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Walkthrough – Token Compression MVP Review & Enhancement

Summary

Performed a rigorous review of the full 20-file codebase, fixed 4 bugs, added a compression visualization feature, and created 2 comprehensive documentation files.


Phase 1: Bug Fixes

Bug 1 – config.py: Fragile type resolution in _dict_to_dataclass

Problem: Used globals() to resolve string type annotations, which fails when annotations aren't importable from the module scope.

Fix: Replaced with an explicit _DATACLASS_REGISTRY dict mapping field names to their concrete dataclass types.

"""Central configuration for the prompt-optimizer project."""

from __future__ import annotations

import logging
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Optional

import yaml

logger = logging.getLogger(__name__)

# ---------------------------------------------------------------------------
# Project root – resolved relative to this file so it works both locally
# and on Colab after cloning the repo.
# ---------------------------------------------------------------------------
PROJECT_ROOT = Path(__file__).resolve().parent.parent


@dataclass
class ModelConfig:
    name: str = "mistralai/Mistral-7B-Instruct-v0.2"
    trust_remote_code: bool = True
    torch_dtype: str = "float16"  # "float16" | "bfloat16" | "auto"


@dataclass
class QuantizationConfig:
    load_in_4bit: bool = True
    bnb_4bit_quant_type: str = "nf4"
    bnb_4bit_compute_dtype: str = "float16"
    bnb_4bit_use_double_quant: bool = True


@dataclass
class LoraConfig:
    r: int = 16
    lora_alpha: int = 32
    lora_dropout: float = 0.05
    target_modules: list[str] = field(
        default_factory=lambda: ["q_proj", "k_proj", "v_proj", "o_proj"]
    )
    bias: str = "none"
    task_type: str = "CAUSAL_LM"


@dataclass
class TrainingConfig:
    output_dir: str = "outputs/checkpoints"
    num_train_epochs: int = 3
    per_device_train_batch_size: int = 2
    gradient_accumulation_steps: int = 4
    learning_rate: float = 2e-4
    weight_decay: float = 0.01
    warmup_ratio: float = 0.03
    lr_scheduler_type: str = "cosine"
    max_seq_length: int = 1024
    logging_steps: int = 10
    save_strategy: str = "epoch"
    save_total_limit: int = 2
    fp16: bool = True
    bf16: bool = False
    gradient_checkpointing: bool = True
    optim: str = "paged_adamw_8bit"
    report_to: str = "none"
    seed: int = 42


@dataclass
class GenerationConfig:
    max_new_tokens: int = 512
    temperature: float = 0.3
    top_p: float = 0.9
    repetition_penalty: float = 1.15
    do_sample: bool = True


@dataclass
class DatasetConfig:
    raw_dir: str = "data/raw"
    processed_dir: str = "data/processed"
    train_file: str = "train.jsonl"
    val_file: str = "val.jsonl"
    val_split: float = 0.1
    seed: int = 42
    max_samples: Optional[int] = None  # limit for quick tests


@dataclass
class EvalConfig:
    max_token_threshold: int = 300
    min_compression_ratio: float = 0.5


@dataclass
class UIConfig:
    server_name: str = "0.0.0.0"
    server_port: int = 7860
    share: bool = False


@dataclass
class Config:
    model: ModelConfig = field(default_factory=ModelConfig)
    quantization: QuantizationConfig = field(default_factory=QuantizationConfig)
    lora: LoraConfig = field(default_factory=LoraConfig)
    training: TrainingConfig = field(default_factory=TrainingConfig)
    generation: GenerationConfig = field(default_factory=GenerationConfig)
    dataset: DatasetConfig = field(default_factory=DatasetConfig)
    evaluation: EvalConfig = field(default_factory=EvalConfig)
    ui: UIConfig = field(default_factory=UIConfig)

    # ---- adapter / output helpers ------------------------------------------
    @property
    def adapter_dir(self) -> Path:
        return PROJECT_ROOT / "outputs" / "adapter"

    @property
    def merged_dir(self) -> Path:
        return PROJECT_ROOT / "outputs" / "merged"


