Distributed Computing
Consensus-based Decentralized Distributed Swarm Learning with Heterogeneous Big Data
Zhuoyu Yao, Dong Yang, Yue Wang et al. (+4 more)
Artificial intelligence increasingly relies on large-scale, distributed, and heterogeneous data collected by edge devices. However, the practice of edge intelligence remains challenging due to non-convex objectives, data heterogeneity, and complex wireless network
topology. To address these issues, this paper proposes a consensus-based decentralized distributed swarm learning (CD-DSL) framework for wireless edge networks. Our CD-DSL integrates consensus optimization with particle swarm optimization (PSO), by reaching the model consensus among neighboring devices while leveraging the PSO exploration and exploitation. The consensus mechanism supports decentralized coordination without raw-data exchange, while PSO-inspired updates utilize historical and neighbor-shared experience to enhance exploration for non-convex optimization, improve robustness to data heterogeneity, and accelerate convergence. We further develop an adaptive neighbor-mixing strategy that learns performance-aware consensus weights, improving decentralized collaboration among heterogeneous edge devices. Theoretical analysis establishes that CD-DSL maintains participant consistency and achieves non-ergodic convergence to a neighborhood of a stationary point under non-convex objectives. Experimental results show that CD-DSL can mitigate the performance degeneration of existing decentralized baselines caused by heterogeneous data.
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All authors Zhuoyu Yao, Dong Yang, Yue Wang, Songyang Zhang, Yingshu Li, Zhi Tian, Zhipeng Cai
Distributed Computing
Shards on a Shoestring: Empirical Characterization of NEAR Protocol Nightshade Sharding on Commodity Hardware
Sohini Sahukar, Om Amit Gandhi and Ioan Raicu
NEAR Protocol's Nightshade architecture targets one million transactions per second (TPS) through horizontal sharding of both state and computation. Published
benchmarks were produced on expensive Google Cloud Platform infrastructure costing approximately \$700 per hour, leaving a significant reproducibility gap for academic research. We present the first independent empirical characterization of NEAR Nightshade sharding on commodity hardware: a Chameleon Cloud bare-metal node with 48 hyperthreaded Intel Xeon cores, 128\,GB RAM, and HDD storage at 80--100\,MB/s. We systematically sweep shard count from $N{=}1$ to $N{=}24$, measuring aggregate TPS, per-shard TPS, block time, BFT finality, memory, and disk I/O. We identify three distinct bottleneck regimes: L3 cache pressure at low $N$, witness gossip pipeline saturation at mid $N$, and coherence collapse at high $N$. A key unexpected finding is that HDD write latency acts as implicit flow control for the witness gossip pipeline. Removing it via RAM-backed tmpfs causes complete chain stall at $N{=}16$, with a 29$\times$ spike in orphan witness rate at 47\% CPU utilization. Aggregate TPS peaks at $N{=}8$ (+40\% over $N{=}1$) then reverses, with per-shard TPS collapsing 23$\times$ by $N{=}24$. Our
dataset provides the first commodity-hardware calibration baseline for the companion SimPy sharding simulator.
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Distributed Computing
Efficient Vision-Language-Action Management and Serving for Robot Factories
Dionysios Adamopoulos, Nattapol Chanpaisit, Basel Fakhri et al. (+1 more)
Vision-
Language-Action (VLA) models show high robotic manipulation capabilities via a two-stage design: a
Vision-
Language Model (VLM) stage followed by an Action
Diffusion Transformer (ADiT) stage. Since
robots must meet strict Service-Level Objectives (SLOs) for safety, VLA inference is inherently latency-critical. Meeting these SLOs requires high-end GPUs, yet weight, cost, and power constraints preclude integrating such GPUs on-
robot. Prior works offload VLA inference to edge servers that serve many
robots on VLA models. However, current VLA systems lack support for multi-request, multi-model execution on a multi-GPU server under SLOs, while existing serving systems for multi-stage models are optimized for throughput and stage disaggregation across separate GPUs, which are ill-suited for the millisecond-scale stages of VLA models. We design Robion, the first VLA serving and management system for multi-
robot, multi-model requests on multi-GPU edge servers that meets SLOs. Our serving engine disaggregates the VLM and ADiT stages within a GPU via two streams, dynamically restricting the SMs on VLM stream so ADiT always finds SMs to run alongside it, and co-locates multiple models by sharing these streams across them, prioritizing requests by least remaining SLO time. Our management engine enables flexible model placements on multi-GPU servers, and integrates an intelligent traffic controller that maximizes per-model batching under the chosen placement while bounding each GPU's load to meet SLOs. For individual models, Robion serves on average 6.7$\times$ and 1.5$\times$ higher
robot load within 98% SLO attainment over vLLM-Omni, the most widely used multi-stage serving system, and Monolithic, which runs VLM and ADiT as a single pipeline, respectively. In a large-scale experiment of serving 8 different models on a 4-GPU server, Robion can serve up to 64
robots within 98% SLO attainment.
