arXiv subjects

D. Balamurugan

Publications and source records attributed to D. Balamurugan.

5 recordsLinked to original sources

arXiv2026

OmniPilot: An Uncertainty-Aware LLM Inference Advisor for Heterogeneous GPU Clusters

Serving large language models (LLMs) on a shared, heterogeneous GPU cluster requires users and operators to select the GPU type, tensor-parallel degree, and precision before committing valuable node-hours. Making these choices is challenging because effective throughput, launch-success rates, and cluster demand and utilization continuously fluctuate. Furthermore, static configuration recipes miss critical interactions: quantization effects depend heavily on the model family, key-value cache pressure creates size-by-precision trade-offs, and failure rates vary by more than twofold across different tensor-parallel degrees. Additionally, cluster resources are frequently constrained by unpredictable hardware failures. To address these challenges, we present \textbf{OmniPilot}, a launch advisor that predicts serving costs for feasible configurations and abstains when requests fall outside its measured support envelope. OmniPilot pairs a conformally calibrated quantile cost model (spanning eight serving targets) with an out-of-distribution (OOD) abstention layer. It ranks configurations using an economic utility metric calibrated to an operator's revealed preferences. In evaluations across 460 benchmark runs on A100, H100, and H200 hardware across four precisions, OmniPilot predicts aggregate throughput with a 6.2\% mean absolute percentage error (MAPE) and a log-space $R^2=0.92$. The advisor achieves 95\% top-1 accuracy with a mean utility regret of just 0.003. When tested on an OOD holdout of unsupported cells, prediction error climbs to 24-46\% and conformal intervals cover 0 of 5 points; however, the abstention layer successfully flags all five as low-confidence. Over time, these OOD scenarios will be integrated into the training dataset to continuously expand the advisor's support envelope.

cs.DC↗

arXiv2011

Multiscale Simulation of Quantum Nanosystems: Plasmonics of Silver Particles

Quantum nanosystems involve the coupled dynamics of fermions or bosons across multiple scales in space and time. Examples include quantum dots, superconducting or magnetic nanoparticles, molecular wires, and graphene nanoribbons. The number (10^3 to 10^9) of electrons in assemblies of interest here presents a challenge for traditional quantum computations. However, results from deductive multiscale analysis yield coarse-grained wave equation that capture the longer-scale quantum dynamics of these systems; a companion short-scale equation is also developed that allows for the construction of effective masses and interactions involved in the coarse-grained wave equation. The theory suggest an efficient algorithm for simulating quantum nanosystem which is implemented here. A variational Monte Carlo method is used to simulate the co-evolution of long- and short-scale processes. The approach does not require experimental data for calibration. It is validated via experimental data and TDDFT predictions on the nanoparticle size dependence of the plasmon spectrum.

cond-mat.mes-hall↗

arXiv2006

Charge-induced effects on the structure and properties of silane and disilane derivatives

Using ab-initio electronic structure methods we have investigated the ground state structures and properties of neutral and charged SiH$_{m}$(m=1-4) and Si$_{2}$H$_{n}$(n=1-6) clusters which are produced in the plasma enhanced chemical vapor deposition process used in the preparation of hydrogenated amorphous silicon({\it{a}}-Si:H). Our results show that charging a neutral cluster distorts it and the distortion mainly occurs through the orientation of Si-H bond. We attribute structural changes in the charged clusters to electrostatic repulsion between the bonded and non-bonded electrons. We find that in addition to the usual Si-H bond, hydrogen atoms form Si-H-H and Si-H-Si bonds in some clusters. The vibrations of Si-H, Si-Si, Si-H-Si bond stretching modes show that the frequencies are shifted significantly upon charging. The frequency shifts in the charged clusters are consistent with their bond length variations. We discuss the fragmentation pathways of silane into binary products and the role of fragmented silane radicals in the cluster formation and {\it{a}}-Si:H film deposition process.

cond-mat.mtrl-sci↗

arXiv2005

Effect of Nuclear Quadrupole Interaction on the Relaxation in Amorphous Solids

Recently it has been experimentally demonstrated that certain glasses display an unexpected magnetic field dependence of the dielectric constant. In particular, the echo technique experiments have shown that the echo amplitude depends on the magnetic field. The analysis of these experiments results in the conclusion that the effect seems to be related to the nuclear degrees of freedom of tunneling systems. The interactions of a nuclear quadrupole electrical moment with the crystal field and of a nuclear magnetic moment with magnetic field transform the two-level tunneling systems inherent in amorphous dielectrics into many-level tunneling systems. The fact that these features show up at temperatures $T<100mK$, where the properties of amorphous materials are governed by the long-range $R^{-3}$ interaction between tunneling systems, suggests that this interaction is responsible for the magnetic field dependent relaxation. We have developed a theory of many-body relaxation in an ensemble of interacting many-level tunneling systems and show that the relaxation rate is controlled by the magnetic field. The results obtained correlate with the available experimental data. Our approach strongly supports the idea that the nuclear quadrupole interaction is just the key for understanding the unusual behavior of glasses in a magnetic field.

cond-mat.dis-nn↗

arXiv2001

Effect of hydrogen on ground state structures of small silicon clusters

We present results for ground state structures of small Si$_{n}$H (2 \leq \emph{n} \leq 10) clusters using the Car-Parrinello molecular dynamics. In particular, we focus on how the addition of a hydrogen atom affects the ground state geometry, total energy and the first excited electronic level gap of an Si$_{n}$ cluster. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen bonds with two silicon atoms only in Si$_{2}$H, Si$_{3}$H and Si$_{5}$H clusters, while in other clusters (i.e. Si$_{4}$H, Si$_{6}$H, Si$_{7}$H, Si$_{8}$H, Si$_{9}$H and Si$_{10}$H) hydrogen is bonded to only one silicon atom. Also in the case of a compact and closed silicon cluster hydrogen bonds to the cluster from outside. We find that the first excited electronic level gap of Si$_{n}$ and Si$_{n}$H fluctuates as a function of size and this may provide a first principles basis for the short-range potential fluctuations in hydrogenated amorphous silicon. Our results show that the addition of a single hydrogen can cause large changes in the electronic structure of a silicon cluster, though the geometry is not much affected. Our calculation of the lowest energy fragmentation products of Si$_{n}$H clusters shows that hydrogen is easily removed from Si$_{n}$H clusters.

cond-mat.mtrl-sci↗