# ---------------------------------------------------------------------------
# YAML loader
# ---------------------------------------------------------------------------

def _merge(base: dict, override: dict) -> dict:
    """Recursively merge *override* into *base*."""
    for k, v in override.items():
        if isinstance(v, dict) and isinstance(base.get(k), dict):
            _merge(base[k], v)
        else:
            base[k] = v
    return base


def _dict_to_dataclass(dc_cls: type, data: dict) -> Any:
    """Instantiate a nested dataclass hierarchy from a plain dict."""
    field_types = {f.name: f.type for f in dc_cls.__dataclass_fields__.values()}
    kwargs: dict[str, Any] = {}
    for key, value in data.items():
        if key in field_types and isinstance(value, dict):
            inner_cls = dc_cls.__dataclass_fields__[key].type
            # Resolve string type annotations
            if isinstance(inner_cls, str):
                inner_cls = globals().get(inner_cls, inner_cls)
            kwargs[key] = _dict_to_dataclass(inner_cls, value)
        else:
            kwargs[key] = value
    return dc_cls(**kwargs)


def load_config(yaml_path: Optional[str | Path] = None) -> Config:
    """Load configuration from a YAML file, falling back to defaults."""
    if yaml_path is None:
        yaml_path = PROJECT_ROOT / "configs" / "default.yaml"
    path = Path(yaml_path)
    if path.exists():
        logger.info("Loading config from %s", path)
        with open(path, "r", encoding="utf-8") as fh:
            overrides = yaml.safe_load(fh) or {}
        # Build default dict, merge overrides, convert back
        import dataclasses

        base = dataclasses.asdict(Config())
        merged = _merge(base, overrides)
        return _dict_to_dataclass(Config, merged)
    logger.info("No config file found at %s – using defaults.", path)
    return Config()
===
"""Central configuration for the prompt-optimizer project."""

from __future__ import annotations

import logging
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Optional

import yaml

logger = logging.getLogger(__name__)

# ---------------------------------------------------------------------------
# Project root – resolved relative to this file so it works both locally
# and on Colab after cloning the repo.
# ---------------------------------------------------------------------------
PROJECT_ROOT = Path(__file__).resolve().parent.parent


@dataclass
class ModelConfig:
    name: str = "mistralai/Mistral-7B-Instruct-v0.2"
    trust_remote_code: bool = True
    torch_dtype: str = "float16"  # "float16" | "bfloat16" | "auto"


@dataclass
class QuantizationConfig:
    load_in_4bit: bool = True
    bnb_4bit_quant_type: str = "nf4"
    bnb_4bit_compute_dtype: str = "float16"
    bnb_4bit_use_double_quant: bool = True


@dataclass
class LoraConfig:
    r: int = 16
    lora_alpha: int = 32
    lora_dropout: float = 0.05
    target_modules: list[str] = field(
        default_factory=lambda: ["q_proj", "k_proj", "v_proj", "o_proj"]
    )
    bias: str = "none"
    task_type: str = "CAUSAL_LM"


@dataclass
class TrainingConfig:
    output_dir: str = "outputs/checkpoints"
    num_train_epochs: int = 3
    per_device_train_batch_size: int = 2
    gradient_accumulation_steps: int = 4
    learning_rate: float = 2e-4
    weight_decay: float = 0.01
    warmup_ratio: float = 0.03
    lr_scheduler_type: str = "cosine"
    max_seq_length: int = 1024
    logging_steps: int = 10
    save_strategy: str = "epoch"
    save_total_limit: int = 2
    fp16: bool = True
    bf16: bool = False
    gradient_checkpointing: bool = True
    optim: str = "paged_adamw_8bit"
    report_to: str = "none"
    seed: int = 42


@dataclass
class GenerationConfig:
    max_new_tokens: int = 512
    temperature: float = 0.3
    top_p: float = 0.9
    repetition_penalty: float = 1.15
    do_sample: bool = True


@dataclass
class DatasetConfig:
    raw_dir: str = "data/raw"
    processed_dir: str = "data/processed"
    train_file: str = "train.jsonl"
    val_file: str = "val.jsonl"
    val_split: float = 0.1
    seed: int = 42
    max_samples: Optional[int] = None  # limit for quick tests


@dataclass
class EvalConfig:
    max_token_threshold: int = 300
    min_compression_ratio: float = 0.5


@dataclass
class UIConfig:
    server_name: str = "0.0.0.0"
    server_port: int = 7860
    share: bool = False


@dataclass
class Config:
    model: ModelConfig = field(default_factory=ModelConfig)
    quantization: QuantizationConfig = field(default_factory=QuantizationConfig)
    lora: LoraConfig = field(default_factory=LoraConfig)
    training: TrainingConfig = field(default_factory=TrainingConfig)
    generation: GenerationConfig = field(default_factory=GenerationConfig)
    dataset: DatasetConfig = field(default_factory=DatasetConfig)
    evaluation: EvalConfig = field(default_factory=EvalConfig)
    ui: UIConfig = field(default_factory=UIConfig)

    # ---- adapter / output helpers ------------------------------------------
    @property
    def adapter_dir(self) -> Path:
        return PROJECT_ROOT / "outputs" / "adapter"

    @property
    def merged_dir(self) -> Path:
        return PROJECT_ROOT / "outputs" / "merged"


