Comprehensive Research Report & Full Ablation Study
This repository contains NLP models trained and evaluated by Wikilangs, specifically on Malayalam 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)
Entropy Trend: Decreases with larger n-grams (more predictable)
Coverage: Top-1000 patterns cover ~8% 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
0.6805
1.603
5.82
2,337,199
31.9%
1
Subword
0.9605
1.946
14.48
34,171
3.9%
2
Word
0.1758
1.130
1.40
13,589,609
82.4%
2
Subword
0.7010
1.626
5.25
494,724
29.9%
3
Word
0.0434
1.031
1.07
18,962,615
95.7%
3
Subword
0.5422
1.456
3.38
2,596,737
45.8%
4
Word
0.0148 🏆
1.010
1.02
20,273,957
98.5%
4
Subword
0.4401
1.357
2.35
8,776,422
56.0%
Generated Text Samples (Word-based)
Below are text samples generated from each word-based Markov chain model:
Context Size 1:
ഒരു ദുരന്തനാടകമായ മാക്ബെത്തിലെ ലേഡി ബേർഡ് എന്നിവയെ ലയിപ്പിച്ച് ജിയോസ്റ്റാർ ഇന്ത്യ കോസ്റ്റാറിക്ക യു ഡ...
ഈ പ്രദേശത്തിന്റെ സാമൂഹിക സമത്വം എന്ന നിലയിലാണ് പ്രശസ്തൻ ജൊനാഥൻ വാൻ ഐക്കിന്റെ ചിത്രമാണ് sify archived...
എന്ന ഗാനത്തിന് ഹിന്ദി ടെലിവിഷനിലും അഭിനയം കൂടാതെ ഭസ്മലേപനം തപോവേഷം യോഗ്യമല്ലാത്ത വിഭവങ്ങൾ ഉപയോഗിക്കു...
Context Size 2:
of the vietnam war protests vietnam war in history set for tuesday observer reporter retrieved decem...
പുറത്തേക്കുള്ള കണ്ണികൾ സർവ്വകലാശാലക്കു കീഴിലുള്ള കലാലയങ്ങൾ പുറേത്തേക്കുള്ള കണ്ണികൾ ഗവൺെമെന്റ് കാേളേജ...
അവലംബം പുറത്തേക്കുള്ള കണ്ണികൾ bananas org മുസെല്ല ലാസിയോകാർപമ്യൂസെല്ല ലാസിയോകാർപ മരങ്ങൾ സസ്യങ്ങൾ ബംഗ...
Context Size 3:
അവലംബം പുറത്തേക്കുള്ള കണ്ണികൾ strasbourg the most european french city official french website in en...
അവലംബം പുറം കണ്ണികൾ അമേരിക്കയിലെ സസ്യജാലം സസ്യജാലം സസ്യജാലം സസ്യജാലം സസ്യജാലം അധിനിവേശസസ്യങ്ങൾ
കെ ജെ യേശുദാസ് കൈതപ്രം ദാമോദരൻ നമ്പൂതിരി തങ്കനിലാ കെ എസ് ചിത്ര അണിയറ പ്രവർത്തകർ ഛായാഗ്രഹണം ആനന്ദക്കു...
Context Size 4:
സി പി ഐ എം ആക്കാവിള സതീക്ക് എൻ ഡി എ എം കെ രാഘവൻ കോൺഗ്രസ് ഐ യു ഡി എഫ് ഫിലിപ്പോസ് തോമസ്
കൺസർവേറ്റീവ് കൺസർവേറ്റീവ് കൺസർവേറ്റീവ് കൺസർവേറ്റീവ് ലേബർhull south west ലിബറൽ ലിബറൽ ലിബറൽ ലിബറൽ ലിബറ...
കേരള സാഹിത്യ അക്കാദമി പുരസ്കാരം ഈ കൃതിക്ക് ലഭിച്ചിട്ടുണ്ട് ഈ പുസ്തകത്തിൽ നോവലിന്റെയോ കഥപറച്ചിലിന്റെയ...
Generated Text Samples (Subword-based)
Below are text samples generated from each subword-based Markov chain model:
Context Size 1:
_234_ഭാവരിൽ_കളജില്ല._
._കുറൽ_._നാപുറൻസിന്റായിക്കു
കൾഡ്_ചലയുള്ളയ്ക്ക്_ഗുണങ്ങളെ_ൽ
Context Size 2:
._തരണത്തിലേർപ്പെട്ടില്ല._അക്കിലിനു
ൽ_ബസിയിൽ_നിക്കോളാസ്_പ്രകൃതിയുടെ
_അവനോടെ_പൗരന്മാർ_മന്നേയൻ_റി
Context Size 3:
ന്നു._അതിർത്തിയോ_കൃഷ്ണൻ_:_♂).
