From 786e611c71d5c62bf30c988c692ab88d1a54d8f3 Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 12:05:32 +0100
Subject: [PATCH 01/22] Flags to BitVector

---
 specs/altair/beacon-chain.md | 31 +++++--------------------------
 1 file changed, 5 insertions(+), 26 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 7bf0c2d99..66b069cc5 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -69,7 +69,7 @@ Altair is the first beacon chain hard fork. Its main features are:
 
 | Name | SSZ equivalent | Description |
 | - | - | - |
-| `ParticipationFlags` | `uint8` | a succinct representation of 8 boolean participation flags |
+| `ParticipationFlags` | `BitVector[PARTICIPATION_FLAGS_LENGTH]` | a succinct representation of up to 8 boolean participation flags |
 
 ## Constants
 
@@ -99,6 +99,7 @@ Altair is the first beacon chain hard fork. Its main features are:
 | Name | Value |
 | - | - |
 | `G2_POINT_AT_INFINITY` | `BLSSignature(b'\xc0' + b'\x00' * 95)` |
+| `PARTICIPATION_FLAGS_LENGTH` | `8` |
 
 ## Configuration
 
@@ -247,28 +248,6 @@ def get_flag_indices_and_weights() -> Sequence[Tuple[int, uint64]]:
     )
 ```
 
-#### `add_flag`
-
-```python
-def add_flag(flags: ParticipationFlags, flag_index: int) -> ParticipationFlags:
-    """
-    Return a new ``ParticipationFlags`` adding ``flag_index`` to ``flags``.
-    """
-    flag = ParticipationFlags(2**flag_index)
-    return flags | flag
-```
-
-#### `has_flag`
-
-```python
-def has_flag(flags: ParticipationFlags, flag_index: int) -> bool:
-    """
-    Return whether ``flags`` has ``flag_index`` set.
-    """
-    flag = ParticipationFlags(2**flag_index)
-    return flags & flag == flag
-```
-
 ### Beacon state accessors
 
 #### `get_sync_committee_indices`
@@ -348,7 +327,7 @@ def get_unslashed_participating_indices(state: BeaconState, flag_index: int, epo
     else:
         epoch_participation = state.previous_epoch_participation
     active_validator_indices = get_active_validator_indices(state, epoch)
-    participating_indices = [i for i in active_validator_indices if has_flag(epoch_participation[i], flag_index)]
+    participating_indices = [i for i in active_validator_indices if epoch_participation[i][flag_index]]
     return set(filter(lambda index: not state.validators[index].slashed, participating_indices))
 ```
 
@@ -492,8 +471,8 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
     proposer_reward_numerator = 0
     for index in get_attesting_indices(state, data, attestation.aggregation_bits):
         for flag_index, weight in get_flag_indices_and_weights():
-            if flag_index in participation_flag_indices and not has_flag(epoch_participation[index], flag_index):
-                epoch_participation[index] = add_flag(epoch_participation[index], flag_index)
+            if flag_index in participation_flag_indices and not epoch_participation[index][flag_index]:
+                epoch_participation[index][flag_index] = True
                 proposer_reward_numerator += get_base_reward(state, index) * weight
 
     # Reward proposer

From df6bd1b6c33833c264561da361436453e5e55f4c Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 12:26:37 +0100
Subject: [PATCH 02/22] BitVector -> Bitvector

---
 specs/altair/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 66b069cc5..e023db1f7 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -69,7 +69,7 @@ Altair is the first beacon chain hard fork. Its main features are:
 
 | Name | SSZ equivalent | Description |
 | - | - | - |
-| `ParticipationFlags` | `BitVector[PARTICIPATION_FLAGS_LENGTH]` | a succinct representation of up to 8 boolean participation flags |
+| `ParticipationFlags` | `Bitvector[PARTICIPATION_FLAGS_LENGTH]` | a succinct representation of up to 8 boolean participation flags |
 
 ## Constants
 

From 238a9b03fc794bfe322ebec4b67290df4159891c Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 18:09:36 +0100
Subject: [PATCH 03/22] Correct confusing comments in
 "get_sync_committee_indices"

---
 specs/altair/beacon-chain.md | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index e023db1f7..719f93033 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -205,6 +205,7 @@ class BeaconState(Container):
 ```python
 class SyncAggregate(Container):
     sync_committee_bits: Bitvector[SYNC_COMMITTEE_SIZE]
+    # TODO! Need multiple signatures as discussed between Justin and Vitalik May 3 2021 (see Telegram)
     sync_committee_signature: BLSSignature
 ```
 
