eth2.0-specs/specs/_features/whisk/fork.md

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# Whisk -- Fork Logic
**Notice**: This document is a work-in-progress for researchers and implementers.
## Table of contents
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- [Introduction](#introduction)
- [Configuration](#configuration)
- [Fork to Whisk](#fork-to-whisk)
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## Introduction
This document describes the process of Whisk upgrade.
```
"""
WHISK_FORK_EPOCH
| cooldown
| | ||
v vsvv
--+~~~~~~~~~~~~~~~~~~~~~----+-
shuffling ^
|
|
proposer selection
candidate selection
"""
```
## Configuration
Warning: this configuration is not definitive.
| Name | Value |
| -------------------- | ----------------------- |
| `WHISK_FORK_VERSION` | `Version('0x08000000')` |
| `WHISK_FORK_EPOCH` | `Epoch(18446744073709551615)` **TBD** |
## Fork to Whisk
If `state.slot % SLOTS_PER_EPOCH == 0` and `compute_epoch_at_slot(state.slot) == WHISK_FORK_EPOCH`, an irregular state change is made to upgrade to Whisk. `WHISK_FORK_EPOCH` must be a multiple of `WHISK_RUN_DURATION_IN_EPOCHS`.
The upgrade occurs after the completion of the inner loop of `process_slots` that sets `state.slot` equal to `WHISK_FORK_EPOCH * SLOTS_PER_EPOCH`.
This ensures that we drop right into the beginning of the shuffling phase but without `process_whisk_epoch()` triggering for this Whisk run. Hence we handle all the setup ourselves in `upgrade_to_whisk()` below.
```python
def upgrade_to_whisk(pre: capella.BeaconState) -> BeaconState:
# Compute initial unsafe trackers for all validators
ks = [get_initial_whisk_k(ValidatorIndex(validator_index), 0) for validator_index in range(len(pre.validators))]
whisk_k_commitments = [get_k_commitment(k) for k in ks]
whisk_trackers = [get_initial_tracker(k) for k in ks]
epoch = get_current_epoch(pre)
post = BeaconState(
# Versioning
genesis_time=pre.genesis_time,
genesis_validators_root=pre.genesis_validators_root,
slot=pre.slot,
fork=Fork(
previous_version=pre.fork.current_version,
current_version=WHISK_FORK_VERSION,
epoch=epoch,
),
# History
latest_block_header=pre.latest_block_header,
block_roots=pre.block_roots,
state_roots=pre.state_roots,
historical_roots=pre.historical_roots,
# Eth1
eth1_data=pre.eth1_data,
eth1_data_votes=pre.eth1_data_votes,
eth1_deposit_index=pre.eth1_deposit_index,
# Registry
validators=[],
balances=pre.balances,
# Randomness
randao_mixes=pre.randao_mixes,
# Slashings
slashings=pre.slashings,
# Participation
previous_epoch_participation=pre.previous_epoch_participation,
current_epoch_participation=pre.current_epoch_participation,
# Finality
justification_bits=pre.justification_bits,
previous_justified_checkpoint=pre.previous_justified_checkpoint,
current_justified_checkpoint=pre.current_justified_checkpoint,
finalized_checkpoint=pre.finalized_checkpoint,
# Inactivity
inactivity_scores=pre.inactivity_scores,
# Sync
current_sync_committee=pre.current_sync_committee,
next_sync_committee=pre.next_sync_committee,
# Execution-layer
latest_execution_payload_header=pre.latest_execution_payload_header,
# Withdrawals
next_withdrawal_index=pre.next_withdrawal_index,
next_withdrawal_validator_index=pre.next_withdrawal_validator_index,
# Deep history valid from Capella onwards
historical_summaries=pre.historical_summaries,
# Whisk
whisk_proposer_trackers=[WhiskTracker() for _ in range(WHISK_PROPOSER_TRACKERS_COUNT)], # [New in Whisk]
whisk_candidate_trackers=[WhiskTracker() for _ in range(WHISK_CANDIDATE_TRACKERS_COUNT)], # [New in Whisk]
whisk_trackers=whisk_trackers, # [New in Whisk]
whisk_k_commitments=whisk_k_commitments, # [New in Whisk]
)
# Do a candidate selection followed by a proposer selection so that we have proposers for the upcoming day
# Use an old epoch when selecting candidates so that we don't get the same seed as in the next candidate selection
select_whisk_candidate_trackers(post, Epoch(saturating_sub(epoch, WHISK_PROPOSER_SELECTION_GAP + 1)))
select_whisk_proposer_trackers(post, epoch)
# Do a final round of candidate selection.
# We need it so that we have something to shuffle over the upcoming shuffling phase.
select_whisk_candidate_trackers(post, epoch)
return post
```