Raising Bars, Not Parameters: LilMoo Compact Language Model for Hindi
Authors: Shiza Fatimah, Aniket Sen, Sophia Falk, Florian Mai, Lucie Flek, Nicholas Kluge Corrêa
Organizations: Bonn-Aachen International Center for Information Technology (b-it) / CAISA Lab · Lamarr Institute for Machine Learning and Artificial Intelligence · Helmholtz-Institut für Strahlen- und Kernphysik · Bonn Sustainable AI Lab
The dominance of large multilingual foundation models has widened linguistic inequalities in Natural Language Processing (NLP), often leaving low-resource languages underrepresented. This paper introduces LilMoo, a 0.6-billion-parameter Hindi language model trained entirely from scratch to address this gap. Unlike prior Hindi models that rely on continual pretraining from opaque multilingual foundations, LilMoo is developed through a fully transparent and reproducible pipeline optimized for limited compute environments. We construct a high-quality Hindi corpus (GigaLekh) filtered through both heuristic and learned (LLM-as-a-judge) methods, complemented by bilingual augmentation with curated English data. Using this dataset, we explore various training recipes for small-scale language models. Across comprehensive evaluation suites, LilMoo consistently outperforms comparably sized multilingual baselines such as Qwen2.5-0.5B and Qwen3-0.6B, demonstrating that well-designed language-specific pretraining can rival large multilingual models at the sub-billion-parameter range.
Figures & tables
Subset
Documents
Size
Tokens
default
83,081,507
260.68 GB
90,705,245,239
excluded
498,892
1.76 GB
1,545,290,236
Total
83,580,399
262.44 GB
92,250,535,475
Table 1: Statistics for subsets.
Tokenizer
Tokens (31500 words)
Vocab Size
Fertility
PCW
UNK
LilMoo
46129
49152
1.46
0.50
0
HindRoBERTa
50697
250002
1.61
0.31
0
Nemotron-Hindi-4B
52111
256000
1.65
0.30
0
IndicBERT
54213
200000
1.72
0.40
2
Gemma-2-2b
54379
256000
1.73
0.47
0
Llama-3.2
63891
128256
2.02
0.61
0
Table 2: Tokenizer Evaluation Metrics Comparison Across Multiple Tokenizers for Hindi (Ordered by Fertility)
Parameter
Value
Activation
SwiGLU
Hidden d (Residual Stream)
1,536
Feed-forward (MLP)
3,072
Context Length
4,096 tokens
Attention Heads
16
Attention Head d
96
Table 3: Architectural Specifications.
Parameter
Value / Description
Total batch size
2,097,152 tokens
Precision
BF16 with TF32 enabled
Optimizer
AdamW
Maximum learning rate
7e-4
Adam β1,β2
0.9, 0.95
Adam ϵ
1e-8
Table 4: Shared Training Hyperparameters for Both Recipes
Dataset Name
Subset
Size (Tokens)
GigaLekh
50B (Total)
Edu Score of 3
34.95B
Edu Score of 4
14.30B
Edu Score of 5
163.96M
HuggingFaceFW/fineweb-edu
49.29B (Total)
Edu Score of 3
35.00B
Table 5: Summary of Datasets Used in Multi-Stage Recipe
Stage
Hindi% (tokens)
English% (tokens)
Warmup+Stable
48.5 ( ∼ 70B)
51.5 ( ∼ 74B)
Stable
52 ( ∼ 81B)
48 ( ∼ 75B)
Stable+SqrtDecay
53 ( ∼ 44B)
47 ( ∼ 39B)
Table 6: Language Proportions Across Stages in Multi-Stage Recipe
Figure 1: Pretraining loss curve for the LilMoo pair.
Figure 2: Gradient Statistics for the LilMoo pair.
Figure 3: Per-benchmark performance across our evaluation suite (Qwen2.5/3 serve as Baselines).
Figure 4: NPM scores for both LilMoo models and both Qwen baselines.
Model
Aggregate NPM
MILU
CSQA
ARC
MMLU
HellaSwag
PIQA
LilMoo-v0.2
9.94
0.28
0.42
0.29
0.27
0.32
0.58
LilMoo-v0.1
8.70
0.28
0.42
0.25
0.26
0.32
0.58
Qwen3-1.7B
7.80
0.37
0.34
0.26
0.36
0.28
0.50
OpenHathi-7B-Hi-v0.1-Base
7.64
0.30
0.36
0.23
0.27
0.31
0.58
Airavata
6.63
0.28
0.36
0.22
0.27
0.29
0.58
gemma-2-2b-it
6.53
0.36
0.36
0.22
0.31
0.29
0.50
Table 7: Performance comparison against other models, beyond the Qwen2.5/3 baselines.
