remove get_epoch_start_slot(...) kludge and update to work exactly as 0.7.1 specifies; remove unused get_attestation_participants_cached(...); update AttestationData to 0.7.1 (being the last data structure, I believe, remaining for such; remove potentially spurious/certainly not-in-spec assertion from compute_committee(...); fix state sim to work with new get_epoch_start_slot/AttestationData/etc setup where it can't stuff all shards' attestations from same slot in the same MIN_ATTESTATION_INCLUSION_DELAY rotating/circular buffer of seq[Attestation]s without more involved shuffling of shard/slot calculation order; fix attestation pool testing to be consistent with get_epoch_start_slot(...) (#302)

beacon_chain/spec/beaconstate.nim

@@ -264,8 +264,6 @@ func get_genesis_beacon_state*(
 
   state
 
-# TODO candidate for spec?
-# https://github.com/ethereum/eth2.0-specs/blob/0.5.1/specs/core/0_beacon-chain.md#on-genesis
 func get_initial_beacon_block*(state: BeaconState): BeaconBlock =
   BeaconBlock(
     slot: GENESIS_SLOT,
@@ -281,9 +279,8 @@ func get_attestation_data_slot*(state: BeaconState,
     offset = (data.crosslink.shard + SHARD_COUNT -
       get_epoch_start_shard(state, data.target_epoch)) mod SHARD_COUNT
 
-  # TODO re-instate once double-check correct conditions in attestation pool
+  get_epoch_start_slot(data.target_epoch) + offset div
-  #get_epoch_start_slot(data.target_epoch) + offset div (committee_count div SLOTS_PER_EPOCH)
+    (committee_count div SLOTS_PER_EPOCH)
-  data.slot
 
 # This is the slower (O(n)), spec-compatible signature.
 func get_attestation_data_slot*(state: BeaconState,
@@ -433,14 +430,6 @@ func get_attesting_indices_seq*(
   toSeq(items(get_attesting_indices(
     state, attestation_data, bitfield, cache)))
 
-# TODO legacy function name; rename, reimplement caching if useful, blob/v0.6.2
-iterator get_attestation_participants_cached*(
-    state: BeaconState, attestation_data: AttestationData, bitfield: BitField,
-    cache: var StateCache): ValidatorIndex =
-  for participant in get_attesting_indices(
-      state, attestation_data, bitfield, cache):
-    yield participant
-
 # https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#convert_to_indexed
 func convert_to_indexed(state: BeaconState, attestation: Attestation,
     stateCache: var StateCache): IndexedAttestation =
@@ -473,8 +462,7 @@ func convert_to_indexed(state: BeaconState, attestation: Attestation,
   ## the conversion here otherwise needs sorting is due to the
   ## usage of HashSet -- order only matters in one place (that
   ## 0.6.3 highlights and explicates) except in that the spec,
-  ## for no obvious reason, verifies it. So, here goes, sort a
+  ## for no obvious reason, verifies it.
-  ## list just so a called function can verify it's sorted.
   IndexedAttestation(
     custody_bit_0_indices: sorted(
       mapIt(custody_bit_0_indices, it.uint64), system.cmp),
@@ -595,7 +583,6 @@ proc makeAttestationData*(
       else: get_block_root_at_slot(state, epoch_start_slot)
 
   AttestationData(
-    slot: state.slot,
     beacon_block_root: beacon_block_root,
     target_root: target_root,
     source_epoch: state.current_justified_epoch,

beacon_chain/spec/datatypes.nim

@@ -117,9 +117,8 @@ type
     signature*: ValidatorSig ##\
     ## BLS aggregate signature
 
-  # https://github.com/ethereum/eth2.0-specs/blob/v0.6.2/specs/core/0_beacon-chain.md#attestationdata
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.7.1/specs/core/0_beacon-chain.md#attestationdata
   AttestationData* = object
-    slot*: Slot # TODO remove this, once figure out attestation pool issues
     # LMD GHOST vote
     beacon_block_root*: Eth2Digest
 

beacon_chain/spec/validator.nim

@@ -118,7 +118,6 @@ func compute_committee(indices: seq[ValidatorIndex], seed: Eth2Digest,
     start = (len(indices).uint64 * index) div count
     endIdx = (len(indices).uint64 * (index + 1)) div count
     key = (indices.len, seed)
-  doAssert endIdx.int - start.int > 0
 
   if key notin stateCache.crosslink_committee_cache:
     stateCache.crosslink_committee_cache[key] =

research/state_sim.nim

@@ -1,7 +1,7 @@
 import
   confutils, stats, times,
   json, strformat,
-  options, sequtils, random,
+  options, sequtils, random, tables,
   ../tests/[testutil],
   ../beacon_chain/spec/[beaconstate, crypto, datatypes, digest, helpers, validator],
   ../beacon_chain/[attestation_pool, extras, ssz, state_transition, fork_choice]
@@ -45,8 +45,8 @@ proc writeJson*(prefix, slot, v: auto) =
   discard open(f, fmt"{prefix:04}-{humaneSlotNum(slot):08}.json", fmWrite)
   write(f, pretty(%*(v)))
 