@@ -255,8 +256,9 @@ def get_flag_indices_and_weights() -> Sequence[Tuple[int, uint64]]:
 ```python
 def get_sync_committee_indices(state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
     """
-    Return the sequence of sync committee indices (which may include duplicate indices)
+    Return the sequence of sync committee indices
     for a given ``state`` and ``epoch``.
+    Can contain duplicate indices for small validator sets (< 2 * SYNC_COMMITTEE_SIZE)
     """
     MAX_RANDOM_BYTE = 2**8 - 1
     base_epoch = Epoch((max(epoch // EPOCHS_PER_SYNC_COMMITTEE_PERIOD, 1) - 1) * EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
@@ -270,7 +272,7 @@ def get_sync_committee_indices(state: BeaconState, epoch: Epoch) -> Sequence[Val
         candidate_index = active_validator_indices[shuffled_index]
         random_byte = hash(seed + uint_to_bytes(uint64(i // 32)))[i % 32]
         effective_balance = state.validators[candidate_index].effective_balance
-        if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte:  # Sample with replacement
+        if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte:
             sync_committee_indices.append(candidate_index)
         i += 1
     return sync_committee_indices

From a382cf6d5c97409868a3da558351522b8b710d95 Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 20:04:06 +0100
Subject: [PATCH 04/22] Refactor participation flag list

---
 specs/altair/beacon-chain.md | 34 ++++++++++------------------------
 1 file changed, 10 insertions(+), 24 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 719f93033..e311734d9 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -100,6 +100,9 @@ Altair is the first beacon chain hard fork. Its main features are:
 | - | - |
 | `G2_POINT_AT_INFINITY` | `BLSSignature(b'\xc0' + b'\x00' * 95)` |
 | `PARTICIPATION_FLAGS_LENGTH` | `8` |
+| `PARTICIPATION_FLAGS` | `3` |
+| `TIMELY_HEAD_WEIGHT` | `uint64(12)` |
+| `PARTICIPATION_FLAG_WEIGHTS` | `[TIMELY_HEAD_WEIGHT, TIMELY_SOURCE_WEIGHT, TIMELY_TARGET_WEIGHT]` |
 
 ## Configuration
 
@@ -233,22 +236,6 @@ def eth2_fast_aggregate_verify(pubkeys: Sequence[BLSPubkey], message: Bytes32, s
     return bls.FastAggregateVerify(pubkeys, message, signature)
 ```
 
-### Misc
-
-#### `get_flag_indices_and_weights`
-
-```python
-def get_flag_indices_and_weights() -> Sequence[Tuple[int, uint64]]:
-    """
-    Return paired tuples of participation flag indices along with associated incentivization weights.
-    """
-    return (
-        (TIMELY_HEAD_FLAG_INDEX, TIMELY_HEAD_WEIGHT),
-        (TIMELY_SOURCE_FLAG_INDEX, TIMELY_SOURCE_WEIGHT),
-        (TIMELY_TARGET_FLAG_INDEX, TIMELY_TARGET_WEIGHT),
-    )
-```
-
 ### Beacon state accessors
 
