Merge pull request #662 from ethereum/vbuterin-patch-5

Rename shard_block_root -> crosslink_data_root
ethereum · Feb 22, 2019 · 06e6496 · 06e6496
2 parents a683416 + b89cd23
commit 06e6496
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diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
@@ -356,8 +356,8 @@ The following data structures are defined as [SimpleSerialize (SSZ)](https://git
     'beacon_block_root': 'bytes32',
     # Root of the ancestor at the epoch boundary
     'epoch_boundary_root': 'bytes32',
-    # Shard block's hash of root
-    'shard_block_root': 'bytes32',
+    # Data from the shard since the last attestation
+    'crosslink_data_root': 'bytes32',
     # Last crosslink
     'latest_crosslink': Crosslink,
     # Last justified epoch in the beacon state
@@ -578,8 +578,8 @@ The following data structures are defined as [SimpleSerialize (SSZ)](https://git
 {
     # Epoch number
     'epoch': 'uint64',
-    # Shard block root
-    'shard_block_root': 'bytes32',
+    # Shard data since the previous crosslink
+    'crosslink_data_root': 'bytes32',
 }
 ```
 
@@ -1461,7 +1461,7 @@ def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
         finalized_epoch=GENESIS_EPOCH,
 
         # Recent state
-        latest_crosslinks=[Crosslink(epoch=GENESIS_EPOCH, shard_block_root=ZERO_HASH) for _ in range(SHARD_COUNT)],
+        latest_crosslinks=[Crosslink(epoch=GENESIS_EPOCH, crosslink_data_root=ZERO_HASH) for _ in range(SHARD_COUNT)],
         latest_block_roots=[ZERO_HASH for _ in range(LATEST_BLOCK_ROOTS_LENGTH)],
         latest_active_index_roots=[ZERO_HASH for _ in range(LATEST_ACTIVE_INDEX_ROOTS_LENGTH)],
         latest_slashed_balances=[0 for _ in range(LATEST_SLASHED_EXIT_LENGTH)],
@@ -1661,7 +1661,7 @@ For each `attestation` in `block.body.attestations`:
 * Verify that `state.slot < attestation.data.slot + SLOTS_PER_EPOCH.
 * Verify that `attestation.data.justified_epoch` is equal to `state.justified_epoch if slot_to_epoch(attestation.data.slot + 1) >= get_current_epoch(state) else state.previous_justified_epoch`.
 * Verify that `attestation.data.justified_block_root` is equal to `get_block_root(state, get_epoch_start_slot(attestation.data.justified_epoch))`.
-* Verify that either (i) `state.latest_crosslinks[attestation.data.shard] == attestation.data.latest_crosslink` or (ii) `state.latest_crosslinks[attestation.data.shard] == Crosslink(shard_block_root=attestation.data.shard_block_root, epoch=slot_to_epoch(attestation.data.slot))`.
+* Verify that either (i) `state.latest_crosslinks[attestation.data.shard] == attestation.data.latest_crosslink` or (ii) `state.latest_crosslinks[attestation.data.shard] == Crosslink(crosslink_data_root=attestation.data.crosslink_data_root, epoch=slot_to_epoch(attestation.data.slot))`.
 * Verify bitfields and aggregate signature:
 
 ```python
@@ -1694,7 +1694,7 @@ For each `attestation` in `block.body.attestations`:
     )
 ```
 
-* [TO BE REMOVED IN PHASE 1] Verify that `attestation.data.shard_block_root == ZERO_HASH`.
+* [TO BE REMOVED IN PHASE 1] Verify that `attestation.data.crosslink_data_root == ZERO_HASH`.
 * Append `PendingAttestation(data=attestation.data, aggregation_bitfield=attestation.aggregation_bitfield, custody_bitfield=attestation.custody_bitfield, inclusion_slot=state.slot)` to `state.latest_attestations`.
 
 ##### Deposits
@@ -1802,9 +1802,9 @@ The steps below happen when `(state.slot + 1) % SLOTS_PER_EPOCH == 0`.
 
 For every `slot in range(get_epoch_start_slot(previous_epoch), get_epoch_start_slot(next_epoch))`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
 
-* Let `shard_block_root` be `state.latest_crosslinks[shard].shard_block_root`
-* Let `attesting_validator_indices(crosslink_committee, shard_block_root)` be the union of the [validator](#dfn-validator) index sets given by `[get_attestation_participants(state, a.data, a.aggregation_bitfield) for a in current_epoch_attestations + previous_epoch_attestations if a.data.shard == shard and a.data.shard_block_root == shard_block_root]`.
-* Let `winning_root(crosslink_committee)` be equal to the value of `shard_block_root` such that `get_total_balance(state, attesting_validator_indices(crosslink_committee, shard_block_root))` is maximized (ties broken by favoring lower `shard_block_root` values).
+* Let `crosslink_data_root` be `state.latest_crosslinks[shard].crosslink_data_root`
+* Let `attesting_validator_indices(crosslink_committee, crosslink_data_root)` be the union of the [validator](#dfn-validator) index sets given by `[get_attestation_participants(state, a.data, a.aggregation_bitfield) for a in current_epoch_attestations + previous_epoch_attestations if a.data.shard == shard and a.data.crosslink_data_root == crosslink_data_root]`.
+* Let `winning_root(crosslink_committee)` be equal to the value of `crosslink_data_root` such that `get_total_balance(state, attesting_validator_indices(crosslink_committee, crosslink_data_root))` is maximized (ties broken by favoring lower `crosslink_data_root` values).
 * Let `attesting_validators(crosslink_committee)` be equal to `attesting_validator_indices(crosslink_committee, winning_root(crosslink_committee))` for convenience.
 * Let `total_attesting_balance(crosslink_committee) = get_total_balance(state, attesting_validators(crosslink_committee))`.
 
@@ -1845,7 +1845,7 @@ Finally, update the following:
 
 For every `slot in range(get_epoch_start_slot(previous_epoch), get_epoch_start_slot(next_epoch))`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
 
-* Set `state.latest_crosslinks[shard] = Crosslink(epoch=slot_to_epoch(slot), shard_block_root=winning_root(crosslink_committee))` if `3 * total_attesting_balance(crosslink_committee) >= 2 * get_total_balance(crosslink_committee)`.
+* Set `state.latest_crosslinks[shard] = Crosslink(epoch=slot_to_epoch(slot), crosslink_data_root=winning_root(crosslink_committee))` if `3 * total_attesting_balance(crosslink_committee) >= 2 * get_total_balance(crosslink_committee)`.
 
 #### Rewards and penalties
 

diff --git a/specs/core/1_shard-data-chains.md b/specs/core/1_shard-data-chains.md
@@ -16,10 +16,10 @@
             - [Max operations per block](#max-operations-per-block)
             - [Signature domains](#signature-domains)
     - [Helper functions](#helper-functions)
-            - [get_split_offset](#get_split_offset)
-            - [get_shuffled_committee](#get_shuffled_committee)
-            - [get_persistent_committee](#get_persistent_committee)
-            - [get_shard_proposer_index](#get_shard_proposer_index)
+            - [`get_split_offset`](#get_split_offset)
+            - [`get_shuffled_committee`](#get_shuffled_committee)
+            - [`get_persistent_committee`](#get_persistent_committee)
+            - [`get_shard_proposer_index`](#get_shard_proposer_index)
     - [Data Structures](#data-structures)
         - [Shard chain blocks](#shard-chain-blocks)
     - [Shard block processing](#shard-block-processing)
@@ -100,7 +100,7 @@ Phase 1 depends upon all of the constants defined in [Phase 0](0_beacon-chain.md
 
 ## Helper functions
 
-#### get_split_offset
+#### `get_split_offset`
 
