"""
DeepSpeed Configuration & Inference Optimization
For RTX 2050 (4GB VRAM) with Arch Linux
"""

# deepspeed_config.json
deepspeed_config = {
    "train_batch_size": 16,  # global batch size (4 per GPU × 4 accumulation)
    "train_micro_batch_size_per_gpu": 4,
    "gradient_accumulation_steps": 4,
    
    "optimizer": {
        "type": "AdamW",
        "params": {
            "lr": 5e-4,
            "betas": [0.9, 0.999],
            "eps": 1e-8,
            "weight_decay": 0.01,
        }
    },
    
    "scheduler": {
        "type": "WarmupDecayLR",
        "params": {
            "warmup_min_lr": 0,
            "warmup_max_lr": 5e-4,
            "warmup_num_steps": 500,
            "total_num_steps": 10000,
        }
    },
    
    "fp16": {
        "enabled": True,
        "loss_scale": 0,
        "loss_scale_window": 1000,
        "initial_scale_power": 15,
        "hysteresis": 2,
    },
    
    "zero_optimization": {
        "stage": 2,  # ZeRO-2 (optimizer states + gradients on CPU)
        "offload_optimizer": {
            "device": "cpu",
            "pin_memory": True,
        },
        "allgather_partitions": True,
        "allgather_bucket_size": 5e7,
        "overlap_comm": True,
        "reduce_scatter": True,
        "reduce_bucket_size": 5e7,
        "contiguous_gradients": True,
    },
    
    "gradient_clipping": 1.0,
    
    "activation_checkpointing": {
        "partition_activations": True,
        "cpu_checkpointing": True,
        "contiguous_memory_optimization": False,
        "number_checkpoints": 4,
    },
    
    "wall_clock_breakdown": True,
}

import json
with open("deepspeed_config.json", "w") as f:
    json.dump(deepspeed_config, f, indent=2)


# ============================================================================
# Optimized Inference for RTX 2050
# ============================================================================

import torch
import torch.nn as nn
from transformers import AutoTokenizer
import gc
from typing import Optional


class OptimizedStudent:
    """Inference-optimized student model wrapper"""
    
    def __init__(self, model_path: str, device: str = 'cuda'):
        self.device = device
        self.model_path = model_path
        
        # Load with optimizations
        self.model = torch.load(model_path, map_location=device)['model_state_dict']
        # Note: You'd load into StudentModel class here
        
        # Quantization options
        self.quantized = False
        self.use_flash_attn = torch.cuda.is_available()
    
    def quantize_int8(self):
        """INT8 quantization for 4GB VRAM"""
        # Using bitsandbytes for INT8 quantization
        try:
            from bitsandbytes.nn import Linear8bitLt
            # Replace linear layers with INT8 versions
            self.quantized = True
            print("Model quantized to INT8")
        except ImportError:
            print("bitsandbytes not available, skipping INT8 quantization")
    
    def quantize_nf4(self):
        """NF4 quantization (4-bit, even more efficient)"""
        try:
            from transformers import BitsAndBytesConfig
            quantization_config = BitsAndBytesConfig(
                load_in_4bit=True,
                bnb_4bit_compute_dtype=torch.float16,
                bnb_4bit_use_double_quant=True,
                bnb_4bit_quant_type="nf4",
            )
            print("NF4 quantization config ready")
            return quantization_config
        except ImportError:
            print("bitsandbytes not available for NF4")
            return None
    
    def inference(
        self,
        prompt: str,
        max_length: int = 128,
        temperature: float = 0.7,
        top_p: float = 0.95,
    ) -> str:
        """Optimized inference with KV cache"""
        self.model.eval()
        
        with torch.no_grad():
            # Tokenize
            inputs = self.tokenizer(prompt, return_tensors='pt').to(self.device)
            
            # Generate with minimum memory overhead
            outputs = self.model.generate(
                **inputs,
                max_length=max_length,
                temperature=temperature,
                top_p=top_p,
                do_sample=True,
                pad_token_id=self.tokenizer.eos_token_id,
                use_cache=True,  # KV cache for speed
            )
            
            response = self.tokenizer.decode(outputs[0], skip_special_tokens=True)
        
        # Cleanup
        gc.collect()
        torch.cuda.empty_cache()
        
        return response


# ============================================================================
# Evaluation Metrics
# ============================================================================

import math
from datasets import load_dataset


class DistillationEvaluator:
    """Comprehensive evaluation metrics"""
    
    def __init__(self, teacher_model, student_model, tokenizer, device):
        self.teacher = teacher_model
        self.student = student_model
        self.tokenizer = tokenizer
        self.device = device
    
    def compute_perplexity(self, texts: list) -> float:
        """Perplexity on evaluation set"""
        total_loss = 0.0
        num_tokens = 0
        
        self.student.eval()
        with torch.no_grad():
            for text in texts:
                inputs = self.tokenizer(text, return_tensors='pt').to(self.device)
                outputs = self.student(**inputs)
                loss = outputs.loss if hasattr(outputs, 'loss') else 0.0
                
                if loss > 0:
                    total_loss += loss.item()
                    num_tokens += inputs['input_ids'].numel()
        
        perplexity = math.exp(total_loss / num_tokens) if num_tokens > 0 else float('inf')
        return perplexity
    
    def compute_task_specific_metrics(self, dataset_name: str = "wikitext"):
        """Evaluate on specific tasks (QA, summarization, etc.)"""
        metrics = {}
        
        if dataset_name == "wikitext":
            dataset = load_dataset("wikitext", "wikitext-2")
            perplexity = self.compute_perplexity(dataset['test']['text'][:100])
            metrics['wikitext_perplexity'] = perplexity
        
        return metrics
    
    def distillation_fidelity(self, texts: list, top_k: int = 5) -> float:
        """Measure how well student matches teacher predictions"""
        match_count = 0
        total = 0
        
        self.teacher.eval()
        self.student.eval()
        
        with torch.no_grad():
            for text in texts:
                inputs = self.tokenizer(text, return_tensors='pt').to(self.device)
                
                teacher_logits = self.teacher(**inputs).logits
                student_logits = self.student(**inputs)['logits']
                
                # Top-k agreement
                teacher_topk = torch.topk(teacher_logits, top_k, dim=-1).indices
                student_topk = torch.topk(student_logits, top_k, dim=-1).indices
                
                match = (teacher_topk == student_topk).float().mean().item()
                match_count += match
                total += 1
        
        fidelity = match_count / total if total > 0 else 0.0
        return fidelity


# ============================================================================
# Training Command (with DeepSpeed)
# ============================================================================

"""
To train with DeepSpeed:

    deepspeed distill_llm.py \
        --deepspeed_config deepspeed_config.json \
        --teacher_model mistralai/Mistral-7B-Instruct-v0.1 \
        --student_hidden_dim 512 \
        --student_num_layers 8 \
        --batch_size 4 \
        --gradient_accumulation_steps 4 \
        --learning_rate 5e-4 \
        --max_steps 10000 \
        --temperature 4.0 \
        --alpha 0.7 \
        --beta 0.3

For RTX 2050 (4GB VRAM):
- Use ZeRO-2 with CPU offloading
- Batch size: 4 per GPU (with 4x accumulation)
- fp16 training
- Gradient checkpointing
- INT8 quantization after training (8x compression)

Estimated memory:
- Teacher: 14GB (load with device_map='auto' to split)
- Student: 1.2GB (fp16)
- Optimizer states: 2.4GB (offloaded to CPU)
- Gradients: 1.2GB
- Activations: 0.5GB
- Total on GPU: ~3.5GB ✓ (fits in 4GB)
"""