5 Search Results for "Madan, Vivek"

Document
DOI: 10.4230/LIPIcs.SoCG.2026.48
FPT Approximations for Capacitated Sum of Radii and Diameters

Authors: Arnold Filtser and Ameet Gadekar

Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)

Abstract
The Capacitated Sum of Radii problem involves partitioning a set of points P, where each point p ∈ P has capacity U_p, into k clusters that minimize the sum of cluster radii, such that the number of points in the cluster centered at point p is at most U_p. We begin by showing that the problem is APX-hard, and that under gap-ETH there is no parameterized approximation scheme (FPT-AS). We then construct a ≈5.83-approximation algorithm in FPT time (improving a previous ≈7.61 approximation in FPT time). Our results also hold when the objective is a general monotone symmetric norm of radii. We also improve the approximation factors for the uniform capacity case, and for the closely related problem of Capacitated Sum of Diameters.
Cite as

Arnold Filtser and Ameet Gadekar. FPT Approximations for Capacitated Sum of Radii and Diameters. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 48:1-48:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{filtser_et_al:LIPIcs.SoCG.2026.48,
  author =	{Filtser, Arnold and Gadekar, Ameet},
  title =	{{FPT Approximations for Capacitated Sum of Radii and Diameters}},
  booktitle =	{42nd International Symposium on Computational Geometry (SoCG 2026)},
  pages =	{48:1--48:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-418-5},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{367},
  editor =	{Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.48},
  URN =		{urn:nbn:de:0030-drops-258545},
  doi =		{10.4230/LIPIcs.SoCG.2026.48},
  annote =	{Keywords: clustering, sum of radii, sum of diameter, capacitated clustering, fpt}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2025.21
GSOHC: Global Synchronization Optimization in Heterogeneous Computing

Authors: Soumik Kumar Basu and Jyothi Vedurada

Published in: LIPIcs, Volume 333, 39th European Conference on Object-Oriented Programming (ECOOP 2025)

Abstract
The use of heterogeneous systems has become widespread and popular in the past decade with more than one type of processor, such as CPUs, GPUs (Graphics Processing Units), and FPGAs (Field Programmable Gate Arrays) etc. A wide range of applications use both CPU and GPU to leverage the benefits of their unique features and strengths. Therefore, collaborative computation between CPU and GPU is essential to achieve high program performance. However, poorly placed global synchronization barriers and synchronous memory transfers are the main bottlenecks to enhanced program performance, preventing CPU and GPU computations from overlapping. Based on this observation, we propose a new optimization technique called hetero-sync motion that can relocate such barrier instructions to new locations, resulting in improved performance in CPU-GPU heterogeneous programs. Further, we propose GSOHC, a compiler analysis and optimization framework that automatically finds opportunities for hetero-sync motion in the input program and then performs code transformation to apply the optimization. Our static analysis is a context-sensitive, flow-sensitive inter-procedural data-flow analysis with three phases to identify the optimization opportunities precisely. We have implemented GSOHC using LLVM/Clang infrastructure. On A4000, P100 and A100 GPUs, our optimization achieves speedups of up to 1.8x, 1.9x and 1.9x over the baseline, respectively.
Cite as

Soumik Kumar Basu and Jyothi Vedurada. GSOHC: Global Synchronization Optimization in Heterogeneous Computing. In 39th European Conference on Object-Oriented Programming (ECOOP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 333, pp. 21:1-21:30, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{kumarbasu_et_al:LIPIcs.ECOOP.2025.21,
  author =	{Kumar Basu, Soumik and Vedurada, Jyothi},
  title =	{{GSOHC: Global Synchronization Optimization in Heterogeneous Computing}},
  booktitle =	{39th European Conference on Object-Oriented Programming (ECOOP 2025)},
  pages =	{21:1--21:30},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-373-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{333},
  editor =	{Aldrich, Jonathan and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2025.21},
  URN =		{urn:nbn:de:0030-drops-232949},
  doi =		{10.4230/LIPIcs.ECOOP.2025.21},
  annote =	{Keywords: Static Analysis, Synchronization, CPU-GPU, Heterogeneous Computing, Parallelization}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2025.23
Wastrumentation: Portable WebAssembly Dynamic Analysis with Support for Intercession