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All authors Dionysios Adamopoulos, Nattapol Chanpaisit, Basel Fakhri, Christina Giannoula
Distributed Computing
GPU-CFR: 80x Faster Counterfactual Regret Minimization by Compiling the Game to Static Dataflow and CUDA Graph Replay
Boning Li and Longbo Huang
Counterfactual regret minimization (CFR) is one of the few large numerical workloads that still runs faster on CPUs than on GPUs. Each iteration sweeps a game tree with up to billions of states in millions of small, interdependent gather and scatter steps issued through a generic tree interface. On a GPU every kernel finishes in microseconds, so kernel launches and framework dispatch dominate the run time, and prior GPU implementations have lost to optimized CPU code. We observe that for a fixed game, everything about a CFR iteration except the numerical values is known before the first iteration runs. We propose GPU-CFR, a compiler and runtime built on this observation. It compiles any game once into static dataflow: flat edge and information-set arrays, precomputed indices, and depth-level batched passes fix the entire operation sequence, and only solver state changes between iterations. Static chance folding, depth-level execution blocks, and a dual-lane reach buffer cut the number of framework operations by up to 18.1x. Because shapes, indices, and buffer addresses never change, CUDA Graph Replay records the iteration once and replays it with a single graph launch. On one A100, across an eight-game suite that spans card games, dice games, and board games, GPU-CFR runs 29.8–80.4x faster than the fastest prior GPU CFR on the same accelerator, and 14–258x faster than LiteEFG, one of the fastest open-source CPU implementations, on the four largest games. The compiled representation carries most of that margin: on eight CPU threads with no accelerator it is already 2.2–51.1x faster than the GPU baseline. On the CPU the optimized path reproduces the reference iterates bitwise, and tree construction and graph capture pay for themselves within the first solve. GPU-CFR beats every CPU and GPU baseline on the mid-to-large games of the suite without changing the update rule.
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Distributed Computing
Building py-kvcache: A Performance Characterization of External KV Caching for vLLM with NVMe SSDs
Joseph Kanichai, Tiziano De Matteis and Animesh Trivedi
Prefix caching can reduce the time to first
token (TTFT) of long-context LLM requests by reusing previously computed key-value (KV) states, but for short prefixes or fast GPUs, recomputation can be faster than loading from an external cache. We characterize this tradeoff in vLLM across GPU, CPU, and NVMe tiers using synthetic workloads, long-context
benchmarks, production traces, and find that cache performance depends on transfer granularity, intermediate
memory use, and when transfers enter the request schedule, not only on device bandwidth. These findings motivate py-kvcache, a vLLM KV Offload connector with asynchronous direct I/O, bounded shared staging, and scheduler-aware preloading, which starts disk reads while requests are still waiting, overlapping with compute. At 80k
tokens, py-kvcache loading from disk is 2.0x faster than LMCache, with preloading contributing 1.34x. With GPU, CPU, and disk caching enabled, it is 1.23x faster than LMCache and within approximately 4% of the native vLLM KV Offload implementation. LongBench and SCBench show that these benefits extend to irregular prefix chains and multi-turn workloads. Bailian trace replays improve TTFT on a weaker GPU, but on an H100 the average request falls below the break-even point and GPU
memory alone retains enough prefixes. External KV caching should therefore be treated as a setup specific admission decision. The py-kvcacheimplementation is available at: https://github.com/atlarge-research/py-kvcache.
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Distributed Computing
Entwine: Coordinating Tiled Computation and Fine-Grained Communication across GPUs
Kai Ma, Quanfeng Lv, Jingguo Ge et al. (+2 more)
Modern high-performance GPU computations partition tensors into tiles to exploit data reuse and parallelism. Individual tile computations complete earlier than the full tensor computation, creating opportunities to overlap computation and communication. However, a mismatch between computation and communication progress can limit these opportunities. Communication stalls when no data is ready, and may lag when data arrives in bursts. Communication can also slow computation by consuming shared resources, offsetting the benefits of overlap. We present Entwine, which coordinates tile computation order, fine-grained communication, and SM resource allocation to minimize overall completion time. Entwine reorders tile computation to produce data for communication at a more regular pace. Entwine couples this schedule with fine-grained SM-based communication to process tile results with low latency and low overhead. Since the communication kernel also consumes SM resources, Entwine coordinates their allocation to balance communication progress against computation slowdown. Across representative tensor-parallel LLM workloads, Entwine achieves a geomean speedup of 1.232x (up to 1.433x) over cuBLAS+NCCL, and outperforms state-of-the-art overlap baselines by 3.1-9.8% in geomean. We will open-source our implementation upon publication.
