🏥 VitalLM-50M-Instruct: Instruction-Tuned Medical SLM

A 50.55 million parameter Small Language Model (SLM) fine-tuned for instruction-following clinical dialogue — combining deep biomedical pretraining with supervised instruction alignment.

VitalLM-50M-Instruct is the instruction-tuned successor to VitalLM-50M. Built on a custom decoder-only Transformer architecture pretrained on 764M+ biomedical tokens, this model has been further refined via Supervised Fine-Tuning (SFT) on a curated medical instruction dataset — enabling it to follow clinical prompts, answer patient queries, and generate structured medical responses.

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🚀 Key Architectural Choices

1. SwiGLU Activation Function

Unlike standard GPT models that use ReLU or GeLU, VitalLM-50M utilizes SwiGLU to increase reasoning density — enabling more nuanced capture of complex, non-linear relationships found in medical symptoms and drug interactions.

2. Specialized Biomedical Tokenization

A custom ByteLevelBPE Tokenizer with a 16,384 vocabulary size was developed to preserve medical terminology as meaningful units (e.g., preventing fragmentation of terms like bronchitis or tachycardia), significantly improving inference accuracy and speed.

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📊 Technical Specifications

Parameter	Value	Notes
Total Parameters	50.55 Million	Optimized for edge/mobile deployment
Architecture	Decoder-only Transformer	Custom GPT-style
Layers (n_layer)	10	Hierarchical clinical reasoning
Attention Heads (n_head)	8	Multi-head attention
Embedding Dim (n_embd)	512	Medical concept vector space
Context Window	256 tokens	Clinical dialogues & Q&A
Activation	SwiGLU	Enhanced reasoning density
Tokenizer	ByteLevelBPE	Vocabulary size: 16,384

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📈 Training — Stage 1: Pretraining

Data Strategy

• Corpus: 550M+ tokens of filtered biomedical research, clinical guidelines, and synthetic medical dialogues.
• Sources: PubMed QA, MedMCQA, BI55/MedText.
• Pre-processing: Extensive de-duplication and signal-preserving cleaning.

Hardware & Optimization

• Compute: NVIDIA P100 GPU (Kaggle)
• Optimizer: AdamW with Weight Decay (0.1)
• Scheduler: Cosine Learning Rate Decay
• Strategy: Multi-session training with custom state-recovery logic

Pretraining Results

Metric	Value
Final Training Loss	3.32
Final Validation Loss	3.66
Generalization Gap	0.34

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🎯 Training — Stage 2: Supervised Fine-Tuning (SFT)

SFT Dataset

• Dataset: Mohammed-Altaf/medical-instruction-100k
• Size: ~100,000 instruction-response pairs
• Format: Instruction-following medical Q&A covering symptoms, diagnoses, treatments, and clinical dialogue

SFT Objective

The model was fine-tuned to shift from open-ended generation (pretraining) to structured instruction-following — enabling it to respond reliably to clinical prompts in a doctor-patient dialogue format.

SFT Hardware & Optimization

• Compute: NVIDIA P100 GPU (Kaggle)
• Optimizer: AdamW with Weight Decay (0.1)
• Scheduler: Cosine Learning Rate Decay with linear warmup (peak LR: 2e-5)
• Training Duration: ~4,300 iterations

SFT Results

Metric	Value
Best Training Loss	2.9866
Final Training Loss	~2.96
Final Validation Loss	~2.99
Final Train Perplexity	~19.5
Final Val Perplexity	~19.8

🛠 Usage & Implementation

Download Required Files

Before running any code, you need the following files. Download them directly from this repository and the Hugging Face model page:

File	Source	Description
model.py	GitHub	Custom model architecture
vocab_50m.json	Hugging Face	Tokenizer vocabulary
merges_50m.txt	Hugging Face	BPE merge rules

⚠️ All files must be present in the same working directory before running inference. model.py contains the custom SLM and SLMConfig classes which are not available in the standard transformers library and cannot be skipped.

