Comprehensive Research Report & Full Ablation Study
This repository contains NLP models trained and evaluated by Wikilangs, specifically on Central Kanuri Wikipedia data.
We analyze tokenizers, n-gram models, Markov chains, vocabulary statistics, and word embeddings.
📋 Repository Contents
Models & Assets
Tokenizers (8k, 16k, 32k, 64k)
N-gram models (2, 3, 4, 5-gram)
Markov chains (context of 1, 2, 3, 4 and 5)
Subword N-gram and Markov chains
Embeddings in various sizes and dimensions (aligned and unaligned)
Sample 3:Nasionalism dǝ shima raayi-a letǝgǝ-a do lardǝ-a lardǝ-a kalkalzǝyinma.
Vocab
Tokens
Count
8k
▁nas ional ism ▁dǝ ▁shima ▁raayi - a ▁letǝgǝ - ... (+12 more)
22
16k
▁nas ional ism ▁dǝ ▁shima ▁raayi - a ▁letǝgǝ - ... (+12 more)
22
32k
▁nas ional ism ▁dǝ ▁shima ▁raayi - a ▁letǝgǝ - ... (+11 more)
21
64k
▁nasionalism ▁dǝ ▁shima ▁raayi - a ▁letǝgǝ - a ▁do ... (+8 more)
18
Key Findings
Best Compression: 64k achieves 4.582x compression
Lowest UNK Rate: 8k with 0.1074% unknown tokens
Trade-off: Larger vocabularies improve compression but increase model size
Recommendation: 32k vocabulary provides optimal balance for production use
2. N-gram Model Evaluation
N-gram Perplexity
N-gram Unique
N-gram Coverage
Results
N-gram
Variant
Perplexity
Entropy
Unique N-grams
Top-100 Coverage
Top-1000 Coverage
2-gram
Word
4,001
11.97
9,862
23.1%
50.6%
2-gram
Subword
249 🏆
7.96
1,869
69.4%
99.6%
3-gram
Word
4,817
12.23
9,468
19.5%
45.2%
3-gram
Subword
1,863
10.86
14,091
29.8%
74.9%
4-gram
Word
8,323
13.02
14,018
13.9%
34.8%
4-gram
Subword
8,691
13.09
63,398
15.4%
45.6%
5-gram
Word
5,619
12.46
8,921
15.5%
38.8%
5-gram
Subword
24,681
14.59
137,201
10.0%
30.6%
Top 5 N-grams by Size
2-grams (Word):
Rank
N-gram
Count
1
saa lan
2,887
2
suro saa
2,636
3
bǝ lan
1,942
4
a kuru
1,725
5
ye lan
1,254
3-grams (Word):
Rank
N-gram
Count
1
suro saa lan
836
2
suro saa yen
549
3
lan suro saa
420
4
duwun yar laarrin
401
5
saa duwun yar
373
4-grams (Word):
Rank
N-gram
Count
1
saa duwun yar laarrin
356
2
bǝ lan suro saa
289
3
saa lan səta ro
279
4
lan səta ro saadənan
266
5
suro saa duwun yar
259
5-grams (Word):
Rank
N-gram
Count
1
saa lan səta ro saadənan
250
2
suro saa duwun yar laarrin
246
3
lan suro saa duwun yar
226
4
bǝ lan suro saa duwun
215
5
lan sun nzu notuna ma
147
2-grams (Subword):
Rank
N-gram
Count
1
a _
90,022
2
_ k
60,586
3
_ s
55,437
4
a n
52,900
5
e _
48,288
3-grams (Subword):
Rank
N-gram
Count
1
y e _
25,215
2
r o _
22,904
3
_ l a
22,653
4
l a n
19,693
5
_ k ə
17,814
4-grams (Subword):
Rank
N-gram
Count
1
_ k u r
14,890
2
_ l a n
13,928
3
_ s h i