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All authors Kai Ma, Quanfeng Lv, Jingguo Ge, Bowei Dai, Kefan Ruan
Distributed Computing
Taming Bitwise Behavior in GPU Kernels with Tensor Core: Black-Box Reconstruction, Compiler Enforcement, and Static Verification
Ziteng Yang, Nicholas J. Riasanovsky, Warren Deng et al. (+1 more)
Determinism and numerical reproducibility are increasingly required of GPU kernels in machine learning systems, yet deterministic implementations of the same kernel can still differ bit for bit. Floating-point reduction order is the primary cause, alongside partial-sum precision, fused multiply-add operations, and rounding placement. These choices may be hand-coded, selected by a block-level
language such as Triton, or hidden inside a closed-source library such as cuBLAS or rocBLAS. A tile shape chosen for performance therefore also determines the arithmetic, potentially breaking batch invariance. Preserving a fixed order can cost up to 20 percent, while an autotuner cannot identify which configurations are bitwise equivalent. We characterize the factors determining the bitwise behavior of reductions and general
matrix multiplication (GEMM). First, we introduce a descriptor of GEMM reduction order, including the partitioning of K in split-K GEMM. Using it, we perform the first black-box reconstruction of a closed-source library's arithmetic for bit-level correctness. Our family of Triton GEMMs matches NVIDIA cuBLAS in all tested cases on Blackwell and Hopper. For realistic LLM shapes with fused epilogues, it matches or exceeds torch.compile performance. Second, we enforce balanced-tree reduction during Triton lowering and introduce a data-layout optimization that brings 19 of 27 kernels on GB300 and H100 within 10 percent of free-order performance. Third, we develop sound static checkers for bitwise equivalence between compiled GPU kernels, including the first checker spanning NVIDIA PTX and AMD GCN. Integrated into Triton's autotuner, the checker restricts search to a single bit-equivalence class.
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All authors Ziteng Yang, Nicholas J. Riasanovsky, Warren Deng, Vivek Sarkar
Distributed Computing
Rethinking Sparse Formats for RISC-V: A Hierarchical Approach to High-Performance SpMV
Anna Pirova, Anastasia Vodeneeva, Konstantin Kovalev et al. (+7 more)
The sparse
matrix-vector multiplication (SpMV)
algorithm is a fundamental computational kernel of linear
algebra and serves as a building block for numerous applications, primarily iterative solvers for systems of linear equations used in scientific and engineering simulations. This paper compares vectorized implementations of the SpMV
algorithm across eight established sparse
matrix storage formats and proposes a novel modification of the CSR format, Hierarchical CSR (HCSR), which enhances SpMV performance on RISC-V processors. Our SpMV implementations utilize RVV 1.0 intrinsics and are publicly available as an open-source C++ library named RVVLASparse. Computational experiments conducted on SpacemiT K1 and K3 RISC-V boards demonstrate that the proposed HCSR format achieves the shortest execution time among all considered formats across a broad class of sparse
matrices. HCSR outperforms the best CSR implementation on 8 cores, yielding an average speedup for double precision of 19% on K1 (13% on K3) and for single precision of 36% on K1 (34% on K3).
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All authors Anna Pirova, Anastasia Vodeneeva, Konstantin Kovalev, Alexander Ustinov, Maksim Zagriadskov, Daniil Litvyakov, Arthur Kulik, Evgeny Kozinov, Valentin Volokitin, Iosif Meyerov
Distributed Computing
Can AI Remediate Backend Failures Safely? GuardedAct with Blast-Radius-Aware Sandboxing
Wanrong Cai, Tianyu Yu, Shaorui Pi et al. (+2 more)
Large
Language Models (LLMs) have shown promising capabilities in generating remediation actions for microservice failures. However, directly executing AI-generated repair actions in production risks cascading collateral damage. We propose GuardedAct, a sandbox-first remediation framework that interposes a blast-radius-aware verification layer between the LLM action generator and the production environment. GuardedAct operates in four phases: (1) ingesting a diagnosis report together with the live system
topology and recent telemetry, (2) prompting an LLM to produce a ranked list of candidate remediation actions, (3) simulating each action in a lightweight digital-twin sandbox that estimates the blast radius and assigns a risk label, and (4) enforcing a rollback-confidence gate that auto-executes only low-risk actions while escalating high-risk ones for human review. We evaluate GuardedAct on five fault scenarios injected into the DeathStarBench social-network application. Experimental results show that GuardedAct achieves an overall recovery rate of 87.4% while reducing collateral damage by 79.7% relative to direct LLM execution (from 25.6% to 5.2%), at the cost of a modest sandbox-induced increase in mean time to recovery (approximately 8 s). Ablation studies confirm that each component contributes meaningfully to the safety-speed trade-off.
