Why is read_origins `Vec` in `ReadSet`?

[jackwener]

I think MemoryLocation just can be read once in a Tx.

So

ReadSet = HashMap<MemoryLocationHash, ReadOrigin, BuildIdentityHasher>;

is enough.

I also run test mainnet, read_origins len always is 1.

Is there something I didn't consider? @hai-rise

[hai-rise]

It used to be a single ReadOrigin until we added lazy updates, which would store a chain of transactions that lazy updated the memory location until we hit a "strict"/"absolute" origin. This should happen for blocks with an explicit read on the beneficiary balance (like the validator spends ETH in their block), or blocks with many raw ETH transfers that we lazy update the senders and recipients.

I had a talk about pevm recently at Paradigm Frontiers with intuitive examples: https://www.youtube.com/live/1xQTHCjcWVk?si=YNGOc9zvqjMR5hCP&t=11794

Will write detailed doc on lazy updates and all our changes to the original Block-STM designs soon 🙏.

[jackwener]

Thank you! I get it.