# An Empirical Study of Speculative Concurrency in Ethereum Smart Contracts

## TL;DR

This study evaluates speculative concurrency techniques for Ethereum smart contracts, showing significant speed-ups in execution that decrease over time, and identifying key contracts responsible for data conflicts.

## Contribution

It provides an empirical analysis of speculative execution in Ethereum, demonstrating potential speed-ups and identifying conflict-prone contracts.

## Key findings

- Estimated speed-ups of 8x in 2016, declining to 2x in 2017
- A small set of contracts cause most data conflicts
- Speed-up measured via gas costs and instruction counts

## Abstract

We use historical data to estimate the potential benefit of speculative techniques for executing Ethereum smart contracts in parallel. We replay transaction traces of sampled blocks from the Ethereum blockchain over time, using a simple speculative execution engine. In this engine, miners attempt to execute all transactions in a block in parallel, rolling back those that cause data conflicts. Aborted transactions are then executed sequentially. Validators execute the same schedule as miners. We find that our speculative technique yields estimated speed-ups starting at about 8-fold in 2016, declining to about 2-fold at the end of 2017, where speed-up is measured using either gas costs or instruction counts. We also observe that a small set of contracts are responsible for many data conflicts resulting from speculative concurrent execution.