arXiv subjects

Sie Hendrata Dharmawan

Publications and source records attributed to Sie Hendrata Dharmawan.

4 recordsLinked to original sources

arXiv2026

Sphere of Influence Centrality via Shapley Values: Empirical Approximation and Network Coverage Analysis

Node centrality is a fundamental problem in network analysis, yet classical metrics fail to capture the collective, coalitional nature of influence. We present a systematic empirical evaluation of the Shapley-value-based framework for the sphere of influence problem -- selecting $m$ nodes to maximize network coverage under three reachability criteria: single-hop, $k$-hop, and multi-path connectivity -- using exact polynomial-time algorithms due to Michalak et al. Evaluation across three diverse real-world networks (Euroroad, Facebook TV Shows, and Cora) demonstrates that practical approximation ratios consistently approach 0.9, substantially exceeding the theoretical $(1-1/e)$ lower bound, and that the Shapley-based approach dramatically outperforms a degree-based baseline, particularly in hub-and-spoke topologies. In the most striking case, Shapley-based selection identifies just 26 nodes (under 1\% of the Cora network) sufficient to influence half the graph under 3-hop reachability, compared to substantially larger sets required by the naive baseline.

cs.SI↗

arXiv2026

SBM With Multiple Samples: Improved Spectral Recovery

We study community detection in the two-block stochastic block model under the setting where multiple independent graph samples drawn from the same distribution are available. Building on a recently simplified spectral algorithm that preserves the independence of adjacency matrix entries throughout, we show that averaging $m$ independent samples before applying spectral partitioning reduces the error bound $\gamma$ exponentially in $m$: specifically, one can find a $\gamma$-correct partition with probability $1 - o(1)$ whenever $\frac{(a-b)^2}{a+b} \geq \frac{C}{m} \log \frac{2}{\gamma}$, improving the single-sample requirement by a factor of $m$. The key technical contribution is a multi-sample analogue of the spectral norm bound on the noise matrix, which propagates through the Davis-Kahan subspace angle analysis to yield the improved recovery guarantee. We provide experimental validation across a range of graph sizes ($n$ up to $1000$) and sample counts ($m$ up to $9$), demonstrating that the derived bounds are sharp and that even two or three samples yield dramatic improvements in recovery accuracy. Our results offer a rigorous theoretical foundation for graph data augmentation strategies used in modern graph representation learning.

cs.SI↗

arXiv2026

Simplify to Amplify: Achieving Information-Theoretic Bounds with Fewer Steps in Spectral Community Detection

We propose a streamlined spectral algorithm for community detection in the two-community stochastic block model (SBM) under constant edge density assumptions. By reducing algorithmic complexity through the elimination of non-essential preprocessing steps, our method directly leverages the spectral properties of the adjacency matrix. We demonstrate that our algorithm exploits specific characteristics of the second eigenvector to achieve improved error bounds that approach information-theoretic limits, representing a significant improvement over existing methods. Theoretical analysis establishes that our error rates are tighter than previously reported bounds in the literature. Comprehensive experimental validation confirms our theoretical findings and demonstrates the practical effectiveness of the simplified approach. Our results suggest that algorithmic simplification, rather than increasing complexity, can lead to both computational efficiency and enhanced performance in spectral community detection.

cs.SI↗

arXiv2025

PoolFlip: A Multi-Agent Reinforcement Learning Security Environment for Cyber Defense

Cyber defense requires automating defensive decision-making under stealthy, deceptive, and continuously evolving adversarial strategies. The FlipIt game provides a foundational framework for modeling interactions between a defender and an advanced adversary that compromises a system without being immediately detected. In FlipIt, the attacker and defender compete to control a shared resource by performing a Flip action and paying a cost. However, the existing FlipIt frameworks rely on a small number of heuristics or specialized learning techniques, which can lead to brittleness and the inability to adapt to new attacks. To address these limitations, we introduce PoolFlip, a multi-agent gym environment that extends the FlipIt game to allow efficient learning for attackers and defenders. Furthermore, we propose Flip-PSRO, a multi-agent reinforcement learning (MARL) approach that leverages population-based training to train defender agents equipped to generalize against a range of unknown, potentially adaptive opponents. Our empirical results suggest that Flip-PSRO defenders are $2\times$ more effective than baselines to generalize to a heuristic attack not exposed in training. In addition, our newly designed ownership-based utility functions ensure that Flip-PSRO defenders maintain a high level of control while optimizing performance.

cs.LG↗