## Proposed Changes
This PR has two aims: to speed up attestation packing in the op pool, and to fix bugs in the verification of attester slashings, proposer slashings and voluntary exits. The changes are bundled into a single database schema upgrade (v12).
Attestation packing is sped up by removing several inefficiencies:
- No more recalculation of `attesting_indices` during packing.
- No (unnecessary) examination of the `ParticipationFlags`: a bitfield suffices. See `RewardCache`.
- No re-checking of attestation validity during packing: the `AttestationMap` provides attestations which are "correct by construction" (I have checked this using Hydra).
- No SSZ re-serialization for the clunky `AttestationId` type (it can be removed in a future release).
So far the speed-up seems to be roughly 2-10x, from 500ms down to 50-100ms.
Verification of attester slashings, proposer slashings and voluntary exits is fixed by:
- Tracking the `ForkVersion`s that were used to verify each message inside the `SigVerifiedOp`. This allows us to quickly re-verify that they match the head state's opinion of what the `ForkVersion` should be at the epoch(s) relevant to the message.
- Storing the `SigVerifiedOp` on disk rather than the raw operation. This allows us to continue track the fork versions after a reboot.
This is mostly contained in this commit 52bb1840ae.
## Additional Info
The schema upgrade uses the justified state to re-verify attestations and compute `attesting_indices` for them. It will drop any attestations that fail to verify, by the logic that attestations are most valuable in the few slots after they're observed, and are probably stale and useless by the time a node restarts. Exits and proposer slashings and similarly re-verified to obtain `SigVerifiedOp`s.
This PR contains a runtime killswitch `--paranoid-block-proposal` which opts out of all the optimisations in favour of closely verifying every included message. Although I'm quite sure that the optimisations are correct this flag could be useful in the event of an unforeseen emergency.
Finally, you might notice that the `RewardCache` appears quite useless in its current form because it is only updated on the hot-path immediately before proposal. My hope is that in future we can shift calls to `RewardCache::update` into the background, e.g. while performing the state advance. It is also forward-looking to `tree-states` compatibility, where iterating and indexing `state.{previous,current}_epoch_participation` is expensive and needs to be minimised.
## Issue Addressed
NA
## Proposed Changes
- Uses a `Vec` in `SingleEpochParticipationCache` rather than `HashMap` to speed up processing times at the cost of memory usage.
- Cache the result of `integer_sqrt` rather than recomputing for each validator.
- Cache `state.previous_epoch` rather than recomputing it for each validator.
### Benchmarks
Benchmarks on a recent mainnet state using #3252 to get timing.
#### Without this PR
```
lcli skip-slots --state-path /tmp/state-0x3cdc.ssz --partial-state-advance --slots 32 --state-root 0x3cdc33cd02713d8d6cc33a6dbe2d3a5bf9af1d357de0d175a403496486ff845e --runs 10
[2022-06-09T08:21:02Z INFO lcli::skip_slots] Using mainnet spec
[2022-06-09T08:21:02Z INFO lcli::skip_slots] Advancing 32 slots
[2022-06-09T08:21:02Z INFO lcli::skip_slots] Doing 10 runs
[2022-06-09T08:21:02Z INFO lcli::skip_slots] State path: "/tmp/state-0x3cdc.ssz"
SSZ decoding /tmp/state-0x3cdc.ssz: 43ms
[2022-06-09T08:21:03Z INFO lcli::skip_slots] Run 0: 245.718794ms
[2022-06-09T08:21:03Z INFO lcli::skip_slots] Run 1: 245.364782ms
[2022-06-09T08:21:03Z INFO lcli::skip_slots] Run 2: 255.866179ms
[2022-06-09T08:21:04Z INFO lcli::skip_slots] Run 3: 243.838909ms
[2022-06-09T08:21:04Z INFO lcli::skip_slots] Run 4: 250.431425ms
[2022-06-09T08:21:04Z INFO lcli::skip_slots] Run 5: 248.68765ms
[2022-06-09T08:21:04Z INFO lcli::skip_slots] Run 6: 262.051113ms
[2022-06-09T08:21:05Z INFO lcli::skip_slots] Run 7: 264.293967ms
[2022-06-09T08:21:05Z INFO lcli::skip_slots] Run 8: 293.202007ms
[2022-06-09T08:21:05Z INFO lcli::skip_slots] Run 9: 264.552017ms
```
#### With this PR:
```
lcli skip-slots --state-path /tmp/state-0x3cdc.ssz --partial-state-advance --slots 32 --state-root 0x3cdc33cd02713d8d6cc33a6dbe2d3a5bf9af1d357de0d175a403496486ff845e --runs 10
[2022-06-09T08:57:59Z INFO lcli::skip_slots] Run 0: 73.898678ms
[2022-06-09T08:57:59Z INFO lcli::skip_slots] Run 1: 75.536978ms
[2022-06-09T08:57:59Z INFO lcli::skip_slots] Run 2: 75.176104ms
[2022-06-09T08:57:59Z INFO lcli::skip_slots] Run 3: 76.460828ms
[2022-06-09T08:57:59Z INFO lcli::skip_slots] Run 4: 75.904195ms
[2022-06-09T08:58:00Z INFO lcli::skip_slots] Run 5: 75.53077ms
[2022-06-09T08:58:00Z INFO lcli::skip_slots] Run 6: 74.745572ms
[2022-06-09T08:58:00Z INFO lcli::skip_slots] Run 7: 75.823489ms
[2022-06-09T08:58:00Z INFO lcli::skip_slots] Run 8: 74.892055ms
[2022-06-09T08:58:00Z INFO lcli::skip_slots] Run 9: 76.333569ms
```
## Additional Info
NA
## Issue Addressed
NA
## Proposed Changes
Adds some more testing for Altair to the op pool. Credits to @michaelsproul for some appropriated efforts here.
## Additional Info
NA
Co-authored-by: Michael Sproul <michael@sigmaprime.io>
## Proposed Changes
Implement the consensus changes necessary for the upcoming Altair hard fork.
## Additional Info
This is quite a heavy refactor, with pivotal types like the `BeaconState` and `BeaconBlock` changing from structs to enums. This ripples through the whole codebase with field accesses changing to methods, e.g. `state.slot` => `state.slot()`.
Co-authored-by: realbigsean <seananderson33@gmail.com>
## Proposed Changes
Use two instances of max cover when packing attestations into blocks: one for the previous epoch, and one for the current epoch. This reduces the amount of computation done by roughly half due to the `O(n^2)` running time of max cover (`2 * (n/2)^2 = n^2/2`). This should help alleviate some load on block proposal, particularly on Prater.
