arXiv subjects

Susmit Sarkar

Publications and source records attributed to Susmit Sarkar.

3 recordsLinked to original sources

arXiv2026

Quantized Stochastic Primal-Dual Methods for Distributed Optimization under Relaxed Global Geometry

We study distributed optimization with stochastic gradients and finite-bit communication modeled by random (unbiased) quantization. We propose q-PDGD, a quantized stochastic primal-dual method, and analyze it under relaxed global geometry. Under restricted secant inequality (RSI), a constant step-size yields linear contraction to an explicit neighborhood determined by gradient noise, quantization distortion, and network connectivity, while a diminishing step-size achieves O(1/k) convergence without shared-minimizer assumptions. Under Polyak-Lojasiewicz (PL) inequality, we obtain linear-to-neighborhood convergence in the same stochastic quantized setting. Our results match the best-known centralized stochastic rates in oracle complexity, and are supported by experiments demonstrating the predicted tradeoffs between quantization level, step-size choice, and graph structure.

math.OC↗

arXiv2018

Memory Consistency Models using Constraints

Memory consistency models (MCMs) are at the heart of concurrent programming. They represent the behaviour of concurrent programs at the chip level. To test these models small program snippets called litmus test are generated, which show allowed or forbidden behaviour of different MCMs. This paper is showcasing the use of constraint programming to automate the generation and testing of litmus tests for memory consistency models. We produce a few exemplary case studies for two MCMs, namely Sequential Consistency and Total Store Order. These studies demonstrate the flexibility of constrains programming in this context and lay foundation to the direct verification of MCMs against the software facing cache coherence protocols.

cs.PL↗

arXiv2017

Verification of a lazy cache coherence protocol against a weak memory model

In this paper we verify a modern lazy cache coherence protocol, TSO-CC, against the memory consistency model it was designed for, TSO. We achieve this by first showing a weak simulation relation between TSO-CC (with a fixed number of processors) and a novel finite-state operational model which exhibits the laziness of TSO-CC and satisfies TSO. We then extend this by an existing parameterisation technique, allowing verification for an unlimited number of processors. The approach is executed entirely within a model checker, no external tool is required and very little in-depth knowledge of formal verification methods is required of the verifier.

cs.LO↗