arXiv AI

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.

arXiv AI
Sep 11

FP8 is All You Need (Part 1): Debunking Hardware FP64 as the HPC Holy Grail (Sep 3rd version)

The article argues that on AI‑optimised NVIDIA B300 GPUs and newer, the FP8 tensor‑core matrix operation—implemented via the CRT‑based Ozaki Scheme II—can become the primary substrate for matrix‑heavy FP64 kernels while maintaining FP64‑grade accuracy. It introduces the Tensor‑Memory Equilibrium (TME) model, a Roofline extension with four parameters, to show that FP8 can match native FP64 performance under certain intensity thresholds and tile‑fusion conditions. The study identifies two notable exceptions—large dense‑square DGEMM and 3‑D FFT—where additional hardware or software adjustments are required to reach the memory roof. whyItMatters":"The paper demonstrates that FP8, with appropriate reconstruction and deconstruction strategies, can replace native FP64 for high‑performance computing workloads on modern GPUs, potentially reducing hardware complexity and energy consumption while preserving accuracy."

By Satoshi Matsuoka
arXiv AI
Sep 11

FP8 is All You Need (Part 2): Full-FP64 3-D FFT on FP8-Generation Tensor CoresThe Integer-Epilogue Wall and the Minimal Hardware That Would Remove It

The paper presents a design for executing a full‑FP64 1024³ 3‑D FFT on NVIDIA’s Blackwell Ultra (B300) GPU using FP8 tensor cores. It replaces traditional FP64 arithmetic with a sequence of FP8‑tensor DFT GEMMs, Karatsuba‑based residue combination, and exact CRT reconstruction, leaving only a final conversion for rounding. The main bottleneck identified is a per‑output integer epilogue that limits performance to 63–87 ms, far above the theoretical 12.9 ms roof, and the authors propose modest hardware changes—such as an INT8 tensor core and cross‑column accumulation—to reduce this gap.

By Satoshi Matsuoka
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 26

More GPUs or a Smaller Cache? Tensor Parallelism versus KV Compression for Memory-Bound LLM Serving

The paper compares two strategies for handling memory limits in large language model (LLM) serving: tensor parallelism, which distributes weights and KV cache across multiple GPUs, and KV compression, which reduces cache size via quantisation and eviction on a single GPU. Using a cost‑normalised simulator calibrated on A100, A40, and H100 hardware, the authors find that across two models (Llama‑2 7B and 70B) and various GPU configurations, compression consistently outperforms tensor parallelism in cost per million tokens, offering 1.20× to 2.00× savings. The study identifies a model‑size threshold (~36B parameters on an 80 GB card) where compression dominates, while tensor parallelism becomes necessary only for larger models where weights alone exceed a single GPU’s capacity.

By Srikanta Datta Tumkur, Mehar Simhadri, Anshu Bansal, Jay Iyer, Sai Pavan Kumar, Sai Kapil Kumar, Ramesh Nampelly, Raj Dandekar
arXiv Machine Learning
5d ago

Memory Bandwidth, Not FLOPs: Profiling and Accelerating Query-Based Segmentation Decoders on Edge GPUs

The paper shows that query‑based segmentation decoders on edge GPUs are limited by memory bandwidth rather than FLOPs. Profiling reveals that non‑tensor‑core operations consume a large fraction of decoder time and bytes, saturating the DRAM bus. CompactInst mitigates this by using parameter‑free spatial pooling and a lightweight refinement head, achieving significant speedups on Jetson Orin Nano while maintaining accuracy.

By Oliver Busemann (Osnabr\"uck University, CLAAS E-Systems GmbH), Torben T\"oniges (CLAAS E-Systems GmbH), Martin Atzmueller (Semantic Information Systems Group, Osnabr\"uck University, German Research Center for Artificial Intelligence)