# ---------------------------------------------------------------------------
# YAML loader
# ---------------------------------------------------------------------------

def _merge(base: dict, override: dict) -> dict:
    """Recursively merge *override* into *base*."""
    for k, v in override.items():
        if isinstance(v, dict) and isinstance(base.get(k), dict):
            _merge(base[k], v)
        else:
            base[k] = v
    return base


# Registry of known nested dataclass types for reliable resolution
_DATACLASS_REGISTRY: dict[str, type] = {
    "model": ModelConfig,
    "quantization": QuantizationConfig,
    "lora": LoraConfig,
    "training": TrainingConfig,
    "generation": GenerationConfig,
    "dataset": DatasetConfig,
    "evaluation": EvalConfig,
    "ui": UIConfig,
}


def _dict_to_dataclass(dc_cls: type, data: dict) -> Any:
    """Instantiate a nested dataclass hierarchy from a plain dict."""
    kwargs: dict[str, Any] = {}
    for key, value in data.items():
        if isinstance(value, dict) and key in _DATACLASS_REGISTRY:
            kwargs[key] = _dict_to_dataclass(_DATACLASS_REGISTRY[key], value)
        else:
            kwargs[key] = value
    return dc_cls(**kwargs)


def load_config(yaml_path: Optional[str | Path] = None) -> Config:
    """Load configuration from a YAML file, falling back to defaults."""
    if yaml_path is None:
        yaml_path = PROJECT_ROOT / "configs" / "default.yaml"
    path = Path(yaml_path)
    if path.exists():
        logger.info("Loading config from %s", path)
        with open(path, "r", encoding="utf-8") as fh:
            overrides = yaml.safe_load(fh) or {}
        # Build default dict, merge overrides, convert back
        import dataclasses

        base = dataclasses.asdict(Config())
        merged = _merge(base, overrides)
        return _dict_to_dataclass(Config, merged)
    logger.info("No config file found at %s – using defaults.", path)
    return Config()

Bug 2 – engine.py: Hardcoded torch.float16

Problem: Both bnb_4bit_compute_dtype and torch_dtype were hardcoded to torch.float16, ignoring YAML config values. This means switching to bfloat16 in config had no effect.

Fix: Added a local _resolve_dtype() helper that maps config strings to concrete torch.dtype values, including auto-detection of bf16 support.

"""Inference engine – load base model + LoRA adapter and generate optimised prompts.

Designed so that both the CLI script and the Gradio UI can reuse the same
``PromptOptimizer`` class without duplicating logic.
"""

from __future__ import annotations

import logging
from pathlib import Path
from typing import Optional

import torch
from peft import PeftModel
from transformers import (
    AutoModelForCausalLM,
    AutoTokenizer,
    BitsAndBytesConfig,
    PreTrainedTokenizerBase,
)

from src.config import Config, PROJECT_ROOT
from src.dataset.formatter import SYSTEM_MESSAGE

logger = logging.getLogger(__name__)


class PromptOptimizer:
    """Wraps model loading and generation behind a simple API."""

    def __init__(self, cfg: Config, adapter_path: Optional[Path] = None):
        self.cfg = cfg
        self._adapter_path = adapter_path or cfg.adapter_dir
        self.model, self.tokenizer = self._load()

    # ------------------------------------------------------------------
    # Model loading
    # ------------------------------------------------------------------
    def _load(self):
        bnb_config = BitsAndBytesConfig(
            load_in_4bit=self.cfg.quantization.load_in_4bit,
            bnb_4bit_quant_type=self.cfg.quantization.bnb_4bit_quant_type,
            bnb_4bit_compute_dtype=torch.float16,
            bnb_4bit_use_double_quant=self.cfg.quantization.bnb_4bit_use_double_quant,
        )

        logger.info("Loading base model: %s", self.cfg.model.name)
        base_model = AutoModelForCausalLM.from_pretrained(
            self.cfg.model.name,
            quantization_config=bnb_config,
            device_map="auto",
            trust_remote_code=self.cfg.model.trust_remote_code,
            torch_dtype=torch.float16,
        )

        tokenizer = AutoTokenizer.from_pretrained(
            self.cfg.model.name,
            trust_remote_code=self.cfg.model.trust_remote_code,
        )
        if tokenizer.pad_token is None:
            tokenizer.pad_token = tokenizer.eos_token

        adapter = Path(self._adapter_path)
        if adapter.exists():
            logger.info("Loading LoRA adapter from %s", adapter)
            model = PeftModel.from_pretrained(base_model, str(adapter))
        else:
            logger.warning(
                "Adapter not found at %s – running base model only.", adapter
            )
            model = base_model

        model.eval()
        return model, tokenizer

    # ------------------------------------------------------------------
    # Prompt construction using chat template
    # ------------------------------------------------------------------
    def _build_input(self, raw_prompt: str) -> str:
        """Format the user prompt using the tokenizer's chat template."""
        messages = [
            {"role": "system", "content": SYSTEM_MESSAGE},
            {"role": "user", "content": raw_prompt},
        ]
        try:
            return self.tokenizer.apply_chat_template(
                messages, tokenize=False, add_generation_prompt=True
            )
        except Exception:
            return (
                f"### System:\n{SYSTEM_MESSAGE}\n\n"
                f"### Instruction:\n{raw_prompt}\n\n"
                f"### Response:\n"
            )