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All authors Wanrong Cai, Tianyu Yu, Shaorui Pi, Xiaoxuan Sun, Wenrui Ma
Distributed Computing · Cross-listed from cs.CR
A BUD You Can Count On: Efficient, Verifiable Membership Proofs
Alejandro Ranchal-Pedrosa, Cody Littley and Ben Marsh
A block typically changes only a small fraction of blockchain state, yet producing a state root makes validators update an authenticated tree spanning it all. We show how to support verifiable reads from the writes alone. We introduce Block Update Digests (BUDs), that commit to a block's writes and link each key touched in that block to its previous modification. An optional prior-value record lets one successor BUD authenticate the value between modifications, replacing the baseline's two BUD openings. SuperBUDs summarize those writes over longer intervals, letting a reader verify that a value remained unchanged without checking every intervening block. Thanks to BUDs and SuperBUDs, validators can just keep ordinary flat state while still serving proofs of current and historical values, including deletion. We prove soundness and completeness for reads at or after a key's first logged modification when the required proof data is available. In experiments with the baseline format, a 50x increase in state size raises the measured base-BUD cost by just 1.24x. In paired QMDB experiments, lowering its garbage-collection activation threshold raises process CPU time by 1.3-2.7x and device bytes written by 1.6-2.4x relative to its dormant configuration. BUD authentication requires no corresponding relocation of live entries. In the evaluated baseline, two-digest read-layer payloads stay below 800 bytes, and warm hash-path verification takes at most 146 {\mu}s at p99. Authenticated reads need not make validators maintain an authenticated tree over the entire state.
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Distributed Computing
The Computing Channel: How Modulation Programs the Airwaves
Saeed Razavikia and Carlo Fischione
Distributed computing and distributed artificial intelligence require frequent exchanges of intermediate results, although many applications need only an aggregate rather than messages from individual devices. Conventional systems recover each message before computing the aggregate, whereas over-the-air computation (OAC) exploits simultaneous transmission to obtain it directly. However, dominant OAC implementations rely on analog signaling, creating a mismatch with finite-precision data and digital communication procedures. This article presents digital function-oriented communication, in which finite-alphabet symbol representations and receiver decisions are jointly designed so that multiple-access superposition encodes the desired function without recovering individual inputs. We introduce its computational-constellation principle, main design approaches, extensions, and implementation challenges.
Federated edge learning illustrates how the framework can reduce user-dependent data-bearing resources while operating directly on quantized model updates.
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Distributed Computing · Cross-listed from cs.LG
Phase-Decoupled, Model-Calibrated Power Control for Disaggregated LLM Serving
Jae Gon Kim, Donghoon Yoo, Hanyul Ryu et al. (+3 more)
Datacenter GPU power is the binding constraint on LLM serving capacity, and production serving has shifted to prefill/decode (PD) disaggregation. Deploying NVIDIA's Max-Q inference profile on a disaggregated B200 system, we found its realized gain modest (+8.6%
tokens/J), model-dependent, and carrying a mean end-to-end latency cost (+5.2%) that throughput-only evaluation does not surface; the profile also applies one setting to prefill and decode GPUs that operate in opposite hardware regimes. We hypothesize that the optimal power setting is a property of the deployed (model, quantization, engine, hardware) combination rather than of the GPU class, that each lane warrants its own profile, and that converting SLO headroom into energy safely requires latency-gated calibration under a runtime SLO guard rather than a fixed recipe. We present a phase-decoupled, model-calibrated controller: the prefill lane runs under an SM-clock window whose floor is a latency guarantee by construction, and the decode lane under a power cap placed by automatic calibration just above a measured throughput/latency cliff. Because a disaggregated decode lane draws flat,
memory-bound power, the cap binds continuously, the reactive-overshoot weakness that led POLCA to reject capping is absent, and the GPU's own power manager retains throughput under the cap. On an 8x B200 node serving Qwen3-Coder-480B (FP8) under agentic load, our balanced mode delivers +20.4%
tokens/J at +3.5% mean e2e versus +8.6% at +5.2% for Max-Q, a Pareto improvement on both axes. On Qwen3-235B-A22B (NVFP4) every operating mode meets the ITL-p99 SLO in every repetition; both vendor profiles miss it. A decode-actuator A/B shows the calibrated cap beats static clock locks, and a three-day sustained run saves 32.3% of a lane pair's electricity. Both models are MoE; a dense model recovers roughly 5x less, so we scope our claims to MoE serving.
