diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md index a339d5058..286855aef 100644 --- a/specs/core/0_beacon-chain.md +++ b/specs/core/0_beacon-chain.md @@ -110,7 +110,7 @@ - [Beacon chain processing](#beacon-chain-processing) - [Beacon chain fork choice rule](#beacon-chain-fork-choice-rule) - [Beacon chain state transition function](#beacon-chain-state-transition-function) - - [State-root caching](#state-root-caching) + - [State caching](#state-caching) - [Per-epoch processing](#per-epoch-processing) - [Helper functions](#helper-functions-1) - [Justification](#justification) @@ -1662,28 +1662,38 @@ def lmd_ghost(store: Store, start_state: BeaconState, start_block: BeaconBlock) We now define the state transition function. At a high level the state transition is made up of four parts: -1. State-root caching, which happens at the start of every slot. +1. State caching, which happens at the start of every slot. 2. The per-epoch transitions, which happens at the start of the first slot of every epoch. 3. The per-slot transitions, which happens at every slot. 4. The per-block transitions, which happens at every block. Transition section notes: -* The state-root caching, caches the state root of the previous slot; -* The per-epoch transitions focus on the [validator](#dfn-validator) registry, including adjusting balances and activating and exiting [validators](#dfn-validator), as well as processing crosslinks and managing block justification/finalization; -* The per-slot transitions focus on the slot counter and block roots records updates; +* The state caching, caches the state root of the previous slot. +* The per-epoch transitions focus on the [validator](#dfn-validator) registry, including adjusting balances and activating and exiting [validators](#dfn-validator), as well as processing crosslinks and managing block justification/finalization. +* The per-slot transitions focus on the slot counter and block roots records updates. * The per-block transitions generally focus on verifying aggregate signatures and saving temporary records relating to the per-block activity in the `BeaconState`. Beacon blocks that trigger unhandled Python exceptions (e.g. out-of-range list accesses) and failed `assert`s during the state transition are considered invalid. -_Note_: If there are skipped slots between a block and its parent block, run the steps in the [state-root](#state-root-caching), [per-epoch](#per-epoch-processing), and [per-slot](#per-slot-processing) sections once for each skipped slot and then once for the slot containing the new block. +_Note_: If there are skipped slots between a block and its parent block, run the steps in the [state-root](#state-caching), [per-epoch](#per-epoch-processing), and [per-slot](#per-slot-processing) sections once for each skipped slot and then once for the slot containing the new block. -### State-root caching +### State caching At every `slot > GENESIS_SLOT` run the following function: ```python -def cache_state_root(state: BeaconState) -> None: - state.latest_state_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = hash_tree_root(state) +def cache_state(state: BeaconState) -> None: + previous_slot_state_root = hash_tree_root(state) + + # store the previous slot's post state transition root + state.latest_state_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = previous_slot_state_root + + # cache state root in stored latest_block_header if empty + if state.latest_block_header.state_root == ZERO_HASH: + state.latest_block_header.state_root = previous_slot_state_root + + # store latest known block for previous slot + state.latest_block_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = hash_tree_root(state.latest_block_header) ``` ### Per-epoch processing @@ -2218,9 +2228,6 @@ At every `slot > GENESIS_SLOT` run the following function: ```python def advance_slot(state: BeaconState) -> None: - if state.latest_block_header.state_root == ZERO_HASH: - state.latest_block_header.state_root = state.latest_block_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] - state.latest_block_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = hash_tree_root(state.latest_block_header) state.slot += 1 ```