    # ------------------------------------------------------------------
    # Generation
    # ------------------------------------------------------------------
    @torch.inference_mode()
    def optimize(
        self,
        raw_prompt: str,
        *,
        max_new_tokens: Optional[int] = None,
        temperature: Optional[float] = None,
        top_p: Optional[float] = None,
        repetition_penalty: Optional[float] = None,
        do_sample: Optional[bool] = None,
    ) -> str:
        """Generate an optimised prompt from a raw user prompt.

        Generation parameters fall back to ``self.cfg.generation`` defaults
        when not explicitly provided.
        """
        gen = self.cfg.generation
        max_new_tokens = max_new_tokens or gen.max_new_tokens
        temperature = temperature if temperature is not None else gen.temperature
        top_p = top_p if top_p is not None else gen.top_p
        repetition_penalty = repetition_penalty or gen.repetition_penalty
        do_sample = do_sample if do_sample is not None else gen.do_sample

        input_text = self._build_input(raw_prompt)
        inputs = self.tokenizer(input_text, return_tensors="pt").to(self.model.device)

        outputs = self.model.generate(
            **inputs,
            max_new_tokens=max_new_tokens,
            temperature=temperature,
            top_p=top_p,
            repetition_penalty=repetition_penalty,
            do_sample=do_sample,
            pad_token_id=self.tokenizer.pad_token_id,
        )

        # Decode only the newly generated tokens
        generated_ids = outputs[0][inputs["input_ids"].shape[-1]:]
        result = self.tokenizer.decode(generated_ids, skip_special_tokens=True).strip()
        return result


# ---------------------------------------------------------------------------
# Convenience function for one-off use
# ---------------------------------------------------------------------------

def optimize_prompt(
    raw_prompt: str,
    cfg: Optional[Config] = None,
    adapter_path: Optional[Path] = None,
) -> str:
    """Functional wrapper – loads the model once and returns the optimised prompt."""
    if cfg is None:
        from src.config import load_config
        cfg = load_config()
    engine = PromptOptimizer(cfg, adapter_path=adapter_path)
    return engine.optimize(raw_prompt)
===
"""Inference engine – load base model + LoRA adapter and generate optimised prompts.

Designed so that both the CLI script and the Gradio UI can reuse the same
``PromptOptimizer`` class without duplicating logic.
"""

from __future__ import annotations

import logging
from pathlib import Path
from typing import Optional

import torch
from peft import PeftModel
from transformers import (
    AutoModelForCausalLM,
    AutoTokenizer,
    BitsAndBytesConfig,
    PreTrainedTokenizerBase,
)

from src.config import Config, PROJECT_ROOT
from src.dataset.formatter import SYSTEM_MESSAGE

logger = logging.getLogger(__name__)


def _resolve_dtype(name: str) -> torch.dtype:
    """Map a config string to a concrete torch dtype."""
    mapping = {"float16": torch.float16, "bfloat16": torch.bfloat16}
    if name == "auto":
        return torch.bfloat16 if torch.cuda.is_available() and torch.cuda.is_bf16_supported() else torch.float16
    return mapping.get(name, torch.float16)


class PromptOptimizer:
    """Wraps model loading and generation behind a simple API."""

    def __init__(self, cfg: Config, adapter_path: Optional[Path] = None):
        self.cfg = cfg
        self._adapter_path = adapter_path or cfg.adapter_dir
        self.model, self.tokenizer = self._load()

    # ------------------------------------------------------------------
    # Model loading
    # ------------------------------------------------------------------
    def _load(self):
        compute_dtype = _resolve_dtype(self.cfg.quantization.bnb_4bit_compute_dtype)
        model_dtype = _resolve_dtype(self.cfg.model.torch_dtype)

        bnb_config = BitsAndBytesConfig(
            load_in_4bit=self.cfg.quantization.load_in_4bit,
            bnb_4bit_quant_type=self.cfg.quantization.bnb_4bit_quant_type,
            bnb_4bit_compute_dtype=compute_dtype,
            bnb_4bit_use_double_quant=self.cfg.quantization.bnb_4bit_use_double_quant,
        )

