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    30 min
    Lesson 2 of 4

    Optimizing AI Workloads on Blackwell

    From the course NVIDIA Blackwell Architecture

    Leverage Blackwell's capabilities for maximum performance in training and inference workloads.

    Training Optimization

    Mixed-Precision Training

    import torch
    from torch.cuda.amp import autocast, GradScaler
    
    # Automatic Mixed Precision on Blackwell
    scaler = GradScaler()
    
    for data, target in dataloader:
        optimizer.zero_grad()
        
        # FP8 forward pass (Blackwell Transformer Engine)
        with autocast(dtype=torch.float8_e4m3fn):
            output = model(data)
            loss = criterion(output, target)
        
        # Scaled backward pass
        scaler.scale(loss).backward()
        scaler.step(optimizer)
        scaler.update()
    

    Distributed Training

    import torch.distributed as dist
    from torch.nn.parallel import DistributedDataParallel as DDP
    
    # Initialize distributed training across Blackwell GPUs
    dist.init_process_group(backend='nccl')
    local_rank = int(os.environ['LOCAL_RANK'])
    torch.cuda.set_device(local_rank)
    
    model = YourModel().to(local_rank)
    model = DDP(model, device_ids=[local_rank])
    
    # NVLink-optimized gradient synchronization
    for data, target in dataloader:
        output = model(data)
        loss = criterion(output, target)
        loss.backward()  # Gradients synced via NVLink
        optimizer.step()
    

    Inference Optimization

    FP4 Quantization

    from transformers import AutoModelForCausalLM, AutoTokenizer
    import torch
    
    # Load model with FP4 quantization (Blackwell-optimized)
    model = AutoModelForCausalLM.from_pretrained(
        "meta-llama/Llama-3-70b",
        torch_dtype=torch.float8_e4m3fn,  # FP4/FP8 mode
        device_map="auto",
        load_in_4bit=True
    )
    
    tokenizer = AutoTokenizer.from_pretrained("meta-llama/Llama-3-70b")
    
    # 4x faster inference on Blackwell
    inputs = tokenizer("Generate a summary:", return_tensors="pt").to("cuda")
    outputs = model.generate(**inputs, max_length=500)
    

    TensorRT-LLM Deployment

    import tensorrt_llm
    from tensorrt_llm.runtime import ModelRunner
    
    # Compile model for Blackwell optimizations
    engine = tensorrt_llm.build(
        model_path="llama-70b",
        dtype="fp8",  # Blackwell FP8 precision
        max_batch_size=32,
        max_input_len=8192,  # Extended context on Blackwell
        max_output_len=2048,
        use_gpt_attention_plugin=True,  # Transformer Engine
        use_gemm_plugin=True
    )
    
    runner = ModelRunner.from_engine(engine)
    outputs = runner.generate(input_tokens, max_new_tokens=100)
    

    Memory Optimization

    Gradient Checkpointing

    from torch.utils.checkpoint import checkpoint
    
    # Reduce memory usage for large models
    class OptimizedTransformer(nn.Module):
        def forward(self, x):
            # Checkpoint layers to trade compute for memory
            for layer in self.layers:
                x = checkpoint(layer, x)
            return x
    

    Flash Attention 3

    from flash_attn import flash_attn_func
    
    # Blackwell-optimized attention (built into Transformer Engine)
    attn_output = flash_attn_func(
        q, k, v,
        dropout_p=0.1,
        softmax_scale=None,
        causal=True,
        window_size=(-1, -1),  # Full attention
        alibi_slopes=None
    )
    

    Key Takeaways

    • •Mixed-precision training with FP8/FP4 delivers 2-4x speedup on Blackwell
    • •Distributed training via NVLink enables efficient multi-GPU model parallelism
    • •TensorRT-LLM compiles models for Blackwell's Transformer Engine optimizations
    • •Flash Attention 3 and gradient checkpointing maximize memory efficiency
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