_അവതരിപ്പിക്കുന്നതുവരെ_പോരാട്ടത്തിനു_
കൾ_ഡാർട്ട്_ഗാലറി_ഡൈക്ലോഫെനാക്_ഉ
Context Size 4:
_ഒരു_മെമ്മറിയും_താലൂക്കുകൾ,_മകൾ
രുന്നു._ചൈനീസ്_ലിപി:_মোহাম্মদ_সাহা
_എന്ന_പട്ടണം._ഒന്നാം_ലോകമഹായുദ്ധസ
Key Findings
Best Predictability: Context-4 (word) with 98.5% predictability
Branching Factor: Decreases with context size (more deterministic)
Memory Trade-off: Larger contexts require more storage (8,776,422 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
801,863
Total Tokens
20,480,775
Mean Frequency
25.54
Median Frequency
3
Frequency Std Dev
511.27
Most Common Words
Rank
Word
Frequency
1
ഒരു
243,510
2
ഈ
162,409
3
എന്ന
110,774
4
the
94,058
5
of
88,580
6
അവലംബം
64,447
7
ഇത്
55,817
8
നിന്ന്
50,269
9
അദ്ദേഹം
49,641
10
and
49,492
Least Common Words (from vocabulary)
Rank
Word
Frequency
1
areekode
2
2
ഭാഗമാകുവാനും
2
3
ഗായകനെയും
2
4
ഗഫൂറിനെ
2
5
സ്കൂളിനായി
2
6
തെല്ലിപ്പളൈ
2
7
എരവല്ലൻ
2
8
കൈകാടി
2
9
പട്ടപ്പു
2
10
ടെനോം
2
Zipf's Law Analysis
Metric
Value
Zipf Coefficient
0.8771
R² (Goodness of Fit)
0.995192
Adherence Quality
excellent
Coverage Analysis
Top N Words
Coverage
Top 100
14.6%
Top 1,000
34.1%
Top 5,000
52.2%
Top 10,000
60.6%
Key Findings
Zipf Compliance: R²=0.9952 indicates excellent adherence to Zipf's law
High Frequency Dominance: Top 100 words cover 14.6% of corpus
Long Tail: 791,863 words needed for remaining 39.4% 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
0.7956
0.3438
N/A
N/A
mono_64d
64
0.7180
0.2843
N/A
N/A
mono_128d
128
0.6063
0.2328
N/A
N/A
aligned_32d
32
0.7956 🏆
0.3488
0.0920
0.4000
aligned_64d
64
0.7180
0.2864
0.1940
0.5680
aligned_128d
128
0.6063
0.2384
0.2720
0.6480
Key Findings
Best Isotropy: aligned_32d with 0.7956 (more uniform distribution)
Semantic Density: Average pairwise similarity of 0.2891. Lower values indicate better semantic separation.
Alignment Quality: Aligned models achieve up to 27.2% 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
-0.114
Low formulaic 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.
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
atio
3.14x
71 contexts
ratio, jatio, ratios
tion
3.05x
76 contexts
tiong, action, nation
ment
3.00x
81 contexts
ament, mentz, mentv
nter
2.90x
79 contexts
inter, unter, enter
stor
3.04x
62 contexts
storm, stora, stork
isto
3.32x
40 contexts
histo, cristo, aristo
ture
2.88x
57 contexts
turek, future, suture
mber
2.89x
56 contexts
ember, amber, imber
nati
3.23x
36 contexts
nation, donati, naties
ctio
3.04x
39 contexts
action, sectio, lectio
iver
2.86x
48 contexts
river, liver, siver
ersi
2.82x
44 contexts
persia, mersin, bersih
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
-ക
-ൽ
76 words
കാരണത്താൽ, കോട്ടമുറിക്കൽ
-പ
-ൽ
58 words
പാരവശ്യത്തിൽ, പ്രഫഷനൽ
-അ
-ൽ
36 words
അഞ്ചൽ, അക്ബർനാമയിൽ
-ക
-ൾ
33 words
കാസ്റ്റിംഗുകൾ, കുടുംബവഴക്കുകൾ
-ക
-ൻ
33 words
കാളിയൻ, കോടീശ്വരൻ
-പ
-യ
33 words
പ്രായ, പ്രോഗ്രാമായ
-സ
-ൽ
32 words
സൈപ്രസ്സിൽ, സെപ്റ്റംബരിൽ
-ക
-ള
32 words
ക്ഷേത്രകടവിലുള്ള, കാഴ്ചപ്പാടിലുള്ള
-വ
-ൽ
31 words
വിധേയരാകുന്നതിൽ, വെൽഡനാഗ്രത്തിൽ
-വ
-ള
28 words
വംശങ്ങളോടുള്ള, വഞ്ചിമുട്ടംപിള്ള
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
theophilus
theophil-us
4.5
theophil
ഉന്നതപദവികൾ
ഉന്നതപദവി-കൾ
4.5
ഉന്നതപദവി
മലയാളലിപികൾ
മലയാളലിപി-കൾ
4.5
മലയാളലിപി
നക്ഷത്രമാണിത്
ന-ക-്ഷത്രമാണിത്
4.5
്ഷത്രമാണിത്
ഡക്കാന്റെ
ഡ-ക-്കാന്റെ
4.5
്കാന്റെ
അമരക്കാരും
അ-മരക്കാരും
4.5
മരക്കാരും
അറസ്റ്റിൽ
അ-റസ്റ്റിൽ
4.5
റസ്റ്റിൽ
അശ്രദ്ധയും
അ-ശ്രദ്ധയും
4.5
ശ്രദ്ധയും
നിംബാർക്കൻ
നിംബാർക്ക-ൻ
4.5
നിംബാർക്ക
michigans
michigan-s
4.5
michigan
schimperi
schimper-i
4.5
schimper
പാടിത്തുടങ്ങിയ
പാടിത്തുടങ്ങി-യ
4.5
പാടിത്തുടങ്ങി
orientales
oriental-es
4.5
oriental
കൊത്തുപണികൾ
കൊത്തുപണി-കൾ
4.5
കൊത്തുപണി
ശബ്ദംകേട്ട്
ശ-ബ-്ദംകേട്ട്
3.0
്ദംകേട്ട്
6.6 Linguistic Interpretation
Automated Insight:
The language Malayalam shows high morphological productivity. The subword models are significantly more efficient than word models, suggesting a rich system of affixation or compounding.
7. Summary & Recommendations
Performance Dashboard
Production Recommendations
Component
Recommended
Rationale
Tokenizer
64k BPE
Best compression (5.37x)
N-gram
2-gram
Lowest perplexity (4,333)
Markov
Context-4
Highest predictability (98.5%)
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.