        logger.info("Loading base model: %s", self.cfg.model.name)
        base_model = AutoModelForCausalLM.from_pretrained(
            self.cfg.model.name,
            quantization_config=bnb_config,
            device_map="auto",
            trust_remote_code=self.cfg.model.trust_remote_code,
            torch_dtype=model_dtype,
        )

        tokenizer = AutoTokenizer.from_pretrained(
            self.cfg.model.name,
            trust_remote_code=self.cfg.model.trust_remote_code,
        )
        if tokenizer.pad_token is None:
            tokenizer.pad_token = tokenizer.eos_token

        adapter = Path(self._adapter_path)
        if adapter.exists():
            logger.info("Loading LoRA adapter from %s", adapter)
            model = PeftModel.from_pretrained(base_model, str(adapter))
        else:
            logger.warning(
                "Adapter not found at %s – running base model only.", adapter
            )
            model = base_model

        model.eval()
        return model, tokenizer

    # ------------------------------------------------------------------
    # Prompt construction using chat template
    # ------------------------------------------------------------------
    def _build_input(self, raw_prompt: str) -> str:
        """Format the user prompt using the tokenizer's chat template."""
        messages = [
            {"role": "system", "content": SYSTEM_MESSAGE},
            {"role": "user", "content": raw_prompt},
        ]
        try:
            return self.tokenizer.apply_chat_template(
                messages, tokenize=False, add_generation_prompt=True
            )
        except Exception:
            return (
                f"### System:\n{SYSTEM_MESSAGE}\n\n"
                f"### Instruction:\n{raw_prompt}\n\n"
                f"### Response:\n"
            )

    # ------------------------------------------------------------------
    # Generation
    # ------------------------------------------------------------------
    @torch.inference_mode()
    def optimize(
        self,
        raw_prompt: str,
        *,
        max_new_tokens: Optional[int] = None,
        temperature: Optional[float] = None,
        top_p: Optional[float] = None,
        repetition_penalty: Optional[float] = None,
        do_sample: Optional[bool] = None,
    ) -> str:
        """Generate an optimised prompt from a raw user prompt.

        Generation parameters fall back to ``self.cfg.generation`` defaults
        when not explicitly provided.
        """
        gen = self.cfg.generation
        max_new_tokens = max_new_tokens or gen.max_new_tokens
        temperature = temperature if temperature is not None else gen.temperature
        top_p = top_p if top_p is not None else gen.top_p
        repetition_penalty = repetition_penalty or gen.repetition_penalty
        do_sample = do_sample if do_sample is not None else gen.do_sample

        input_text = self._build_input(raw_prompt)
        inputs = self.tokenizer(input_text, return_tensors="pt").to(self.model.device)

        outputs = self.model.generate(
            **inputs,
            max_new_tokens=max_new_tokens,
            temperature=temperature,
            top_p=top_p,
            repetition_penalty=repetition_penalty,
            do_sample=do_sample,
            pad_token_id=self.tokenizer.pad_token_id,
        )

        # Decode only the newly generated tokens
        generated_ids = outputs[0][inputs["input_ids"].shape[-1]:]
        result = self.tokenizer.decode(generated_ids, skip_special_tokens=True).strip()
        return result


# ---------------------------------------------------------------------------
# Convenience function for one-off use
# ---------------------------------------------------------------------------

def optimize_prompt(
    raw_prompt: str,
    cfg: Optional[Config] = None,
    adapter_path: Optional[Path] = None,
) -> str:
    """Functional wrapper – loads the model once and returns the optimised prompt."""
    if cfg is None:
        from src.config import load_config
        cfg = load_config()
    engine = PromptOptimizer(cfg, adapter_path=adapter_path)
    return engine.optimize(raw_prompt)

Bug 3 – train.py: Mixed return type + deprecated API param

Problem: _resolve_dtype() returned "auto" (a string) for the auto case, but callers expected torch.dtype. Also, SFTTrainer used processing_class= which may not exist in older TRL versions.

Fix: _resolve_dtype("auto") now auto-detects bf16 support and returns a concrete dtype. Changed processing_class=tokenizertokenizer=tokenizer for broader compatibility.

"""Fine-tuning script – LoRA / QLoRA with SFTTrainer.