12,446
4
l a n _
12,391
5
u r o _
10,490
5-grams (Subword):
Rank
N-gram
Count
1
_ l a n _
10,158
2
_ k u r u
9,916
3
k u r u _
9,220
4
_ s a a _
8,034
5
_ s u r o
7,792
Key Findings
Best Perplexity: 2-gram (subword) with 249
Entropy Trend: Decreases with larger n-grams (more predictable)
Coverage: Top-1000 patterns cover ~31% of corpus
Recommendation: 4-gram or 5-gram for best predictive performance
3. Markov Chain Evaluation
Markov Entropy
Markov Contexts
Markov Branching
Results
Context
Variant
Avg Entropy
Perplexity
Branching Factor
Unique Contexts
Predictability
1
Word
0.7789
1.716
4.96
48,641
22.1%
1
Subword
1.1205
2.174
7.93
642
0.0%
2
Word
0.2394
1.180
1.52
239,982
76.1%
2
Subword
0.9246
1.898
5.50
5,088
7.5%
3
Word
0.0706
1.050
1.11
362,994
92.9%
3
Subword
0.8154
1.760
3.92
27,951
18.5%
4
Word
0.0242 🏆
1.017
1.04
402,605
97.6%
4
Subword
0.6137
1.530
2.57
109,408
38.6%
Generated Text Samples (Word-based)
Below are text samples generated from each word-based Markov chain model:
Context Size 1:
a lardəwa asiabe sammaso stade mohammed goni shidə təlam romanbe kureye sun tzus military administra...
lan shiye bayanna kada ivan dychko a nabtə gomna malorossia ye askərra hutuyedə gozənadə tutsi kada
ye fimnzə səraanama zeland a halwa bəlin nankaro bakkada dunya bəlin gartəna shidoni ngawolan səta h...
Context Size 2:
saa lan washington college of the group of interparliamentary relations with the chevalier guard reg...
suro saa lan səta kəntawu marchye saa lan cotulowo kəntawu march saa acker yǝ bikke nəm sawa
bǝ lan suro nashawa league bǝ manchester city bǝ lan sun nzu notunaman sha chesambo yim fyakkin
Context Size 3:
suro saa lan shiga wakil majalis kuraye ro karrada loktu kərmai nigeria yǝ kən diyau medən gozə kowo...
suro saa yen loktu kura lardəye arturo umberto illia futu spanish lan bowotin kito r quechua kitu hu...
lan suro saa lan bərnidə wuratə saa woson kashi 11 5 səwandəna 9 futu razəwuye faraktənadən tubman y...
Context Size 4:
saa duwun yar laarrin findin laarrin bǝ lan kǝntawu razab bǝ lan suro saa duwun yar laarrin findin l...
bǝ lan suro saa duwun yar laarrin fitulurrin luko uwun bǝ lan sha katambo dekkel baktema cidi urugua...
saa lan səta ro saadənan demokradiyamen kura lardəye kartəro a saa 16 ro cidazəna kuru shima kamu ku...
Generated Text Samples (Subword-based)
Below are text samples generated from each subword-based Markov chain model:
Context Size 1:
_nandəbə_lainza_
awurso_kə_ku_dǝ.
niwobewo_sǝruwsə
Context Size 2:
a_ka_ko_aprey-zau
_kəriero;_shima_i
_surunyakkaradebe
Context Size 3:
ye_fro-a,_diodəna.
