PyTorch Conference Europe 2026

Distributed PyTorch training often looks healthy in system dashboards; GPU utilization is high, memory is stable and yet throughput degrades, steps jitter, or GPUs go idle intermittently. The core issue is misalignment: most
telemetry is sampled by time, while training progresses by "steps", and distributed behavior is dominated by the slowest rank rather than averages.

In this talk I will breaks down common failure modes in DDP training that standard metrics miss (rank stragglers, dataloader stalls, step-time variance, and memory spikes/creep). We will show how step-aligned, rank-aware aggregation changes debugging: per-step worst-rank vs median-rank views, gating to completed steps across ranks, and how to tie time and memory back to training semantics without relying on heavyweight profilers.

The Hopper generation of NVIDIA GPUs first enabled the use of low-precision float8 data types for training via TensorCore acceleration. However, the recipe to best leverage it was far from settled. Practitioners had to find their way through many entangled decisions around accuracy-vs-efficiency, precision-vs-range, overflows-vs-underflows, and more. The frontier was further push forward by the DeepSeek release, and then by the micro-scaling formats introduced by Blackwell. In this talk we will go through all these approaches, comparing their pros and cons, thus guiding researchers in finding the options that work best for them.

Deploying massive Mixture-of-Experts (MoE) architectures like DeepSeek-V3/R1 requires a co-designed approach leveraging NVIDIA Blackwell’s fifth-generation Tensor Cores. This session details the transition to NVFP4 precision for MoE weights to significantly reduce memory load, coupled with FP4/FP8 KV caching to minimize attention layer footprint and enable higher concurrency.
We will analyze the architectural shift to Expert Parallelism (EP) for expert layers to maximize FLOPS, and Attention Data Parallelism (ADP) for attention heads—avoiding redundant KV replication and converting Multi-Head Latent Attention (MLA) into Multi-Query Attention (MQA) via weight absorption. The talk will demonstrate advanced execution strategies, including DualPipe algorithms to overlap dispatch/combine communication with computation, and the integration of DeepGEMM and FlashInfer kernels. Finally, we will cover runtime optimizations using Programmatic Dependent Launch (PDL) and CUDA Graphs to minimize host latency, alongside Multi-Token Prediction (MTP) for accelerated speculative decoding.

We will share the latest updates to NCCL and how they can be used in PyTorch. We invite the community to share their feedback on challenges using NCCL at scale and ways to improve integration of NCCL with PyTorch applications.

Some of the important topics for community discussion include:
- Symmetric memory support and GPU-initiated networking.
- Copy-engine collectives and maximizing overlap of communication and computation for better end-to-end performance.
- Profiling, debugging and tuning, as well as resilience (handling failed nodes without a restart).

The DeepSeek-V3 paper describes 5D parallelism and DualPipe at a high level, but leaves critical implementation details undocumented. This session presents our open-source PyTorch reference implementation that fills those gaps - verified against the original architecture and designed for learning and extension.

We'll share what we discovered building it from scratch:
Why K_pe is shared across heads in decoupled RoPE (not explicit in paper)
The critical timing of bias updates in auxiliary-loss-free load balancing
How sigmoid routing separates selection scores from gate values
The warmup formula that makes DualPipe achieve 3% bubble overhead
Bugs we caught: causal mask position offsets, EMA initialization, capacity dropping priority

What you'll learn:

5D Parallelism: How TP, PP, DP, EP, and SP interact at 2,048+ GPU scale
DualPipe: Building the bidirectional scheduler with 55% throughput gain over GPipe
Hierarchical All-to-All: Two-level communication reducing MoE dispatch overhead by 4x
Teachable abstractions: CapacityMetrics, ExpertSpecializationTracker, ScheduleStep enums

Prerequisites: torch.distributed basics.
Code: github.com/DevJadhav/deepseek-from-scratch