arXiv AI

Echo: Error-Compensated 4-Bit Tensor-Parallel Communication for LLM Training and Inference

arXiv Machine Learning
Sep 23

Accelerating the Mitigation of LLM Inference Nondeterminism Across GPU Architectures

The paper addresses the problem of non‑deterministic outputs from large language models (LLMs) when run on different GPU architectures, caused by floating‑point non‑associativity and hardware‑dependent kernel choices. It proposes a set of fixed‑configuration fused‑upcast GEMM kernels that load 16‑bit weights, upcast to FP32, and perform IEEE‑754 compliant reductions in a problem‑shape‑dependent order, ensuring identical linear‑layer outputs across NVIDIA Ampere, Ada, and Hopper GPUs. The new approach achieves 1.17–3.1× faster end‑to‑end performance than existing solutions and halves weight‑memory traffic while maintaining cross‑architecture reproducibility.

By Liam Cooper, Shinnung Jeong, Hyeran Jeon, Jeffrey Young, Hyesoon Kim
arXiv AI
Aug 28

Pushing the Envelope of LLM Inference with Ultra-Low-Bit Quantized Models

The paper reports the development of 2‑bit microkernels for CPUs and mixed‑precision 2‑bit kernels for Intel Xe2 GPUs, achieving near‑roofline performance. Integrated into LLM inference pipelines, these kernels deliver up to 7× speedup over 16‑bit inference on CPUs and 6.7× on GPUs, surpassing the current state‑of‑the‑art bitnet.cpp runtime by 2.2×. The work demonstrates that ultra‑low‑bit LLM models can be deployed efficiently, offering significant gains in latency, memory, throughput, and energy consumption.

By Evangelos Georganas, Dhiraj Kalamkar, Alexander Heinecke, Pradeep Dubey
arXiv Machine Learning
3d ago

Is 2:4 Sparsity Still Worth It? Semi-Structured Sparsity versus Quantization in LLM Inference

The paper evaluates NVIDIA’s 2:4 semi‑structured sparsity against quantization for large language model inference. Experiments across multiple GPU generations and transformer GEMM operands show that when lower precision is available, adding 2:4 sparsity degrades accuracy and speed compared to simply reducing precision. However, at the lowest supported precision, 2:4 sparsity still yields a 1.3–1.7× speedup, and a retrained 2:4 model on an H100 achieves 27 % higher prefill throughput than a dense FP8 model while maintaining GSM8K accuracy.

By Xiuyi Qin
arXiv Machine Learning
Oct 3

Format-Aware Fusion for Fast FP4 Pretraining

The paper introduces format‑aware fusion, a method that co‑designs quantization producers with their scale domains and consumer layouts to fully exploit four‑bit floating‑point (FP4) Tensor Cores. Using this approach, the authors pretrain the Llama‑3‑family 8B model on 160 billion tokens, achieving up to 37.9 K tokens/s/GPU—significantly higher than standard bfloat16 or Transformer Engine FP4 baselines. The study demonstrates that FP4 performance depends on the interplay of scaling, operand packing, layout, and execution path, with downstream task rankings diverging from training‑loss rankings.

By Robert Hu
arXiv Machine Learning
Sep 24

Silent Failures Beyond the 32-Bit Index Range: A Differential Characterization of Large-Tensor Matrix Multiplication in PyTorch's MPS Backend

Apple Silicon machines with large unified memory allow large tensors on a desktop GPU, but PyTorch’s Metal Performance Shaders (MPS) backend silently returns incorrect results for batched matrix multiplication when the output exceeds $2^{32}$ elements. The authors swept over dtypes, memory layouts, shapes, and batch sizes around $2^{31}$ and $2^{32}$ elements, finding that errors arise when operands are transposed views or when contiguous inputs exceed $2^{32}$ elements, with the backward pass also affected. They reproduced the issue on multiple machines and macOS versions, confirmed correct behavior on an NVIDIA A100, and demonstrated real‑world impact in a sentiment classifier, releasing a harness and guard to prevent such silent failures.

By Junichiro Niimi
arXiv Machine Learning
Jul 3

SCAPE: Accurate and Efficient LLM Training with Extreme Sparse Communication

arXiv:2607. 01678v1 Announce Type: new Abstract: Communication increasingly dominates the cost of Large Language Model (LLM) pre-training, especially under data-parallel and sharded training schemes, where gradient synchronization and parameter reconstruction overhead increase with model size and system scale.

By Mingkai Zheng, Junlin Chen, Haotian Xie, Zhao Zhang
arXiv AI
Oct 9

The Missing Fourth Term for the Emulation Tensor Memory Equilibrium (TME) Model: The Residue Deconstruction Cost

The paper identifies a missing cost term in the Tensor‑Memory Equilibrium (TME) model for emulating fp64 on GPUs: the per‑input deconstruction cost required before matrix multiplication can proceed. By adding this term and calibrating it against cuBLAS, the authors derive a closed‑form operational‑intensity threshold (OI*) below which emulation cannot match native fp64 performance. On an NVIDIA B300 GPU, this threshold is about 0.56 FLOP/B, limiting the speed‑ups of memory‑bound kernels such as GEMV, SpMV, and low‑batch GEMV to 0.3–0.9× native, and reducing the 7‑point stencil speed‑up from 3.1× to 1.8×, while dense GEMM remains unaffected.

By Harun Bayraktar, John Gunnels, Peter Caday