arXiv subjects

Rohit Chawla

Publications and source records attributed to Rohit Chawla.

7 recordsLinked to original sources

arXiv2025

MoE-Beyond: Learning-Based Expert Activation Prediction on Edge Devices

The deployment of large-scale Mixture-of-Experts (MoE) models on edge devices presents significant challenges due to memory constraints. While MoE architectures enable efficient utilization of computational resources by activating only a subset of experts per inference, they require careful memory management to operate efficiently in resource-constrained environments. Traditional heuristic-based expert caching strategies such as MoE-Infinity struggle to maintain high cache hit rates as models parameters scale. In this work, we introduce MoE-Beyond, a learning-based expert activation predictor trained to predict expert activations during autoregressive decoding. By framing the task as a multi-label sequence prediction problem, we train a lightweight transformer model on 66 million expert activation traces extracted from LDJnr-Puffin dataset [5] using DeepSeek-V2-Chat-Lite MoE. Our predictor generalizes effectively across unseen prompts from WebGLM-QA dataset [6], achieving 97.5% accuracy and an 86.6% F1-score. Simulation results show that MoE-Beyond improves GPU cache hit rate from 17% to 72% when only 10% of experts fit in GPU cache, outperforming heuristic baselines.

cs.LG↗

arXiv2025

Higher-Order Transverse Discontinuity Mapping in Filippov Systems: Analysis and Experimental Validation using an Electronic Circuit

This paper shows that linearizing the transverse discontinuity mapping (TDM) in Filippov systems can produce inaccurate predictions of the dynamics in impact oscillators operating near a pre-stressed soft barrier. This discrepancy arises from the limitations of the linearized saltation matrix, which inaccurately predicts impacts in the local neighborhood of the discontinuity boundary. To address this issue, a higher-order approximation of the TDM is derived, which accurately captures the onset of impacts and closely matches the results obtained from both numerical simulations and electronic experiments. The proposed higher-order TDM results in a quadratic estimation of flight time for impacts. Geometrically, real-valued impact events are only feasible when the discriminant of this quadratic equation is positive. The differences in the predicted higher-order flight times and mapping estimates become more pronounced for low-velocity impacts close to grazing. Subsequently, a numerical approximation of the higher-order saltation matrix and its consequent Floquet multipliers and Lyapunov exponents for stability analysis is proposed and demonstrated on a pre-stressed, forced, damped, soft impact oscillator. To validate the numerically observed discontinuity-induced bifurcations, an analog electronic circuit is proposed that models a soft mechanical prestressed oscillator. This inductor-less circuit overcomes the limitations of typical LCR-based circuits, which are used to design such oscillators but cannot accommodate low stiffness ratios. The experimentally obtained limit cycles, finger-shaped Poincar\'e sections, and bifurcation diagrams match the predictions of the higher-order TDM, validating that the proposed circuit accurately models the soft-impact oscillator for both low and high stiffness ratios.

nlin.CD↗

arXiv2024

Wake-induced response of vibro-impacting systems

The stability and bifurcation behaviour of a wake-induced vibro-impacting oscillator is studied. The effects of a discontinuity on the stability of the structure while it is undergoing phase-locked motions due to the surrounding fluid-structure interactions (FSI) are examined. The primary structure and the near wake dynamics are modelled as a harmonic oscillator and a Van der Pol oscillator, respectively, and are weakly coupled to each other via acceleration coupling. Qualitative changes in the dynamical behaviour of this system are investigated in the context of discontinuity-induced bifurcations (DIBs) that result from the interaction of fluid flow and non-smoothness from the primary structure. Phenomenological behaviours like the co-existence of attractors and period-adding cascades of limit cycles separated by chaotic orbits are observed. The existence of these phenomena is demonstrated via stability analysis using Floquet theory and the associated Lyapunov spectra. In addition, the behaviour of orbits in the local neighbourhood of the barrier is defined using a higher-order transverse discontinuity map. This mapping is implemented to obtain the respective Lyapunov exponents. Solutions obtained using this modified algorithm are demonstrated to accurately predict both stable and chaotic regimes, as observed from the corresponding bifurcation diagrams.