Authors: Aäron Munsters, Angel Luis Scull Pupo, and Elisa Gonzalez Boix

Published in: LIPIcs, Volume 333, 39th European Conference on Object-Oriented Programming (ECOOP 2025)

Abstract
Dynamic program analyses help in understanding a program’s runtime behavior and detect issues related to security, program comprehension, or profiling. Instrumentation platforms aid analysis developers by offering a high-level API to write the analysis, and inserting the analysis into the target program. However, current instrumentation platforms for WebAssembly (Wasm) restrict analysis portability because they require concrete runtime environments. Moreover, their analysis API only allows the development of analyses that observe the target program but cannot modify it. As a result, many popular dynamic analyses present for other languages, such as runtime hardening, virtual patching or runtime optimization, cannot currently be implemented for Wasm atop a dynamic analysis platform. Instead, they need to be built manually, which requires knowledge of low-level details of the Wasm’s semantics and instruction set, and how to safely manipulate it. This paper introduces Wastrumentation, the first dynamic analysis platform for WebAssembly that supports intercession. Our solution, based on source code instrumentation, weaves the analysis code directly into the target program code. Inlining the analysis into the target’s source code avoids dependencies on the runtime environment, making analyses portable across Wasm VMs. Moreover, it enables the implementation of analyses in any Wasm-compatible language. We evaluate our solution in two ways. First, we compare it against a state-of-the-art source code instrumentation platform using the WasmR3 benchmarks. The results show improved memory consumption and competitive performance overhead. Second, we develop an extensive portfolio of dynamic analyses, including novel analyses previously unattainable with source code instrumentation platforms, such as memoization, safe heap access, and the removal of NaN non-determinism.
Cite as

Aäron Munsters, Angel Luis Scull Pupo, and Elisa Gonzalez Boix. Wastrumentation: Portable WebAssembly Dynamic Analysis with Support for Intercession. In 39th European Conference on Object-Oriented Programming (ECOOP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 333, pp. 23:1-23:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{munsters_et_al:LIPIcs.ECOOP.2025.23,
  author =	{Munsters, A\"{a}ron and Scull Pupo, Angel Luis and Gonzalez Boix, Elisa},
  title =	{{Wastrumentation: Portable WebAssembly Dynamic Analysis with Support for Intercession}},
  booktitle =	{39th European Conference on Object-Oriented Programming (ECOOP 2025)},
  pages =	{23:1--23:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-373-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{333},
  editor =	{Aldrich, Jonathan and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2025.23},
  URN =		{urn:nbn:de:0030-drops-233153},
  doi =		{10.4230/LIPIcs.ECOOP.2025.23},
  annote =	{Keywords: WebAssembly, dynamic analysis, instrumentation platform, intercession}
}
Document
DOI: 10.4230/LIPIcs.ICALP.2018.84
Spectrally Robust Graph Isomorphism

Authors: Alexandra Kolla, Ioannis Koutis, Vivek Madan, and Ali Kemal Sinop

Published in: LIPIcs, Volume 107, 45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)

Abstract
We initiate the study of spectral generalizations of the graph isomorphism problem. b) The Spectral Graph Dominance (SGD) problem: On input of two graphs G and H does there exist a permutation pi such that G preceq pi(H)? c) The Spectrally Robust Graph Isomorphism (kappa-SRGI) problem: On input of two graphs G and H, find the smallest number kappa over all permutations pi such that pi(H) preceq G preceq kappa c pi(H) for some c. SRGI is a natural formulation of the network alignment problem that has various applications, most notably in computational biology. G preceq c H means that for all vectors x we have x^T L_G x <= c x^T L_H x, where L_G is the Laplacian G. We prove NP-hardness for SGD. We also present a kappa^3-approximation algorithm for SRGI for the case when both G and H are bounded-degree trees. The algorithm runs in polynomial time when kappa is a constant.
Cite as