This module encapsulates:
- Model + tokenizer loading with 4-bit quantisation
- LoRA adapter configuration
- Dataset formatting via the tokenizer's chat template
- SFTTrainer initialisation and training loop
- Checkpoint & adapter saving
"""

from __future__ import annotations

import logging
from pathlib import Path
from typing import Optional

import torch
from datasets import DatasetDict
from peft import LoraConfig as PeftLoraConfig, get_peft_model, prepare_model_for_kbit_training
from transformers import (
    AutoModelForCausalLM,
    AutoTokenizer,
    BitsAndBytesConfig,
    TrainingArguments,
)
from trl import SFTTrainer

from src.config import Config, PROJECT_ROOT
from src.dataset.formatter import get_formatting_fn

logger = logging.getLogger(__name__)


# ---------------------------------------------------------------------------
# Hardware helpers
# ---------------------------------------------------------------------------

def _resolve_dtype(name: str) -> torch.dtype:
    mapping = {"float16": torch.float16, "bfloat16": torch.bfloat16, "auto": "auto"}
    return mapping.get(name, torch.float16)


def _detect_fp16_bf16(cfg: Config) -> tuple[bool, bool]:
    """Return (fp16, bf16) booleans depending on hardware + config."""
    if torch.cuda.is_available():
        if torch.cuda.is_bf16_supported():
            return False, True
        return True, False
    # CPU-only – disable both
    return False, False


# ---------------------------------------------------------------------------
# Model / tokenizer loading
# ---------------------------------------------------------------------------

def load_model_and_tokenizer(cfg: Config):
    """Load quantised base model and tokenizer."""
    bnb_config = BitsAndBytesConfig(
        load_in_4bit=cfg.quantization.load_in_4bit,
        bnb_4bit_quant_type=cfg.quantization.bnb_4bit_quant_type,
        bnb_4bit_compute_dtype=_resolve_dtype(cfg.quantization.bnb_4bit_compute_dtype),
        bnb_4bit_use_double_quant=cfg.quantization.bnb_4bit_use_double_quant,
    )

    logger.info("Loading model: %s", cfg.model.name)
    model = AutoModelForCausalLM.from_pretrained(
        cfg.model.name,
        quantization_config=bnb_config,
        device_map="auto",
        trust_remote_code=cfg.model.trust_remote_code,
        torch_dtype=_resolve_dtype(cfg.model.torch_dtype),
    )
    model = prepare_model_for_kbit_training(model)

    tokenizer = AutoTokenizer.from_pretrained(
        cfg.model.name,
        trust_remote_code=cfg.model.trust_remote_code,
    )
    # Ensure pad token exists (many models lack one)
    if tokenizer.pad_token is None:
        tokenizer.pad_token = tokenizer.eos_token
        model.config.pad_token_id = tokenizer.eos_token_id

    return model, tokenizer


# ---------------------------------------------------------------------------
# LoRA setup
# ---------------------------------------------------------------------------

def build_lora_config(cfg: Config) -> PeftLoraConfig:
    return PeftLoraConfig(
        r=cfg.lora.r,
        lora_alpha=cfg.lora.lora_alpha,
        lora_dropout=cfg.lora.lora_dropout,
        target_modules=cfg.lora.target_modules,
        bias=cfg.lora.bias,
        task_type=cfg.lora.task_type,
    )


# ---------------------------------------------------------------------------
# Training
# ---------------------------------------------------------------------------

def train(
    cfg: Config,
    dataset: DatasetDict,
    resume_from_checkpoint: Optional[str] = None,
) -> None:
    """Run the full fine-tuning pipeline."""

    model, tokenizer = load_model_and_tokenizer(cfg)
    lora_cfg = build_lora_config(cfg)
    model = get_peft_model(model, lora_cfg)
    model.print_trainable_parameters()

    fp16, bf16 = _detect_fp16_bf16(cfg)
    output_dir = str(PROJECT_ROOT / cfg.training.output_dir)

    training_args = TrainingArguments(
        output_dir=output_dir,
        num_train_epochs=cfg.training.num_train_epochs,
        per_device_train_batch_size=cfg.training.per_device_train_batch_size,
        gradient_accumulation_steps=cfg.training.gradient_accumulation_steps,
        learning_rate=cfg.training.learning_rate,
        weight_decay=cfg.training.weight_decay,
        warmup_ratio=cfg.training.warmup_ratio,
        lr_scheduler_type=cfg.training.lr_scheduler_type,
        logging_steps=cfg.training.logging_steps,
        save_strategy=cfg.training.save_strategy,
        save_total_limit=cfg.training.save_total_limit,
        fp16=fp16,
        bf16=bf16,
        gradient_checkpointing=cfg.training.gradient_checkpointing,
        optim=cfg.training.optim,
        report_to=cfg.training.report_to,
        seed=cfg.training.seed,
        remove_unused_columns=False,
    )

    # Format dataset via chat template
    formatting_fn = get_formatting_fn(tokenizer)
    train_ds = dataset["train"].map(formatting_fn)
    val_ds = dataset["validation"].map(formatting_fn) if "validation" in dataset else None

    trainer = SFTTrainer(
        model=model,
        args=training_args,
        train_dataset=train_ds,
        eval_dataset=val_ds,
        processing_class=tokenizer,
        dataset_text_field="text",
        max_seq_length=cfg.training.max_seq_length,
        packing=False,
    )

    logger.info("Starting training …")
    trainer.train(resume_from_checkpoint=resume_from_checkpoint)

    # Save adapter
    adapter_dir = str(cfg.adapter_dir)
    logger.info("Saving LoRA adapter to %s", adapter_dir)
    Path(adapter_dir).mkdir(parents=True, exist_ok=True)
    model.save_pretrained(adapter_dir)
    tokenizer.save_pretrained(adapter_dir)

    logger.info("Training complete.")
===
"""Fine-tuning script – LoRA / QLoRA with SFTTrainer.