Model
Total Duration (hours)
GPU-hours
Energy consumed (kWh)
CO 2 emitted (kg CO 2 eq)
Total Compute (FLOPs)
LilMoo-v0.2
∼ 327.50
∼ 2648.7
1346.76
513.05
∼ 1.285e21
LilMoo-v0.1
∼ 346.97
∼ 2797.1
1414.21
538.74
∼ 1.357e21
Table 8: Training Resource Consumption
Figure 5: Performance vs Compute for LilMoo Models vs Qwen Baselines
Appendix figures & tables10 assets
Supplementary material from the paper’s appendix.
Appendix
Source Type
Dataset / Crawl
License(s)
Common Crawl
CC-MAIN-2025-30
ODC-By v1.0, CommonCrawl ToU
CC-MAIN-2025-26
ODC-By v1.0, CommonCrawl ToU
CC-MAIN-2025-05
ODC-By v1.0, CommonCrawl ToU
CC-MAIN-2024-51
ODC-By v1.0, CommonCrawl ToU
CC-MAIN-2023-50
ODC-By v1.0, CommonCrawl ToU
CC-MAIN-2022-49
ODC-By v1.0, CommonCrawl ToU
Appendix
Table B.1: Data sources organized by source type.
Model Name
Task
Precision
Recall
F1 Macro
Accuracy
HindRoBERTa
Educational
0.52
0.47
0.49
0.72
Toxicity
0.59
0.45
0.47
0.70
IndicBERT
Educational
0.51
0.47
0.48
0.71
Toxicity
0.56
0.43
0.44
0.69
Appendix
Table C.2: Evaluation results for educational-quality and toxicity classifiers on the test set using the original 5-class labels.
Dataset Name
Subset
Size (Tokens)
Repetition Factor
GigaLekh
Edu Score of 3
34.9B
2
HuggingFaceFW/fineweb-edu
Edu Score of 3
40.00B
1
HuggingFaceTB/finemath
Edu Score of 4
8.59B
2
allenai/big-reasoning-traces
All
2.44B
2
allenai/math-meta-reasoning-filtered ∗
All
1.24B
2
nvidia/OpenScience
All
9.7B
1
Appendix
Table D.3: Data mixture for Stage-1
Dataset Name
Subset
Size (Tokens)
Repetition Factor
GigaLekh
Edu Score of 3
34.9B
1.5
Edu Score of 4
14.3B
2
HuggingFaceFW/fineweb-edu
Edu Score of 4
14.22B
1
HuggingFaceTB/smollm-corpus
All
29.4B
1
HuggingFaceTB/finemath
Edu Score of 4
8.59B
1
Edu Score of 5
1.08B
2
Appendix
Table D.4: Data mixture for Stage-2
Dataset Name
Subset
Size (Tokens)
Repetition Factor
GigaLekh
Edu Score of 4
14.3B
3
Edu Score of 5
0.16B
5
HuggingFaceFW/fineweb-edu
Edu Score of 5
0.068B
5
HuggingFaceTB/smollm-corpus
All
29.4B
1
HuggingFaceTB/finemath
Edu Score of 5
1.08B
3
allenai/big-reasoning-traces
All
2.44B
2
Appendix
Table D.5: Data mixture for Stage-3
Benchmark
n-shot
Baseline
Metric
ARC
5-shot
25
acc
MMLU
5-shot
25
acc
HellaSwag
5-shot
25
acc
TruthfulQA
0-shot
22.5
mc1
MILU
5-shot
25
acc
CSQA
5-shot
25
acc
Appendix
Table E.6: Summary of Evaluation Benchmarks
Figure E.1: Per-benchmark Performance across training checkpoints.
Figure E.2: NPM aggregated score of all benchmarks.
Benchmark
Baseline
Threshold
First Step
Tokens (B)
Score
%
ARC
0.250
0.300
80000
167.770
0.301
+0.051
HellaSwag
0.250
0.300
5000
10.490
0.311
+0.061
MMLU
0.250
0.300
Not Reached
-
-
-
TruthfulQA MC1
0.225
0.275
Not Reached
-
-
-
COPA
0.500
0.550
10000
20.970
0.559
+0.059
IITP MR
0.330
0.380
5000
10.490
0.387
+0.057
Appendix
Table E.7: Training tokens required for v0.1 to surpass random baselines by 5%.
Figure E.3: Noise analysis for the 10 benchmarks in our Hindi evaluation suite.
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