ro_kada_nəm_greef_
_lardero_suro_saa_
Context Size 4:
_kuru_nəmnzə-a_lan_
_lan,_bəladiya_lan_
_shima_lardə_bəlin_
Key Findings
Best Predictability: Context-4 (word) with 97.6% predictability
Branching Factor: Decreases with context size (more deterministic)
Memory Trade-off: Larger contexts require more storage (109,408 contexts)
Recommendation: Context-3 or Context-4 for text generation
4. Vocabulary Analysis
Zipf's Law
Top Words
Coverage Curve
Statistics
Metric
Value
Vocabulary Size
19,840
Total Tokens
415,541
Mean Frequency
20.94
Median Frequency
3
Frequency Std Dev
234.13
Most Common Words
Rank
Word
Frequency
1
a
19,508
2
lan
13,848
3
ye
10,032
4
kuru
9,262
5
saa
8,070
6
suro
7,134
7
də
5,746
8
bǝ
4,251
9
shima
3,927
10
ro
3,601
Least Common Words (from vocabulary)
Rank
Word
Frequency
1
rugbyye
2
2
brivero
2
3
chiefs
2
4
nuala
2
5
éireann
2
6
taghmon
2
7
seán
2
8
girton
2
9
ryandə
2
10
ucd
2
Zipf's Law Analysis
Metric
Value
Zipf Coefficient
1.1101
R² (Goodness of Fit)
0.993201
Adherence Quality
excellent
Coverage Analysis
Top N Words
Coverage
Top 100
42.1%
Top 1,000
70.5%
Top 5,000
88.4%
Top 10,000
94.5%
Key Findings
Zipf Compliance: R²=0.9932 indicates excellent adherence to Zipf's law
High Frequency Dominance: Top 100 words cover 42.1% of corpus
Long Tail: 9,840 words needed for remaining 5.5% coverage
5. Word Embeddings Evaluation
Embedding Isotropy
Similarity Matrix
t-SNE Words
t-SNE Sentences
5.1 Cross-Lingual Alignment
Alignment Quality
Multilingual t-SNE
5.2 Model Comparison
Model
Dimension
Isotropy
Semantic Density
Alignment R@1
Alignment R@10
mono_32d
32
0.7581
0.3263
N/A
N/A
mono_64d
64
0.3103
0.3195
N/A
N/A
mono_128d
128
0.0510
0.3146
N/A
N/A
aligned_32d
32
0.7581 🏆
0.3414
0.0460
0.2480
aligned_64d
64
0.3103
0.3156
0.0720
0.3240
aligned_128d
128
0.0510
0.3140
0.0860
0.4020
Key Findings
Best Isotropy: aligned_32d with 0.7581 (more uniform distribution)
Semantic Density: Average pairwise similarity of 0.3219. Lower values indicate better semantic separation.
Alignment Quality: Aligned models achieve up to 8.6% R@1 in cross-lingual retrieval.
Recommendation: 128d aligned for best cross-lingual performance
6. Morphological Analysis (Experimental)
This section presents an automated morphological analysis derived from the statistical divergence between word-level and subword-level models. By analyzing where subword predictability spikes and where word-level coverage fails, we can infer linguistic structures without supervised data.
6.1 Productivity & Complexity
Metric
Value
Interpretation
Recommendation
Productivity Index
5.000
High morphological productivity
Reliable analysis
Idiomaticity Gap
0.268
High formulaic/idiomatic content
-
6.2 Affix Inventory (Productive Units)
These are the most productive prefixes and suffixes identified by sampling the vocabulary for global substitutability patterns. A unit is considered an affix if stripping it leaves a valid stem that appears in other contexts.
Productive Prefixes
Prefix
Examples
-a
abrahamye, alao, awardsbe
-s
speaker, shawayen, saracenic
-b
beaumont, b3, bannazəna
-k
keryə, kəmbuzayin, kla
-m
manitobayen, maud, mukon
-ma
manitobayen, maud, magaji
-d
duro, dunyabewo, darajatin
-c
chaplin, crew, challenger
Productive Suffixes
Suffix
Examples
-e
zutəye, abrahamye, ukeje
-n
manitobayen, kəmbuzayin, chaplin
-a
kla, kəlanza, kaza
-ə
zamanbedə, keryə, kəzəkkə
-be
awardsbe, afghanistanbe, cathedralbe
-o
gowono, kadiwo, alao
-ye
zutəye, abrahamye, disembaye
-də
zamanbedə, kəradə, matədə
6.3 Bound Stems (Lexical Roots)
Bound stems are high-frequency subword units that are semantically cohesive but rarely appear as standalone words. These often correspond to the 'core' of a word that requires inflection or derivation to be valid.