nlin.CD↗

arXiv2022

Improved Stability Estimates and Flight Time Predictions Using Higher-Order Transverse Discontinuity Mapping in Hybrid Dynamical Systems

This article emphasizes on inconsistencies in the dynamical estimates obtained by first-order transverse discontinuity mapping (TDM) and direct numerical observations for hybrid dynamical systems. Pitfalls of locally linearizing hybrid nonlinear dynamical systems near discontinuity boundaries are demonstrated along with examples of how such linearization could lead to incorrect estimates of impact occurrences for transverse interactions with a rigid barrier. A higher-order TDM is proposed to overcome this shortcoming, allowing for better analytical estimation of impact occurrence times, state transitions, and, consequently, the evolution of trajectories. The difference in flight times of two closely initiated trajectories in the local neighbourhood of a discontinuity boundary is estimated up to $\mathcal{O}(2)$. The resulting quadratic equation implies that the orbits local to the impacting state, corresponding to a negative discriminant, won't reach the discontinuity boundary. Further, the $\mathcal{O}(2)$ correction terms to the analytical expression of the TDM ensure that the flight time estimates do not diverge for low-velocity impacts near grazing, thereby avoiding overestimation of the mapped state. A numerical method is subsequently developed to estimate a saltation matrix incorporating the proposed higher-order TDM to avoid incorrect impact occurrences. Modifications to the existing algorithms used to numerically quantify local stability, namely the Lyapunov spectra and Floquet multipliers, are proposed. Stability analyses using the proposed higher-order approach are carried out for representative cases of a hard impact oscillator and a pair impact oscillator, with results consistent with numerically obtained bifurcation diagrams.

nlin.CD↗

arXiv2019

Quantum fluctuations stabilize an inverted pendulum

We explore analytically the quantum dynamics of a point mass pendulum using the Heisenberg equation of motion. Choosing as variables the mean position of the pendulum, a suitably defined generalised variance and a generalised skewness, we set up a dynamical system which reproduces the correct limits of simple harmonic oscillator like and free rotor like behaviour. We then find the unexpected result that the quantum pendulum released from and near the inverted position executes oscillatory motion around the classically unstable position provided the initial wave packet has a variance much greater than the variance of the well known coherent state of the simple harmonic oscillator. The behaviour of the dynamical system for the quantum pendulum is a higher dimensional analogue of the behaviour of the Kapitza pendulum where the point of support is vibrated vertically with a frequency higher than the critical value needed to stabilize the inverted position. A somewhat similar phenomenon has recently been observed in the non equilibrium dynamics of a spin - 1 Bose-Einstein Condensate.

nlin.CD↗

arXiv2019

Quantum dynamics from fixed points and their stability

We approach quantum dynamics in one spatial dimension from a systematic study of moments starting from the dynamics of the mean position. This is complementary to the approach of Brizuela whose starting point was generalized recursion relations between moments. The infinite set of coupled equations is truncated which allows us to use the techniques used in the study of dynamical systems. In particular we predict for what initial variance the purely quartic oscillator will time develop with minimal change in the shape of the initial packet and what the frequency of oscillation of the mean position will be. We show how quantum fluctuations will cause a particle to escape from the well of a volcano potential and how they will cause an oscillation between the two wells of a double well potential. Further, we consider an oscillatory external field in addition to the double well potential and work near the separatrix where the classical system is known to be chaotic. We show how the quantum fluctuations suppresses the chaotic behaviour after a time interval inversely proportional to the strength of the quantum fluctuations.

quant-ph↗

arXiv2018

From periodically driven double wells to volcano potentials: Quantum dynamics

We consider the dynamics of a particle confined in a double well potential which is subjected to a periodic drive. In the case of deep and well separated wells, we find that by adjusting the parameters of the drive we can generate, to a very good approximation, a volcano potential. The quantum dynamics in this volcano potential is studied by a variation of what can be called a generalized Ehrenfest's theorem. We find that the coupling of the mean position and the width of the wave packet in this dynamics causes the particle to escape from the central well in accordance with the fact that the volcano potential only supports resonance states.

quant-ph↗