The Ethereum Block Selection Puzzle
As anyone familiar with the Ethereum network knows, selecting which transactions to include in the next block is a very important task for miners. This process is known as “block selection,” so understanding the basic mechanics is key to understanding how it works.
A Brief History of Block Selection
In Ethereum 1.x (i.e., until June 2016), miners had to select every transaction that was included in the previous block, regardless of whether it had a chance of being mined or not. This method is often referred to as “all” selection.
However, by July 2017, Ethereum implemented an opt-in model called “selective full” (SFB). Under this new system, miners only have to select transactions that have a certain probability of being included in the next block. In practice, this means that miners can choose which transactions to include in their blocks, taking into account factors such as:
- Block Difficulty: The amount of computing power used by miners and the time it takes to solve the block puzzle.
- Operation Complexity: The amount of data stored or transmitted during each operation.
- Network Congestion
: The level of network activity, including the number of users, fuel prices, and block size.
Algorithm
To choose which transactions to include in their blocks, miners use a specific algorithm that takes these factors into account. Here’s a simplified overview:
- Block Generation: When a new block is mined, it is broadcast to the network.
- Transaction Validation: Nodes confirm the first 3,300 transactions in the block and they are considered “valid” for inclusion in the next block.
- Block Selection Algorithm: Miners use their computing power to analyze each transaction based on factors such as block complexity, transaction complexity, and network congestion. They also consider the hash of each transaction compared to previous transactions in the block.
- Block Creation: The selected transactions are then combined with the remaining unconfirmed transactions from the previous block to form a new block.
How Miners Choose Which Transactions
To choose which transactions to include, miners use a combination of algorithms and heuristics, including:
- Hash Function: Miners use various hash functions, such as SHA-256, to generate a hash of each transaction. They also analyze the distribution of these hashes to gain information about the probability that certain transactions will be included in future blocks.
- Transaction Sorting: Miners sort the selected transactions by hash value and rank them by weight and other factors.
- Heuristic rules: Miners use predefined rules, such as “if operation A is very complex and has low network congestion, include it in the next block” to guide their selection process.
Conclusion
In short, selecting transactions to include in a new Ethereum block is a complex process that involves analyzing various factors such as block complexity, transaction complexity, and network congestion. By understanding these mechanics, miners can optimize their operations and increase their chances of being selected for future blocks.