# Lock-Free Transactional Adjacency List

## TL;DR

This paper introduces a lock-free transactional adjacency list using an MDList structure, enabling efficient, atomic graph operations with significant performance improvements over existing methods.

## Contribution

It presents a novel lock-free transactional adjacency list based on MDList, combining linked list strategies with transactional capabilities for high-performance graph data management.

## Key findings

- Achieves 50% speedup over transactional boosting implementations
- Efficiently organizes graph vertices and edges in a lock-free manner
- Ensures linearizability and transactional correctness

## Abstract

Adjacency lists are frequently used in graphing or map based applications. Although efficient concurrent linked-list algorithms are well known, it can be difficult to adapt these approaches to build a high-performance adjacency list. Furthermore, it can often be desirable to execute operations in these data structures transactionally, or perform a sequence of operations in one atomic step. In this paper, we present a lock-free transactional adjacency list based on a multi-dimensional list (MDList). We are able to combine known linked list strategies with the capability of the MDList in order to efficiently organize graph vertexes and their edges. We design our underlying data structure to be node-based and linearizable, then use the Lock-Free Transactional Transformation (LFTT) methodology to efficiently enable transactional execution. In our performance evaluation, our lock-free transactional adjacency list achieves an average of 50% speedup over a transactional boosting implementation.