Stem
Cohesion
Substitutability
Examples
zəna
1.88x
142 contexts
azəna, zazəna, lazəna
zana
1.90x
71 contexts
nozana, rozana, rizana
ardə
2.06x
25 contexts
lardə, gardə, lardəa
rmai
2.13x
21 contexts
kǝrmai, kirmai, kərmai
asha
1.85x
33 contexts
jasha, nasha, sasha
andi
1.60x
43 contexts
sandi, fandi, nandi
dəna
1.70x
31 contexts
dənan, tədəna, gadəna
ərma
2.00x
17 contexts
kərma, kərmai, kərmaro
lard
1.74x
23 contexts
lardə, lardu, larde
sand
1.73x
22 contexts
sandi, sanda, sandǝ
ambo
1.61x
21 contexts
tambo, kambo, dambo
nash
1.98x
11 contexts
nasha, nashaa, nashan
6.4 Affix Compatibility (Co-occurrence)
This table shows which prefixes and suffixes most frequently co-occur on the same stems, revealing the 'stacking' rules of the language's morphology.
Prefix
Suffix
Frequency
Examples
-k
-a
164 words
karewa, kazadalawa
-k
-e
142 words
kasattəbe, kungiyadəye
-k
-n
128 words
koktənadən, kǝrǝn
-k
-ə
120 words
kərmaitədə, kasuwudə
-a
-e
109 words
augustusbe, alcockye
-s
-n
96 words
smithsonian, sədin
-k
-o
87 words
kərazənaro, karəngaro
-s
-e
84 words
saharanye, samiye
-b
-a
82 words
bannatəma, bega
-b
-n
81 words
bernstein, baditənzən
6.5 Recursive Morpheme Segmentation
Using Recursive Hierarchical Substitutability, we decompose complex words into their constituent morphemes. This approach handles nested affixes (e.g., prefix-prefix-root-suffix).
Word
Suggested Split
Confidence
Stem
tǝdǝnaben
tǝdǝna-be-n
7.5
be
februaryben
february-be-n
7.5
be
generally
general-l-y
7.5
l
daurabedə
daura-be-də
7.5
be
beakerbedə
beaker-be-də
7.5
be
shaizarbedə
shaizar-be-də
7.5
be
africaben
africa-be-n
7.5
be
professorbero
professor-be-ro
7.5
be
kamuwaben
kamuwa-be-n
7.5
be
faidatanadə
faidata-na-də
7.5
na
kərgənbedə
kərgən-be-də
7.5
be
gargammabe
gargam-ma-be
7.5
ma
rinderpestbeye
rinderpest-be-ye
7.5
be
faidatinmawo
faidatin-ma-wo
7.5
ma
turkeyben
turkey-be-n
7.5
be
6.6 Linguistic Interpretation
Automated Insight:
The language Central Kanuri shows high morphological productivity. The subword models are significantly more efficient than word models, suggesting a rich system of affixation or compounding.
Note on Idiomaticity: The high Idiomaticity Gap suggests a large number of frequent multi-word expressions or formulaic sequences that are statistically distinct from their component parts.
7. Summary & Recommendations
Performance Dashboard
Production Recommendations
Component
Recommended
Rationale
Tokenizer
64k BPE
Best compression (4.58x)
N-gram
2-gram
Lowest perplexity (249)
Markov
Context-4
Highest predictability (97.6%)
Embeddings
100d
Balanced semantic capture and isotropy
Appendix: Metrics Glossary & Interpretation Guide
This section provides definitions, intuitions, and guidance for interpreting the metrics used throughout this report.
Tokenizer Metrics
Compression Ratio
Definition: The ratio of characters to tokens (chars/token). Measures how efficiently the tokenizer represents text.