 ````python
 def get_split_offset(list_size: int, chunks: int, index: int) -> int:
@@ -111,7 +111,7 @@ def get_split_offset(list_size: int, chunks: int, index: int) -> int:
   return (len(list_size) * index) // chunks
 ````
 
-#### get_shuffled_committee
+#### `get_shuffled_committee`
 
 ```python
 def get_shuffled_committee(state: BeaconState,
@@ -130,7 +130,7 @@ def get_shuffled_committee(state: BeaconState,
     ]
 ```
 
-#### get_persistent_committee
+#### `get_persistent_committee`
 
 ```python
 def get_persistent_committee(state: BeaconState,
@@ -158,7 +158,8 @@ def get_persistent_committee(state: BeaconState,
         [i for i in later_committee if epoch % PERSISTENT_COMMITTEE_PERIOD >= get_switchover_epoch(i)]
     )))
 ```
-#### get_shard_proposer_index
+
+#### `get_shard_proposer_index`
 
 ```python
 def get_shard_proposer_index(state: BeaconState,
@@ -289,7 +290,7 @@ The `shard_chain_commitment` is only valid if it equals `compute_commitment(head
 
 ### Shard block fork choice rule
 
-The fork choice rule for any shard is LMD GHOST using the shard chain attestations of the persistent committee and the beacon chain attestations of the crosslink committee currently assigned to that shard, but instead of being rooted in the genesis it is rooted in the block referenced in the most recent accepted crosslink (ie. `state.crosslinks[shard].shard_block_root`). Only blocks whose `beacon_chain_ref` is the block in the main beacon chain at the specified `slot` should be considered (if the beacon chain skips a slot, then the block at that slot is considered to be the block in the beacon chain at the highest slot lower than a slot).
+The fork choice rule for any shard is LMD GHOST using the shard chain attestations of the persistent committee and the beacon chain attestations of the crosslink committee currently assigned to that shard, but instead of being rooted in the genesis it is rooted in the latest block referenced in the most recent accepted crosslink (ie. `state.crosslinks[shard].crosslink_data_root`). Only blocks whose `beacon_chain_ref` is the block in the main beacon chain at the specified `slot` should be considered (if the beacon chain skips a slot, then the block at that slot is considered to be the block in the beacon chain at the highest slot lower than a slot).
 
 # Updates to the beacon chain
 

diff --git a/specs/validator/0_beacon-chain-validator.md b/specs/validator/0_beacon-chain-validator.md
@@ -41,7 +41,7 @@ __NOTICE__: This document is a work-in-progress for researchers and implementers
                 - [Shard](#shard)
                 - [Beacon block root](#beacon-block-root)
                 - [Epoch boundary root](#epoch-boundary-root)
-                - [Shard block root](#shard-block-root)
+                - [Crosslink data root](#crosslink-data-root)
                 - [Latest crosslink](#latest-crosslink)
                 - [Justified epoch](#justified-epoch)
                 - [Justified block root](#justified-block-root)
@@ -266,9 +266,9 @@ _Note:_ This can be looked up in the state using:
 * Let `epoch_start_slot = get_epoch_start_slot(slot_to_epoch(head.slot))`.
 * Set `epoch_boundary_root = hash_tree_root(head) if epoch_start_slot == head.slot else get_block_root(state, epoch_start_slot)`.
 
-##### Shard block root
+##### Crosslink data root
 
-Set `attestation_data.shard_block_root = ZERO_HASH`.
+Set `attestation_data.crosslink_data_root = ZERO_HASH`.
 
 _Note:_ This is a stub for phase 0.