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Install Dependencies

pip install torch transformers tokenizers safetensors

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Loading the Instruction-Tuned Model

import torch
import torch.nn.functional as F
from model import SLM, SLMConfig
from tokenizers import ByteLevelBPETokenizer
from transformers import PreTrainedTokenizerFast
from safetensors.torch import load_file
from huggingface_hub import hf_hub_download

device = "cuda" if torch.cuda.is_available() else "cpu"

# Download safetensors weights
weights_path = hf_hub_download(
    repo_id="aman0419/Vitallm-50M-Instruct",
    filename="model.safetensors" # use vital_lm_50m_weights.safetensors for pretrained model
)

# Initialize model
config = SLMConfig(vocab_size=16384, n_layer=10, n_head=8, n_embd=512, block_size=256, dropout=0.0)
model = SLM(config)

# Load safetensors and fix weight tying
state_dict = load_file(weights_path)
if 'lm_head.weight' in state_dict and 'transformer.wte.weight' not in state_dict:
    state_dict['transformer.wte.weight'] = state_dict['lm_head.weight']

model.load_state_dict(state_dict)
model.to(device)
model.eval()

# Load tokenizer
base_tokenizer = ByteLevelBPETokenizer(vocab="vocab_50m.json", merges="merges_50m.txt")
tokenizer = PreTrainedTokenizerFast(
    tokenizer_object=base_tokenizer,
    eos_token="<|endoftext|>",
    bos_token="<|endoftext|>",
    unk_token="<|endoftext|>",
    pad_token="<|endoftext|>"
)

Generation Function

def generate(prompt, max_new_tokens=130, temperature=0.25, top_k=30, top_p=0.9, repetition_penalty=1.25):
    input_ids = torch.tensor(tokenizer.encode(prompt), dtype=torch.long).unsqueeze(0).to(device)
    
    with torch.no_grad():
        for _ in range(max_new_tokens):
            input_ids_cond = input_ids[:, -256:]
            logits, _ = model(input_ids_cond)
            logits = logits[:, -1, :] / temperature

            for token in set(input_ids[0].tolist()):
                if logits[0, token] > 0:
                    logits[0, token] /= repetition_penalty
                else:
                    logits[0, token] *= repetition_penalty

            sorted_logits, sorted_indices = torch.sort(logits, descending=True)
            cumulative_probs = torch.cumsum(F.softmax(sorted_logits, dim=-1), dim=-1)
            sorted_indices_to_remove = cumulative_probs > top_p
            sorted_indices_to_remove[..., 1:] = sorted_indices_to_remove[..., :-1].clone()
            sorted_indices_to_remove[..., 0] = 0
            logits[0, sorted_indices[sorted_indices_to_remove]] = -float('Inf')

            if top_k is not None:
                v, _ = torch.topk(logits, min(top_k, logits.size(-1)))
                logits[logits < v[:, [-1]]] = -float('Inf')

            next_token = torch.multinomial(F.softmax(logits, dim=-1), num_samples=1)
            input_ids = torch.cat((input_ids, next_token), dim=1)

            if next_token.item() == tokenizer.eos_token_id:
                break

    return tokenizer.decode(input_ids[0].tolist(), skip_special_tokens=True)

# Test
if __name__ == "__main__":
    prompt = "Patient: I have been feeling very thirsty and urinating frequently. Doctor:"
    response = generate(prompt)
    print(f"Response: {response}")

Recommended Prompt Format

For best results with the SFT model, use the following dialogue-style format:

Patient: <symptom/question description>
Doctor:

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⚠️ Limitations & Ethical Considerations

• Not a clinical tool: VitalLM-50M-Instruct is a research model and is not validated for real-world medical use. Outputs must not be used as a substitute for professional medical advice.
• Hallucination risk: As with all language models, this model may generate plausible-sounding but factually incorrect medical information.
• Context length: The 256-token context window limits complex multi-turn reasoning.
• Scope: The model performs best on common conditions and standard clinical language; rare diseases and specialized sub-fields may yield lower quality outputs.

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