learned transformations
• trie-based lookup
• language-data driven stemming
• practical runtime speed

Then it improves the parts modern users care about:

• maintainability
• testability
• modification workflows
• persistence
• determinism
• clearer APIs

The goal is to keep the Egothor/Stempel lineage useful as a serious contemporary software component.

Historical note

Egothor showed that stemming could be both algorithmic and compact. Stempel proved that the approach was practical enough to survive inside major search ecosystems. Radixor continues that tradition with a modernized implementation focused on production use, maintainability, and controlled evolution.