What problem does it solve? Pretraining LLMs from scratch at 8B to 405B+ scale requires coordinating FSDP2, tensor, pipeline, and context parallelism across hundreds of GPUs, plus checkpointing, Float8 quantization, and SLURM orchestration, which is complex to configure correctly. ## Core Features & Use Cases - Composable 4D Parallelism: Configure FSDP2, tensor parallel, pipeline parallel, and context parallel degrees for models from 8B to 405B on single nodes or 512-GPU clusters. - Float8 and Compile Acceleration: Enable Float8 rowwise scaling with torch.compile for up to 48% throughput gains on H100 GPUs. - Checkpoint Management: Use PyTorch Distributed Checkpoint for async saves, seed checkpoints for pipeline parallelism, and HuggingFace/torchtune conversion. - Use Case: Pretrain Llama 3.1 8B on 8 GPUs by downloading the tokenizer, selecting the llama3_8b config from the registry, and launching with run_train.sh while monitoring TensorBoard logs. ## Quick Start Ask the agent to pretrain a Llama 3.1 8B model on 8 GPUs using TorchTitan with the llama3_8b config and checkpointing every 500 steps.