-cli do(slots = 1945,
+cli do(slots = 448,
-       validators = SLOTS_PER_EPOCH * 8, # One per shard is minimum
+       validators = SLOTS_PER_EPOCH * 9, # One per shard is minimum
        json_interval = SLOTS_PER_EPOCH,
        prefix = 0,
        attesterRatio {.desc: "ratio of validators that attest in each round"} = 0.9,
@@ -58,7 +58,7 @@ cli do(slots = 1945,
     genesisBlock = get_initial_beacon_block(genesisState)
 
   var
-    attestations: array[MIN_ATTESTATION_INCLUSION_DELAY, seq[Attestation]]
+    attestations = initTable[Slot, seq[Attestation]]()
     state = genesisState
     latest_block_root = signing_root(genesisBlock)
     timers: array[Timers, RunningStat]
@@ -78,10 +78,13 @@ cli do(slots = 1945,
     maybeWrite()
 
     let
-      attestations_idx = state.slot mod MIN_ATTESTATION_INCLUSION_DELAY
+      attestations_idx = state.slot
-      body = BeaconBlockBody(attestations: attestations[attestations_idx])
+      body = BeaconBlockBody(
+        attestations: attestations.getOrDefault(attestations_idx))
 
-    attestations[attestations_idx] = @[]
+    attestations.del attestations_idx
+    doAssert len(attestations) <=
+      (SLOTS_PER_EPOCH.int + MIN_ATTESTATION_INCLUSION_DELAY.int)
 
     let t =
       if (state.slot > GENESIS_SLOT and
@@ -127,9 +130,19 @@ cli do(slots = 1945,
           # add the attestation if any of the validators attested, as given
           # by the randomness. We have to delay when the attestation is
           # actually added to the block per the attestation delay rule!
-          attestations[
+          let target_slot =
-            (state.slot + MIN_ATTESTATION_INCLUSION_DELAY - 1) mod
+            get_attestation_data_slot(state, attestation.data) +
-              MIN_ATTESTATION_INCLUSION_DELAY].add attestation
+            MIN_ATTESTATION_INCLUSION_DELAY - 1
+
+          ## In principle, should enumerate possible shard/slot combinations by
+          ## inverting get_attestation_data_slot(...), but this works. Could be
+          ## filtering earlier if we know that this attestation's being created
+          ## too late to be useful, as well.
+          if target_slot > attestations_idx:
+            var target_slot_attestations =
+              getOrDefault(attestations, target_slot)
+            target_slot_attestations.add attestation
+            attestations[target_slot] = target_slot_attestations
 
     flushFile(stdout)
 

tests/test_attestation_pool.nim

@@ -40,7 +40,7 @@ suite "Attestation pool processing" & preset():
       let
         # Create an attestation for slot 1!
         crosslink_committee = get_crosslink_committee(state.data.data,
-          slot_to_epoch(state.data.data.slot), 0, cache)
+          slot_to_epoch(state.data.data.slot), 1, cache)
         attestation = makeAttestation(
           state.data.data, state.blck.root, crosslink_committee[0])
 
@@ -61,7 +61,7 @@ suite "Attestation pool processing" & preset():
       let
         # Create an attestation for slot 1!
         cc0 = get_crosslink_committee(state.data.data,
-          slot_to_epoch(state.data.data.slot), 0, cache)
+          slot_to_epoch(state.data.data.slot), 1, cache)
         attestation0 = makeAttestation(
           state.data.data, state.blck.root, cc0[0])
 
@@ -69,7 +69,7 @@ suite "Attestation pool processing" & preset():
 
       let
         cc1 = get_crosslink_committee(state.data.data,
-          slot_to_epoch(state.data.data.slot), 0, cache)
+          slot_to_epoch(state.data.data.slot), 2, cache)
         attestation1 = makeAttestation(
           state.data.data, state.blck.root, cc1[0])
 
@@ -77,7 +77,8 @@ suite "Attestation pool processing" & preset():
       pool.add(state.data.data, attestation1)
       pool.add(state.data.data, attestation0)
 
-      for i in 0..<MIN_ATTESTATION_INCLUSION_DELAY.int - 1: advanceState(state.data)
+      for i in 0..<MIN_ATTESTATION_INCLUSION_DELAY.int - 1:
+        advanceState(state.data)
 
       let attestations = pool.getAttestationsForBlock(
         state.data.data, state.data.data.slot + 1)
@@ -91,7 +92,7 @@ suite "Attestation pool processing" & preset():
       let
         # Create an attestation for slot 1!
         cc0 = get_crosslink_committee(state.data.data,
-          slot_to_epoch(state.data.data.slot), 0, cache)
+          slot_to_epoch(state.data.data.slot), 1, cache)
         attestation0 = makeAttestation(
           state.data.data, state.blck.root, cc0[0])
         attestation1 = makeAttestation(
@@ -115,7 +116,7 @@ suite "Attestation pool processing" & preset():
       var
         # Create an attestation for slot 1!
         cc0 = get_crosslink_committee(state.data.data,
-          slot_to_epoch(state.data.data.slot), 0, cache)
+          slot_to_epoch(state.data.data.slot), 1, cache)
         attestation0 = makeAttestation(
           state.data.data, state.blck.root, cc0[0])
         attestation1 = makeAttestation(
@@ -140,7 +141,7 @@ suite "Attestation pool processing" & preset():
       var
         # Create an attestation for slot 1!
         cc0 = get_crosslink_committee(state.data.data,
-          slot_to_epoch(state.data.data.slot), 0, cache)
+          slot_to_epoch(state.data.data.slot), 1, cache)
         attestation0 = makeAttestation(
           state.data.data, state.blck.root, cc0[0])
         attestation1 = makeAttestation(