get crosslink committees by slot

configs/minimal.yaml

@@ -5,7 +5,7 @@
 # ---------------------------------------------------------------
 
 # [customized] Just 2 committees for slot for testing purposes
-MAX_COMMITTEES_PER_SLOT: 2
+MAX_COMMITTEES_PER_SLOT: 4
 # [customized] unsecure, but fast
 TARGET_COMMITTEE_SIZE: 4
 # 2**12 (= 4,096)

specs/core/0_beacon-chain.md

@@ -858,19 +858,18 @@ def get_seed(state: BeaconState, epoch: Epoch, domain_type: DomainType) -> Hash:
     return hash(domain_type + int_to_bytes(epoch, length=8) + mix)
 ```
 
-
+#### `get_committees_per_slot`
-#### `get_committee_count`
 
 ```python
-def get_committee_count(state: BeaconState, epoch: Epoch) -> uint64:
+def get_committees_per_slot(state: BeaconState, slot: Slot) -> uint64:
     """
-    Return the number of committees at ``epoch``.
+    Return the number of committees at ``slot``.
     """
-    committees_per_slot = max(1, min(
+    epoch = compute_epoch_of_slot(slot)
+    return max(1, min(
         MAX_COMMITTEES_PER_SLOT,
         len(get_active_validator_indices(state, epoch)) // SLOTS_PER_EPOCH // TARGET_COMMITTEE_SIZE,
     ))
-    return committees_per_slot * SLOTS_PER_EPOCH
 ```
 
 #### `get_crosslink_committee`
@@ -878,20 +877,19 @@ def get_committee_count(state: BeaconState, epoch: Epoch) -> uint64:
 ```python
 def get_crosslink_committee(state: BeaconState, slot: Slot, index: uint64) -> Sequence[ValidatorIndex]:
     """
-    Return the crosslink committee at ``epoch`` for ``index``.
+    Return the crosslink committee at ``slot`` for ``index``.
     """
     epoch = compute_epoch_of_slot(slot)
-    committees_per_slot = get_committee_count(state, epoch) // SLOTS_PER_EPOCH
+    committees_per_slot = get_committees_per_slot(state, slot)
     slot_start_index = get_slot_start_index(state, slot)
     slot_offset = (index + MAX_COMMITTEES_PER_SLOT - slot_start_index) % MAX_COMMITTEES_PER_SLOT
     epoch_offset = slot_offset + (slot % SLOTS_PER_EPOCH) * committees_per_slot
-    print(epoch_offset)
 
     return compute_committee(
         indices=get_active_validator_indices(state, epoch),
         seed=get_seed(state, epoch, DOMAIN_BEACON_ATTESTER),
         index=epoch_offset,
-        count=get_committee_count(state, epoch),
+        count=committees_per_slot * SLOTS_PER_EPOCH,
     )
 ```
 
@@ -903,8 +901,9 @@ def get_slot_start_index(state: BeaconState, slot: Slot) -> uint64:
     Return the start index of the 0th committee at ``slot``.
     """
     epoch = compute_epoch_of_slot(slot)
-    committees_per_slot = get_committee_count(state, epoch) // SLOTS_PER_EPOCH
+    committees_per_slot = get_committees_per_slot(state, slot)
-    slot_start_index = ((slot % SLOTS_PER_EPOCH) * committees_per_slot + get_start_index(state, epoch)) % MAX_COMMITTEES_PER_SLOT
+    start_index = get_start_index(state, epoch)
+    slot_start_index = ((slot % SLOTS_PER_EPOCH) * committees_per_slot + start_index) % MAX_COMMITTEES_PER_SLOT
     return slot_start_index
 ```
 
