From 4286f85a68a7b2abdca249cd02482616840e5f86 Mon Sep 17 00:00:00 2001 From: Alex Stokes Date: Wed, 12 May 2021 11:05:41 -0700 Subject: [PATCH] Update validator guide with restricted sync committee computation --- specs/altair/validator.md | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/specs/altair/validator.md b/specs/altair/validator.md index 67e5914d1..4aee98ad4 100644 --- a/specs/altair/validator.md +++ b/specs/altair/validator.md @@ -177,7 +177,6 @@ At any given `epoch`, the `BeaconState` contains the current `SyncCommittee` and Once every `EPOCHS_PER_SYNC_COMMITTEE_PERIOD` epochs, the next `SyncCommittee` becomes the current `SyncCommittee` and the next committee is computed and stored. *Note*: The data required to compute a given committee is not cached in the `BeaconState` after committees are calculated at the period boundaries. -This means that calling `get_sync_commitee()` in a given `epoch` can return a different result than what was computed during the relevant epoch transition. For this reason, *always* get committee assignments via the fields of the `BeaconState` (`current_sync_committee` and `next_sync_committee`) or use the above reference code. A validator should plan for future sync committee assignments by noting which sync committee periods they are selected for participation. @@ -229,12 +228,12 @@ def process_sync_committee_contributions(block: BeaconBlock, contributions: Set[SyncCommitteeContribution]) -> None: sync_aggregate = SyncAggregate() signatures = [] + sync_subcommittee_size = SYNC_COMMITTEE_SIZE // SYNC_COMMITTEE_SUBNET_COUNT for contribution in contributions: subcommittee_index = contribution.subcommittee_index for index, participated in enumerate(contribution.aggregation_bits): if participated: - sync_subcommittee_size = SYNC_COMMITTEE_SIZE // SYNC_COMMITTEE_SUBNET_COUNT participant_index = sync_subcommittee_size * subcommittee_index + index sync_aggregate.sync_committee_bits[participant_index] = True signatures.append(contribution.signature) @@ -367,7 +366,7 @@ Set `contribution.subcommittee_index` to the index for the subcommittee index co ###### Aggregation bits Let `contribution.aggregation_bits` be a `Bitvector[SYNC_COMMITTEE_SIZE // SYNC_COMMITTEE_SUBNET_COUNT]`, where the `index`th bit is set in the `Bitvector` for each corresponding validator included in this aggregate from the corresponding subcommittee. -An aggregator finds the index in the sync committee (as returned by `get_sync_committee_indices()`) for a given validator referenced by `sync_committee_signature.validator_index` and maps the sync committee index to an index in the subcommittee (along with the prior `subcommittee_index`). This index within the subcommittee is set in `contribution.aggegration_bits`. +An aggregator finds the index in the sync committee (as determined by a reverse pubkey lookup on `state.current_sync_committee.pubkeys`) for a given validator referenced by `sync_committee_signature.validator_index` and maps the sync committee index to an index in the subcommittee (along with the prior `subcommittee_index`). This index within the subcommittee is set in `contribution.aggegration_bits`. For example, if a validator with index `2044` is pseudo-randomly sampled to sync committee index `135`. This sync committee index maps to `subcommittee_index` `1` with position `7` in the `Bitvector` for the contribution.