This module encapsulates:
- Model + tokenizer loading with 4-bit quantisation
- LoRA adapter configuration
- Dataset formatting via the tokenizer's chat template
- SFTTrainer initialisation and training loop
- Checkpoint & adapter saving
"""

from __future__ import annotations

import logging
from pathlib import Path
from typing import Optional

import torch
from datasets import DatasetDict
from peft import LoraConfig as PeftLoraConfig, get_peft_model, prepare_model_for_kbit_training
from transformers import (
    AutoModelForCausalLM,
    AutoTokenizer,
    BitsAndBytesConfig,
    TrainingArguments,
)
from trl import SFTTrainer

from src.config import Config, PROJECT_ROOT
from src.dataset.formatter import get_formatting_fn

logger = logging.getLogger(__name__)


# ---------------------------------------------------------------------------
# Hardware helpers
# ---------------------------------------------------------------------------

def _resolve_dtype(name: str) -> torch.dtype:
    """Map a config string to a concrete torch dtype."""
    mapping = {"float16": torch.float16, "bfloat16": torch.bfloat16}
    if name == "auto":
        return torch.bfloat16 if torch.cuda.is_available() and torch.cuda.is_bf16_supported() else torch.float16
    return mapping.get(name, torch.float16)


def _detect_fp16_bf16(cfg: Config) -> tuple[bool, bool]:
    """Return (fp16, bf16) booleans depending on hardware + config."""
    if torch.cuda.is_available():
        if torch.cuda.is_bf16_supported():
            return False, True
        return True, False
    # CPU-only – disable both
    return False, False


# ---------------------------------------------------------------------------
# Model / tokenizer loading
# ---------------------------------------------------------------------------

def load_model_and_tokenizer(cfg: Config):
    """Load quantised base model and tokenizer."""
    bnb_config = BitsAndBytesConfig(
        load_in_4bit=cfg.quantization.load_in_4bit,
        bnb_4bit_quant_type=cfg.quantization.bnb_4bit_quant_type,
        bnb_4bit_compute_dtype=_resolve_dtype(cfg.quantization.bnb_4bit_compute_dtype),
        bnb_4bit_use_double_quant=cfg.quantization.bnb_4bit_use_double_quant,
    )

    logger.info("Loading model: %s", cfg.model.name)
    model = AutoModelForCausalLM.from_pretrained(
        cfg.model.name,
        quantization_config=bnb_config,
        device_map="auto",
        trust_remote_code=cfg.model.trust_remote_code,
        torch_dtype=_resolve_dtype(cfg.model.torch_dtype),
    )
    model = prepare_model_for_kbit_training(model)

    tokenizer = AutoTokenizer.from_pretrained(
        cfg.model.name,
        trust_remote_code=cfg.model.trust_remote_code,
    )
    # Ensure pad token exists (many models lack one)
    if tokenizer.pad_token is None:
        tokenizer.pad_token = tokenizer.eos_token
        model.config.pad_token_id = tokenizer.eos_token_id

    return model, tokenizer


# ---------------------------------------------------------------------------
# LoRA setup
# ---------------------------------------------------------------------------

def build_lora_config(cfg: Config) -> PeftLoraConfig:
    return PeftLoraConfig(
        r=cfg.lora.r,
        lora_alpha=cfg.lora.lora_alpha,
        lora_dropout=cfg.lora.lora_dropout,
        target_modules=cfg.lora.target_modules,
        bias=cfg.lora.bias,
        task_type=cfg.lora.task_type,
    )


# ---------------------------------------------------------------------------
# Training
# ---------------------------------------------------------------------------

def train(
    cfg: Config,
    dataset: DatasetDict,
    resume_from_checkpoint: Optional[str] = None,
) -> None:
    """Run the full fine-tuning pipeline."""