Alexandra Kolla, Ioannis Koutis, Vivek Madan, and Ali Kemal Sinop. Spectrally Robust Graph Isomorphism. In 45th International Colloquium on Automata, Languages, and Programming (ICALP 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 107, pp. 84:1-84:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{kolla_et_al:LIPIcs.ICALP.2018.84,
  author =	{Kolla, Alexandra and Koutis, Ioannis and Madan, Vivek and Sinop, Ali Kemal},
  title =	{{Spectrally Robust Graph Isomorphism}},
  booktitle =	{45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)},
  pages =	{84:1--84:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-076-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{107},
  editor =	{Chatzigiannakis, Ioannis and Kaklamanis, Christos and Marx, D\'{a}niel and Sannella, Donald},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2018.84},
  URN =		{urn:nbn:de:0030-drops-90887},
  doi =		{10.4230/LIPIcs.ICALP.2018.84},
  annote =	{Keywords: Network Alignment, Graph Isomorphism, Graph Similarity}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2017.24
On the Expansion of Group-Based Lifts

Authors: Naman Agarwal, Karthekeyan Chandrasekaran, Alexandra Kolla, and Vivek Madan

Published in: LIPIcs, Volume 81, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017)

Abstract
A k-lift of an n-vertex base graph G is a graph H on nxk vertices, where each vertex v of G is replaced by k vertices v_1,...,v_k and each edge uv in G is replaced by a matching representing a bijection pi_{uv} so that the edges of H are of the form (u_i,v_{pi_{uv}(i)}). Lifts have been investigated as a means to efficiently construct expanders. In this work, we study lifts obtained from groups and group actions. We derive the spectrum of such lifts via the representation theory principles of the underlying group. Our main results are: 1. A uniform random lift by a cyclic group of order k of any n-vertex d-regular base graph G, with the nontrivial eigenvalues of the adjacency matrix of G bounded by lambda in magnitude, has the new nontrivial eigenvalues bounded by lambda+O(sqrt{d}) in magnitude with probability 1-ke^{-Omega(n/d^2)}. The probability bounds as well as the dependency on lambda are almost optimal. As a special case, we obtain that there is a constant c_1 such that for every k<=2^{c_1n/d^2}, there exists a lift H of every Ramanujan graph by a cyclic group of order k such that H is almost Ramanujan (nontrivial eigenvalues of the adjacency matrix at most O(sqrt{d}) in magnitude). We also show how this result leads to a quasi-polynomial time deterministic algorithm to construct almost Ramanujan expanders. 2. There is a constant c_2 such that for every k>=2^{c_2nd}, there does not exist an abelian k-lift H of any n-vertex d-regular base graph such that H is almost Ramanujan. This can be viewed as an analogue of the well-known no-expansion result for constant degree abelian Cayley graphs. Suppose k_0 is the order of the largest abelian group that produces expanding lifts. Our two results highlight lower and upper bounds on k_0 that are tight upto a factor of d^3 in the exponent, thus suggesting a threshold phenomenon.
Cite as

Naman Agarwal, Karthekeyan Chandrasekaran, Alexandra Kolla, and Vivek Madan. On the Expansion of Group-Based Lifts. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 81, pp. 24:1-24:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{agarwal_et_al:LIPIcs.APPROX-RANDOM.2017.24,
  author =	{Agarwal, Naman and Chandrasekaran, Karthekeyan and Kolla, Alexandra and Madan, Vivek},
  title =	{{On the Expansion of Group-Based Lifts}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017)},
  pages =	{24:1--24:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-044-6},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{81},
  editor =	{Jansen, Klaus and Rolim, Jos\'{e} D. P. and Williamson, David P. and Vempala, Santosh S.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2017.24},
  URN =		{urn:nbn:de:0030-drops-75739},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2017.24},
  annote =	{Keywords: Expanders, Lifts, Spectral Graph Theory}
}
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