Intuition: Higher compression means fewer tokens needed to represent the same text, reducing sequence lengths for downstream models. A 3x compression means ~3 characters per token on average.
What to seek: Higher is generally better for efficiency, but extremely high compression may indicate overly aggressive merging that loses morphological information.
Average Token Length (Fertility)
Definition: Mean number of characters per token produced by the tokenizer.
Intuition: Reflects the granularity of tokenization. Longer tokens capture more context but may struggle with rare words; shorter tokens are more flexible but increase sequence length.
What to seek: Balance between 2-5 characters for most languages. Arabic/morphologically-rich languages may benefit from slightly longer tokens.
Unknown Token Rate (OOV Rate)
Definition: Percentage of tokens that map to the unknown/UNK token, indicating words the tokenizer cannot represent.
Intuition: Lower OOV means better vocabulary coverage. High OOV indicates the tokenizer encounters many unseen character sequences.
What to seek: Below 1% is excellent; below 5% is acceptable. BPE tokenizers typically achieve very low OOV due to subword fallback.
N-gram Model Metrics
Perplexity
Definition: Measures how "surprised" the model is by test data. Mathematically: 2^(cross-entropy). Lower values indicate better prediction.
Intuition: If perplexity is 100, the model is as uncertain as if choosing uniformly among 100 options at each step. A perplexity of 10 means effectively choosing among 10 equally likely options.
What to seek: Lower is better. Perplexity decreases with larger n-grams (more context). Values vary widely by language and corpus size.
Entropy
Definition: Average information content (in bits) needed to encode the next token given the context. Related to perplexity: perplexity = 2^entropy.
Intuition: High entropy means high uncertainty/randomness; low entropy means predictable patterns. Natural language typically has entropy between 1-4 bits per character.
What to seek: Lower entropy indicates more predictable text patterns. Entropy should decrease as n-gram size increases.
Coverage (Top-K)
Definition: Percentage of corpus occurrences explained by the top K most frequent n-grams.
Intuition: High coverage with few patterns indicates repetitive/formulaic text; low coverage suggests diverse vocabulary usage.
What to seek: Depends on use case. For language modeling, moderate coverage (40-60% with top-1000) is typical for natural text.
Markov Chain Metrics
Average Entropy
Definition: Mean entropy across all contexts, measuring average uncertainty in next-word prediction.
Intuition: Lower entropy means the model is more confident about what comes next. Context-1 has high entropy (many possible next words); Context-4 has low entropy (few likely continuations).
What to seek: Decreasing entropy with larger context sizes. Very low entropy (<0.1) indicates highly deterministic transitions.
Branching Factor
Definition: Average number of unique next tokens observed for each context.
Intuition: High branching = many possible continuations (flexible but uncertain); low branching = few options (predictable but potentially repetitive).
What to seek: Branching factor should decrease with context size. Values near 1.0 indicate nearly deterministic chains.
Predictability
Definition: Derived metric: (1 - normalized_entropy) × 100%. Indicates how deterministic the model's predictions are.
Intuition: 100% predictability means the next word is always certain; 0% means completely random. Real text falls between these extremes.
What to seek: Higher predictability for text generation quality, but too high (>98%) may produce repetitive output.
Vocabulary & Zipf's Law Metrics
Zipf's Coefficient
Definition: The slope of the log-log plot of word frequency vs. rank. Zipf's law predicts this should be approximately -1.
Intuition: A coefficient near -1 indicates the corpus follows natural language patterns where a few words are very common and most words are rare.
What to seek: Values between -0.8 and -1.2 indicate healthy natural language distribution. Deviations may suggest domain-specific or artificial text.
R² (Coefficient of Determination)
Definition: Measures how well the linear fit explains the frequency-rank relationship. Ranges from 0 to 1.
Intuition: R² near 1.0 means the data closely follows Zipf's law; lower values indicate deviation from expected word frequency patterns.
What to seek: R² > 0.95 is excellent; > 0.99 indicates near-perfect Zipf adherence typical of large natural corpora.
