Struct QueuedSolution

pub struct QueuedSolution<T: Config>(/* private fields */);

A wrapper interface for the storage items related to the queued solution.

It wraps the following:

• QueuedSolutionX
• QueuedSolutionY
• QueuedValidVariant
• QueuedSolutionScore
• QueuedSolutionBackings

As the name suggests, QueuedValidVariant points to the correct variant between QueuedSolutionX and QueuedSolutionY. In the context of this pallet, by VALID and INVALID variant we mean either of these two storage items, based on the value of QueuedValidVariant.

Round Index

Much like Snapshot in the parent crate, these storage items are mapping whereby their first key is the round index. None of the APIs in QueuedSolution expose this, as on-chain, we should ONLY ever be reading the current round’s associated data.

Having this extra key paves the way for lazy deletion in the future.

Invariants

The following conditions must be met at all times for this group of storage items to be sane.

• QueuedSolutionScore must always be correct. In other words, it should correctly be the score of QueuedValidVariant.
• QueuedSolutionScore must always be Config::SolutionImprovementThreshold better than MinimumScore.
• The number of existing keys in QueuedSolutionBackings must always match that of the INVALID variant.

Moreover, the following conditions must be met when this pallet is in Status::Nothing, meaning that no ongoing asynchronous verification is ongoing.

• No keys should exist in the INVALID variant.
  • This implies that no data should exist in QueuedSolutionBackings.

Note that some keys might exist in the queued variant, but since partial solutions (having less than T::Pages pages) are in principle correct, we cannot assert anything on the number of keys in the VALID variant. In fact, an empty solution with score of [0, 0, 0] can also be correct.

No additional conditions must be met when the pallet is in Status::Ongoing. The number of pages in