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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