Vocabulary Coverage
Definition: Cumulative percentage of corpus tokens accounted for by the top N words.
Intuition: Shows how concentrated word usage is. If top-100 words cover 50% of text, the corpus relies heavily on common words.
What to seek: Top-100 covering 30-50% is typical. Higher coverage indicates more repetitive text; lower suggests richer vocabulary.
Word Embedding Metrics
Isotropy
Definition: Measures how uniformly distributed vectors are in the embedding space. Computed as the ratio of minimum to maximum singular values.
Intuition: High isotropy (near 1.0) means vectors spread evenly in all directions; low isotropy means vectors cluster in certain directions, reducing expressiveness.
What to seek: Higher isotropy generally indicates better-quality embeddings. Values > 0.1 are reasonable; > 0.3 is good. Lower-dimensional embeddings tend to have higher isotropy.
Average Norm
Definition: Mean magnitude (L2 norm) of word vectors in the embedding space.
Intuition: Indicates the typical "length" of vectors. Consistent norms suggest stable training; high variance may indicate some words are undertrained.
What to seek: Relatively consistent norms across models. The absolute value matters less than consistency (low std deviation).
Cosine Similarity
Definition: Measures angular similarity between vectors, ranging from -1 (opposite) to 1 (identical direction).
Intuition: Words with similar meanings should have high cosine similarity. This is the standard metric for semantic relatedness in embeddings.
What to seek: Semantically related words should score > 0.5; unrelated words should be near 0. Synonyms often score > 0.7.
t-SNE Visualization
Definition: t-Distributed Stochastic Neighbor Embedding - a dimensionality reduction technique that preserves local structure for visualization.
Intuition: Clusters in t-SNE plots indicate groups of semantically related words. Spread indicates vocabulary diversity; tight clusters suggest semantic coherence.
What to seek: Meaningful clusters (e.g., numbers together, verbs together). Avoid over-interpreting distances - t-SNE preserves local, not global, structure.
General Interpretation Guidelines
Compare within model families: Metrics are most meaningful when comparing models of the same type (e.g., 8k vs 64k tokenizer).
Consider trade-offs: Better performance on one metric often comes at the cost of another (e.g., compression vs. OOV rate).
Context matters: Optimal values depend on downstream tasks. Text generation may prioritize different metrics than classification.
Corpus influence: All metrics are influenced by corpus characteristics. Wikipedia text differs from social media or literature.
Language-specific patterns: Morphologically rich languages (like Arabic) may show different optimal ranges than analytic languages.
Visualizations Index
Visualization
Description
Tokenizer Compression
Compression ratios by vocabulary size
Tokenizer Fertility
Average token length by vocabulary
Tokenizer OOV
Unknown token rates
Tokenizer Total Tokens
Total tokens by vocabulary
N-gram Perplexity
Perplexity by n-gram size
N-gram Entropy
Entropy by n-gram size
N-gram Coverage
Top pattern coverage
N-gram Unique
Unique n-gram counts
Markov Entropy
Entropy by context size
Markov Branching
Branching factor by context
Markov Contexts
Unique context counts
Zipf's Law
Frequency-rank distribution with fit
Vocab Frequency
Word frequency distribution
Top 20 Words
Most frequent words
Vocab Coverage
Cumulative coverage curve
Embedding Isotropy
Vector space uniformity
Embedding Norms
Vector magnitude distribution
Embedding Similarity
Word similarity heatmap
Nearest Neighbors
Similar words for key terms
t-SNE Words
2D word embedding visualization
t-SNE Sentences
2D sentence embedding visualization
Position Encoding
Encoding method comparison
Model Sizes
Storage requirements
Performance Dashboard
Comprehensive performance overview
About This Project
Data Source
Models trained on wikipedia-monthly - a monthly snapshot of Wikipedia articles across 300+ languages.
Project
A project by Wikilangs - Open-source NLP models for every Wikipedia language.