TAXI: Traveling Salesman Problem Accelerator with X-bar-based Ising Macros Powered by SOT-MRAMs and Hierarchical Clustering

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Main Authors: Yoo, Sangmin, Holla, Amod, Sanyal, Sourav, Kim, Dong Eun, Iacopi, Francesca, Biswas, Dwaipayan, Myers, James, Roy, Kaushik
Format: Preprint
Published: 2025
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author Yoo, Sangmin
Holla, Amod
Sanyal, Sourav
Kim, Dong Eun
Iacopi, Francesca
Biswas, Dwaipayan
Myers, James
Roy, Kaushik
author_facet Yoo, Sangmin
Holla, Amod
Sanyal, Sourav
Kim, Dong Eun
Iacopi, Francesca
Biswas, Dwaipayan
Myers, James
Roy, Kaushik
contents Ising solvers with hierarchical clustering have shown promise for large-scale Traveling Salesman Problems (TSPs), in terms of latency and energy. However, most of these methods still face unacceptable quality degradation as the problem size increases beyond a certain extent. Additionally, their hardware-agnostic adoptions limit their ability to fully exploit available hardware resources. In this work, we introduce TAXI -- an in-memory computing-based TSP accelerator with crossbar(Xbar)-based Ising macros. Each macro independently solves a TSP sub-problem, obtained by hierarchical clustering, without the need for any off-macro data movement, leading to massive parallelism. Within the macro, Spin-Orbit-Torque (SOT) devices serve as compact energy-efficient random number generators enabling rapid "natural annealing". By leveraging hardware-algorithm co-design, TAXI offers improvements in solution quality, speed, and energy-efficiency on TSPs up to 85,900 cities (the largest TSPLIB instance). TAXI produces solutions that are only 22% and 20% longer than the Concorde solver's exact solution on 33,810 and 85,900 city TSPs, respectively. TAXI outperforms a current state-of-the-art clustering-based Ising solver, being 8x faster on average across 20 benchmark problems from TSPLib.
format Preprint
id arxiv_https___arxiv_org_abs_2504_13294
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle TAXI: Traveling Salesman Problem Accelerator with X-bar-based Ising Macros Powered by SOT-MRAMs and Hierarchical Clustering
Yoo, Sangmin
Holla, Amod
Sanyal, Sourav
Kim, Dong Eun
Iacopi, Francesca
Biswas, Dwaipayan
Myers, James
Roy, Kaushik
Emerging Technologies
Ising solvers with hierarchical clustering have shown promise for large-scale Traveling Salesman Problems (TSPs), in terms of latency and energy. However, most of these methods still face unacceptable quality degradation as the problem size increases beyond a certain extent. Additionally, their hardware-agnostic adoptions limit their ability to fully exploit available hardware resources. In this work, we introduce TAXI -- an in-memory computing-based TSP accelerator with crossbar(Xbar)-based Ising macros. Each macro independently solves a TSP sub-problem, obtained by hierarchical clustering, without the need for any off-macro data movement, leading to massive parallelism. Within the macro, Spin-Orbit-Torque (SOT) devices serve as compact energy-efficient random number generators enabling rapid "natural annealing". By leveraging hardware-algorithm co-design, TAXI offers improvements in solution quality, speed, and energy-efficiency on TSPs up to 85,900 cities (the largest TSPLIB instance). TAXI produces solutions that are only 22% and 20% longer than the Concorde solver's exact solution on 33,810 and 85,900 city TSPs, respectively. TAXI outperforms a current state-of-the-art clustering-based Ising solver, being 8x faster on average across 20 benchmark problems from TSPLib.
title TAXI: Traveling Salesman Problem Accelerator with X-bar-based Ising Macros Powered by SOT-MRAMs and Hierarchical Clustering
topic Emerging Technologies
url https://arxiv.org/abs/2504.13294