    model, tokenizer = load_model_and_tokenizer(cfg)
    lora_cfg = build_lora_config(cfg)
    model = get_peft_model(model, lora_cfg)
    model.print_trainable_parameters()

    fp16, bf16 = _detect_fp16_bf16(cfg)
    output_dir = str(PROJECT_ROOT / cfg.training.output_dir)

    training_args = TrainingArguments(
        output_dir=output_dir,
        num_train_epochs=cfg.training.num_train_epochs,
        per_device_train_batch_size=cfg.training.per_device_train_batch_size,
        gradient_accumulation_steps=cfg.training.gradient_accumulation_steps,
        learning_rate=cfg.training.learning_rate,
        weight_decay=cfg.training.weight_decay,
        warmup_ratio=cfg.training.warmup_ratio,
        lr_scheduler_type=cfg.training.lr_scheduler_type,
        logging_steps=cfg.training.logging_steps,
        save_strategy=cfg.training.save_strategy,
        save_total_limit=cfg.training.save_total_limit,
        fp16=fp16,
        bf16=bf16,
        gradient_checkpointing=cfg.training.gradient_checkpointing,
        optim=cfg.training.optim,
        report_to=cfg.training.report_to,
        seed=cfg.training.seed,
        remove_unused_columns=False,
    )

    # Format dataset via chat template
    formatting_fn = get_formatting_fn(tokenizer)
    train_ds = dataset["train"].map(formatting_fn)
    val_ds = dataset["validation"].map(formatting_fn) if "validation" in dataset else None

    trainer = SFTTrainer(
        model=model,
        args=training_args,
        train_dataset=train_ds,
        eval_dataset=val_ds,
        tokenizer=tokenizer,
        dataset_text_field="text",
        max_seq_length=cfg.training.max_seq_length,
        packing=False,
    )

    logger.info("Starting training …")
    trainer.train(resume_from_checkpoint=resume_from_checkpoint)

    # Save adapter
    adapter_dir = str(cfg.adapter_dir)
    logger.info("Saving LoRA adapter to %s", adapter_dir)
    Path(adapter_dir).mkdir(parents=True, exist_ok=True)
    model.save_pretrained(adapter_dir)
    tokenizer.save_pretrained(adapter_dir)

    logger.info("Training complete.")

Bug 4 – requirements.txt: Missing matplotlib

torch>=2.1.0
transformers>=4.40.0
datasets>=2.18.0
peft>=0.10.0
trl>=0.8.0
accelerate>=0.28.0
bitsandbytes>=0.43.0
sentencepiece>=0.2.0
protobuf>=4.25.0
gradio>=4.20.0
pyyaml>=6.0
===
torch>=2.1.0
transformers>=4.40.0
datasets>=2.18.0
peft>=0.10.0
trl>=0.8.0
accelerate>=0.28.0
bitsandbytes>=0.43.0
sentencepiece>=0.2.0
protobuf>=4.25.0
gradio>=4.20.0
pyyaml>=6.0
matplotlib>=3.7.0

Files Verified as Correct (18 files, no changes needed)

File Status
src/init.py ✅ Verified
src/dataset/init.py ✅ Verified
src/dataset/seeds.py ✅ Verified
src/dataset/generator.py ✅ Verified
src/dataset/formatter.py ✅ Verified
src/evaluation/init.py ✅ Verified
src/inference/init.py ✅ Verified
src/training/init.py ✅ Verified
src/utils/init.py ✅ Verified
app/init.py ✅ Verified
configs/default.yaml ✅ Verified
scripts/generate_dataset.py ✅ Verified
scripts/train.py ✅ Verified
scripts/infer.py ✅ Verified
scripts/evaluate.py ✅ Verified
scripts/launch_ui.py ✅ Verified
README.md ✅ Verified
.gitignore ✅ Verified

Phase 2: Compression Graph Feature

metrics.py

Added two visualization functions (all original functions preserved):

  • generate_compression_chart(metrics) – single-prompt bar chart with annotation arrow showing tokens saved and % reduction
  • generate_batch_compression_chart(results) – grouped bar chart for batch evaluation

ui.py

  • Added gr.Plot() component below the metrics section
  • run_optimization() now returns 7 values (was 6), including the matplotlib Figure
  • Added CSS styling and UI polish

Phase 3: Deployment Guide

Created DEPLOYMENT.md covering:

  • GCP Compute Engine setup with L4/T4 GPU
  • Complete Dockerfile and Docker Compose
  • Vertex AI deployment with custom prediction server
  • Nginx + SSL reverse proxy for secure exposure
  • systemd auto-restart and monitoring

Phase 4: Research Paper Outline

Created PAPER_OUTLINE.md with:

  • 11-section professional structure (Abstract → Appendix)
  • Formal problem definition and methodology
  • Evaluation metrics framework (automated + manual)
  • 5 ablation study suggestions
  • LaTeX template header
  • 10 key references to cite

Validation

All 5 modified Python files pass py_compile:

python -m py_compile src/config.py       ✅
python -m py_compile src/evaluation/metrics.py  ✅
python -m py_compile src/training/train.py      ✅
python -m py_compile src/inference/engine.py    ✅
python -m py_compile app/ui.py                  ✅