@@ -932,7 +931,7 @@ def get_index_delta(state: BeaconState, epoch: Epoch) -> uint64:
     """
     Return the amount to increase ``state.start_index`` at ``epoch``.
     """
-    return get_committee_count(state, epoch)
+    return get_committees_per_slot(state, compute_start_slot_of_epoch(epoch)) * SLOTS_PER_EPOCH
 ```
 
 #### `get_beacon_proposer_index`
@@ -1547,6 +1546,12 @@ def process_attester_slashing(state: BeaconState, attester_slashing: AttesterSla
 def process_attestation(state: BeaconState, attestation: Attestation) -> None:
     data = attestation.data
     assert data.index < MAX_COMMITTEES_PER_SLOT
+    slot_start_index = get_slot_start_index(state, data.slot)
+    if data.index < slot_start_index:
+        test_index = data.index + MAX_COMMITTEES_PER_SLOT
+    else:
+        test_index = data.index
+    assert slot_start_index <= test_index < slot_start_index + get_committees_per_slot(state, data.slot)
     assert data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))
 
     assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot <= data.slot + SLOTS_PER_EPOCH

specs/validator/0_beacon-chain-validator.md

@@ -150,7 +150,7 @@ def get_committee_assignment(state: BeaconState,
     start_slot = compute_start_slot_of_epoch(epoch)
     for slot in range(start_slot, start_slot + SLOTS_PER_EPOCH):
         slot_start_index = get_slot_start_index(state, Slot(slot))
-        for i in range(get_committee_count(state, epoch) // SLOTS_PER_EPOCH):
+        for i in range(get_committees_per_slot(state, Slot(slot))):
             index = (slot_start_index + i) % MAX_COMMITTEES_PER_SLOT
             committee = get_crosslink_committee(state, Slot(slot), index)
             if validator_index in committee:

test_libs/pyspec/eth2spec/test/helpers/attestations.py

@@ -43,9 +43,6 @@ def get_valid_attestation(spec, state, slot=None, index=None, signed=False):
         slot = state.slot
     if index is None:
         index = spec.get_slot_start_index(state, slot)
-    print(slot)
-    print(index)
-    print(spec.get_committee_count(state, spec.compute_epoch_of_slot(slot)))
 
     attestation_data = build_attestation_data(spec, state, slot, index)
 

test_libs/pyspec/eth2spec/test/helpers/state.py

@@ -51,8 +51,8 @@ def next_epoch_with_attestations(spec,
     for _ in range(spec.SLOTS_PER_EPOCH):
         block = build_empty_block_for_next_slot(spec, post_state)
         if fill_cur_epoch and post_state.slot >= spec.MIN_ATTESTATION_INCLUSION_DELAY:
-            committees_per_slot = spec.get_committee_count(state, spec.get_current_epoch(state)) // spec.SLOTS_PER_EPOCH
             slot_to_attest = post_state.slot - spec.MIN_ATTESTATION_INCLUSION_DELAY + 1
+            committees_per_slot = spec.get_committees_per_slot(state, slot_to_attest)
             if slot_to_attest >= spec.compute_start_slot_of_epoch(spec.get_current_epoch(post_state)):
                 slot_start_index = spec.get_slot_start_index(state, slot_to_attest)
                 for i in range(committees_per_slot):
@@ -61,8 +61,8 @@ def next_epoch_with_attestations(spec,
                     block.body.attestations.append(cur_attestation)
 
         if fill_prev_epoch:
-            committees_per_slot = spec.get_committee_count(state, spec.get_previous_epoch(state)) // spec.SLOTS_PER_EPOCH
             slot_to_attest = post_state.slot - spec.SLOTS_PER_EPOCH + 1
+            committees_per_slot = spec.get_committees_per_slot(state, slot_to_attest)
             slot_start_index = spec.get_slot_start_index(state, slot_to_attest)
             for i in range(committees_per_slot):
                 index = (slot_start_index + i) % spec.MAX_COMMITTEES_PER_SLOT

test_libs/pyspec/eth2spec/test/phase_0/block_processing/test_process_attestation.py

@@ -124,8 +124,31 @@ def test_old_source_epoch(spec, state):
 
 @with_all_phases
 @spec_state_test
-def test_wrong_index(spec, state):
+@always_bls
-    pass
+def test_wrong_index_for_committee_signature(spec, state):
+    attestation = get_valid_attestation(spec, state)
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    attestation.data.index += 1
+
+    yield from run_attestation_processing(spec, state, attestation, False)
+
+
+@with_all_phases
+@spec_state_test
+@never_bls
+def test_wrong_index_for_slot(spec, state):
+    committees_per_slot = spec.get_committees_per_slot(state, state.slot)
+    assert committees_per_slot < spec.MAX_COMMITTEES_PER_SLOT
+    slot_start_index = spec.get_slot_start_index(state, state.slot)
+    index = slot_start_index + committees_per_slot
+
+    attestation = get_valid_attestation(spec, state)
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    attestation.data.index = index
+
+    yield from run_attestation_processing(spec, state, attestation, False)
 
 
 @with_all_phases

test_libs/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_justification_and_finalization.py

@@ -26,8 +26,8 @@ def add_mock_attestations(spec, state, epoch, source, target, sufficient_support
     remaining_balance = total_balance * 2 // 3
 
     start_slot = spec.compute_start_slot_of_epoch(epoch)
-    committees_per_slot = spec.get_committee_count(state, epoch) // spec.SLOTS_PER_EPOCH
     for slot in range(start_slot, start_slot + spec.SLOTS_PER_EPOCH):
+        committees_per_slot = spec.get_committees_per_slot(state, slot)
         slot_start_index = spec.get_slot_start_index(state, slot)
         for i in range(committees_per_slot):
             index = (slot_start_index + i) % spec.MAX_COMMITTEES_PER_SLOT