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All authors Jae Gon Kim, Donghoon Yoo, Hanyul Ryu, Sungho Ha, Juyeon Lee, Soojung Ryu
Distributed Computing · Cross-listed from cs.SE
A Model-Centric DevOps Architecture for DEVS-Based Digital Twin Simulation Services
Arnis Lektauers, Gusts Linkevičs, Guntis Mosāns et al. (+2 more)
Digital twin simulation models evolve and are redeployed like software. Engines based on the Discrete Event System Specification (DEVS) have a sound formal basis but offer little support for versioning, automated validation, or continuous delivery in cloud-native environments. This paper proposes a model-centric DevOps architecture that deploys DEVS-based digital twin simulations as managed services. Models are first-class DevOps artefacts written in a declarative
language based on YAML (YAML Ain't Markup
Language) with a tuple-level mapping to the multiPDEVS formalism. Repository continuous integration (CI) validates publishing manifests, the engine loader performs syntactic, structural, and static semantic checks before every simulation, and published model artefacts are versioned and immutable, so that an earlier validated version can be selected by pinning its identifier. The platform runs as containerised microservices on Kubernetes with engine adaptations that externalise inputs and results and expose lifecycle control. An initial case study on bus route 22 in Riga exercises the lifecycle on an offline model with roughly 115,000 DEVS atomic components and reports single-container throughput and concurrent job execution on one Kubernetes node. Behavioural validation and multi-node evaluation remain future work.
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All authors Arnis Lektauers, Gusts Linkevičs, Guntis Mosāns, Arina Fokina, Rasa Gulbe
Distributed Computing · Cross-listed from cs.LG
EMMI: Edge Multi-Modal Intelligence for Communication-Efficient MLLM Inference via Fused Representation Compression
Motahare Mounesan and Irfan Khan
Recent advances in
multimodal large
language mod- els (MLLMs) have opened new opportunities for edge intelligence by enabling
reasoning across heterogeneous sensor modalities, such as
vision, text, and telemetry data. However, deploying these capabilities on resource-constrained edge platforms remains challenging due to the substantial computational,
memory, and communication demands of modern MLLMs. Rather than transmitting raw sensor observations or partitioning neural networks at intermediate layers, Edge Multi-Modal Intelligence (EMMI) communicates a compact representation between edge devices and server resources, enabling communication-efficient edge MLLM inference. To achieve this, EMMI performs modality-specific encoding, cross-modal representation fusion, and learned compression at the edge, transmitting only a compact latent representation to server-side resources for high-capacity MLLM
reasoning. This representation-centric design reduces communication overhead, preserves local data
privacy, and provides a fixed-size interface between heterogeneous edge devices and server-side MLLMs. Evaluation on a representative
multimodal benchmark demonstrates that EMMI can reduce the communication payload by 32x while maintaining comparable downstream accuracy, resulting in up to a 3.4x reduction in estimated end-to-end inference latency under bandwidth-constrained edge conditions.
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Distributed Computing
Online Treasure Hunt in Vertex-Permuted Dynamic Rings
Kamran Ayoubi, Bernard Mans and Lata Narayanan
We study the problem of treasure hunt by a group of $k \geq 1$
agents in vertex-permuted dynamic rings (VP). In this model, the $n$ vertices remain on a ring but are permuted at each time step. We first show that treasure hunt is impossible for any $k \leq n-3$
agents, if there are no restrictions on the sequence of permutations used in the dynamic ring. We then study the $VP(\delta)$ setting, in which for every pair $i, j$ of vertices, the edge $(i, j)$ is guaranteed to appear within $\delta$ steps. We show that the class $VP(\delta)$ is feasible only for $\delta \geq \left\lceil \frac{n-1}{2}\right\rceil$. For the one-
agent case, we show a tight bound of $\Theta(\delta n)$ on the worst-case search time as well as competitive ratio of any online
algorithm for treasure hunt, provided $\delta \geq 2n$. We then give an optimal
algorithm for $k$
agents, thereby showing that $k$
agents can obtain a speedup of $k$ on the worst-case search time. Finally, in the R-VP setting, in which in every step, the vertices are arranged as a ring according to a random permutation, we show that treasure hunt takes expected $\Theta(n)$ steps against an oblivious adversary and $\Theta(n \log n)$ steps against an adaptive adversary.
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