Radixor/docs/benchmarks/languages/german.md

German Stemmer Benchmarks

This page reports same-language stemming benchmarks for German. Accuracy is listed first because speed without root agreement is not enough to interpret stemmer quality.

All speed values are environment-specific and were measured on the hardware and JVM listed in the benchmark overview. Speed benchmark operations process changed dictionary tokens only. Accuracy uses the complete Radixor dictionary for the language.

Radixor must not be read as simply "slower" when a narrow competitor has a lower timing row. In these tables Radixor is the quality-oriented baseline: its exact-root accuracy is typically close to 100%, while many faster rule-based, light, minimal, or possessive filters reach that speed by doing much less linguistic work and often score far lower in All exact and Changed exact. The Radixor rows in this benchmark refresh use the contracted compiled patch trie: compilation collapses uniform patch-command subtrees into accepting leaves, reducing hot lookup depth while preserving the preferred stemming result measured by the accuracy pass. The EnglishRadixorDictionaryCoverageBenchmark table shows the resulting quality/speed envelope explicitly. The same interpretation applies to this language page: speed rows must be read together with the accuracy table above them.

Dictionary Corpus

Resource	Dictionary rows	Complete quality tokens	Already-root tokens	Changed speed tokens
DE_DE	39,315	213,440	73,799	139,641

Radixor Patch Command Distribution

Radixor stores the preferred transformation for each normalized dictionary word form as a compiled patch command. This distribution shows which runtime command class is selected by the trained trie for the complete language dictionary. The total number of preferred patch commands analyzed for this language is 213,440.

Command class	Meaning	Word forms	Share
AppendCharacterCommand	Appends one character to the end of the word form.	3,627	1.699%
BackwardCompoundCommand	Applies a multi-step backward patch made from skip, delete, insert, and replace operations.	48,605	22.772%
DeleteSuffixCommand	Deletes one or more trailing characters from the word form.	80,443	37.689%
PreserveCommand	Returns the word form unchanged because it already matches the preferred root.	75,717	35.475%
ReplaceLastCharacterCommand	Replaces the final character of the word form.	5,048	2.365%

Accuracy

Accuracy is computed from one deterministic JMH measurement iteration without warmup. The benchmark may execute the full dictionary pass more than once inside that single timed iteration; percentages divide matching counters by evaluated counters from the same iteration.

Stemmer	All exact	Changed exact	Root preserved	Note
Radixor	97.455%	97.973%	96.476%	Full Radixor dictionary patch-command stemmer.
Lucene GermanLightStemFilter	38.583%	35.800%	43.849%	Light suffix stemmer; intentionally narrower than a dictionary-derived stemmer.
Lucene GermanMinimalStemFilter	37.492%	38.538%	35.513%	Minimal suffix reducer; narrow baseline, not a full stemmer.
Lucene SnowballFilter	33.380%	30.939%	37.999%	Lucene TokenFilter integration path around the Snowball algorithm.
Official Snowball direct	32.863%	31.225%	35.963%	Official Snowball generated Java stemmer; rule-based suffix algorithm.
Lucene GermanStemFilter	26.168%	24.979%	28.416%	German Lucene stemming TokenFilter; broader than minimal/light variants.

Speed

Speed uses JMH average time, 3 warmup iterations, 5 measurement iterations, 1 fork, and 1 thread. Relative factor is computed against the single Radixor row on this language page. Values below 1.000 are faster than that Radixor baseline; values above 1.000 are slower.

Stemmer	Benchmark method	Score ms/op	Error ms	ns/token	Relative vs Radixor	Note
Radixor	germanRadixor	9.518	0.338	68.2	1.000	Full Radixor dictionary patch-command stemmer.
Lucene GermanMinimalStemFilter	germanLuceneGermanMinimalStemFilter	12.020	0.460	86.1	1.263	Minimal German suffix reduction; narrow baseline.
Lucene GermanLightStemFilter	germanLuceneGermanLightStemFilter	12.413	1.059	88.9	1.304	Light German suffix stemmer; narrower than a dictionary stemmer.
Lucene GermanStemFilter	germanLuceneGermanStemFilter	36.644	5.667	262.4	3.850	Older German stemming TokenFilter with normalization requirements.
Lucene SnowballFilter	luceneSnowballFilter[GERMAN]	54.846	8.710	392.8	5.762	Lucene TokenFilter path around Snowball; includes TokenStream overhead.
Official Snowball direct	snowballDirect[GERMAN]	52.974	7.989	379.4	5.566	Official Snowball generated Java stemmer; direct API.

Interpretation Notes

• Radixor is a dictionary-derived patch-command stemmer. Its quality depends on the language resource used to train the compiled trie.
• Light, minimal, plural, and possessive filters are narrow baselines. They can be fast because they intentionally perform less linguistic work.
• Lucene TokenFilter rows include TokenStream, attribute, and required normalization overhead. Direct rows measure exposed direct APIs.
• Morfologik rows are dictionary-based and can emit multiple terms for one input token. Quality rows use the first returned term when no ranking weight is available.
• Snowball rows are rule-based generated suffix stemmers; they are useful algorithmic baselines, not dictionary-root equivalence guarantees.