 #### `get_sync_committee_indices`
@@ -336,16 +323,16 @@ def get_unslashed_participating_indices(state: BeaconState, flag_index: int, epo
 #### `get_flag_index_deltas`
 
 ```python
-def get_flag_index_deltas(state: BeaconState, flag_index: int, weight: uint64) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
+def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
     """
     Return the deltas for a given ``flag_index`` scaled by ``weight`` by scanning through the participation flags.
     """
     rewards = [Gwei(0)] * len(state.validators)
     penalties = [Gwei(0)] * len(state.validators)
     unslashed_participating_indices = get_unslashed_participating_indices(state, flag_index, get_previous_epoch(state))
-    increment = EFFECTIVE_BALANCE_INCREMENT  # Factored out from balances to avoid uint64 overflow
-    unslashed_participating_increments = get_total_balance(state, unslashed_participating_indices) // increment
-    active_increments = get_total_active_balance(state) // increment
+    weight = PARTICIPATION_FLAG_WEIGHTS[flag_index]
+    unslashed_participating_increments = get_total_balance(state, unslashed_participating_indices) // EFFECTIVE_BALANCE_INCREMENT
+    active_increments = get_total_active_balance(state) // EFFECTIVE_BALANCE_INCREMENT
     for index in get_eligible_validator_indices(state):
         base_reward = get_base_reward(state, index)
         if index in unslashed_participating_indices:
@@ -376,7 +363,7 @@ def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], S
         previous_epoch = get_previous_epoch(state)
         matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
         for index in get_eligible_validator_indices(state):
-            for (_, weight) in get_flag_indices_and_weights():
+            for weight in PARTICIPATION_FLAG_WEIGHTS:
                 # This inactivity penalty cancels the flag reward corresponding to the flag index
                 penalties[index] += Gwei(get_base_reward(state, index) * weight // WEIGHT_DENOMINATOR)
             if index not in matching_target_indices:
@@ -472,7 +459,7 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
     # Update epoch participation flags
     proposer_reward_numerator = 0
     for index in get_attesting_indices(state, data, attestation.aggregation_bits):
-        for flag_index, weight in get_flag_indices_and_weights():
+        for flag_index, weight in enumerate(PARTICIPATION_FLAG_WEIGHTS):
             if flag_index in participation_flag_indices and not epoch_participation[index][flag_index]:
                 epoch_participation[index][flag_index] = True
                 proposer_reward_numerator += get_base_reward(state, index) * weight
@@ -613,8 +600,7 @@ def process_rewards_and_penalties(state: BeaconState) -> None:
     if get_current_epoch(state) == GENESIS_EPOCH:
         return
 
-    flag_indices_and_numerators = get_flag_indices_and_weights()
-    flag_deltas = [get_flag_index_deltas(state, index, numerator) for (index, numerator) in flag_indices_and_numerators]
+    flag_deltas = [get_flag_index_deltas(state, flag_index) for flag_index in range(PARTICIPATION_FLAGS)]
     deltas = flag_deltas + [get_inactivity_penalty_deltas(state)]
     for (rewards, penalties) in deltas:
         for index in range(len(state.validators)):

From 227d1007e67558e7b7a419723efe932470976441 Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 20:09:14 +0100
Subject: [PATCH 05/22] Update toc

---
 specs/altair/beacon-chain.md | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index e311734d9..bd9c23bf3 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -27,10 +27,6 @@
 - [Helper functions](#helper-functions)
   - [`Predicates`](#predicates)
     - [`eth2_fast_aggregate_verify`](#eth2_fast_aggregate_verify)
-  - [Misc](#misc-2)
-    - [`get_flag_indices_and_weights`](#get_flag_indices_and_weights)
-    - [`add_flag`](#add_flag)
-    - [`has_flag`](#has_flag)
   - [Beacon state accessors](#beacon-state-accessors)
     - [`get_sync_committee_indices`](#get_sync_committee_indices)
     - [`get_sync_committee`](#get_sync_committee)

From 687641a79bbe9db18de358f6c230e05a59cb905e Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 21:55:36 +0100
Subject: [PATCH 06/22] Remove extra variable

---
 specs/altair/beacon-chain.md | 1 -
 1 file changed, 1 deletion(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index bd9c23bf3..1a50e7337 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -97,7 +97,6 @@ Altair is the first beacon chain hard fork. Its main features are:
 | `G2_POINT_AT_INFINITY` | `BLSSignature(b'\xc0' + b'\x00' * 95)` |
 | `PARTICIPATION_FLAGS_LENGTH` | `8` |
 | `PARTICIPATION_FLAGS` | `3` |
-| `TIMELY_HEAD_WEIGHT` | `uint64(12)` |
 | `PARTICIPATION_FLAG_WEIGHTS` | `[TIMELY_HEAD_WEIGHT, TIMELY_SOURCE_WEIGHT, TIMELY_TARGET_WEIGHT]` |
 
 ## Configuration

From 55471bc5d4f69678baf6950e6197b5206b2cbb8a Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 21:58:03 +0100
Subject: [PATCH 07/22] Revert "BitVector -> Bitvector"

This reverts commit df6bd1b6c33833c264561da361436453e5e55f4c.
---
 specs/altair/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 1a50e7337..9e868fbaa 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -65,7 +65,7 @@ Altair is the first beacon chain hard fork. Its main features are:
 
 | Name | SSZ equivalent | Description |
 | - | - | - |
-| `ParticipationFlags` | `Bitvector[PARTICIPATION_FLAGS_LENGTH]` | a succinct representation of up to 8 boolean participation flags |
+| `ParticipationFlags` | `BitVector[PARTICIPATION_FLAGS_LENGTH]` | a succinct representation of up to 8 boolean participation flags |
 
 ## Constants
 

From 77524036f56c71d4c8199c1393af524b7841290f Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 22:02:37 +0100
Subject: [PATCH 08/22] Revert "Flags to BitVector"

This reverts commit 786e611c71d5c62bf30c988c692ab88d1a54d8f3.

# Conflicts:
#	specs/altair/beacon-chain.md
---
 specs/altair/beacon-chain.md | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 9e868fbaa..5bce9ba4e 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -27,6 +27,9 @@
 - [Helper functions](#helper-functions)
   - [`Predicates`](#predicates)
     - [`eth2_fast_aggregate_verify`](#eth2_fast_aggregate_verify)
+  - [Misc](#misc-2)
+    - [`add_flag`](#add_flag)
+    - [`has_flag`](#has_flag)
   - [Beacon state accessors](#beacon-state-accessors)
     - [`get_sync_committee_indices`](#get_sync_committee_indices)
     - [`get_sync_committee`](#get_sync_committee)
@@ -65,7 +68,7 @@ Altair is the first beacon chain hard fork. Its main features are:
 
 | Name | SSZ equivalent | Description |
 | - | - | - |
-| `ParticipationFlags` | `BitVector[PARTICIPATION_FLAGS_LENGTH]` | a succinct representation of up to 8 boolean participation flags |
+| `ParticipationFlags` | `uint8` | a succinct representation of 8 boolean participation flags |
 
 ## Constants
 
@@ -95,7 +98,6 @@ Altair is the first beacon chain hard fork. Its main features are:
 | Name | Value |
 | - | - |
 | `G2_POINT_AT_INFINITY` | `BLSSignature(b'\xc0' + b'\x00' * 95)` |
-| `PARTICIPATION_FLAGS_LENGTH` | `8` |
 | `PARTICIPATION_FLAGS` | `3` |
 | `PARTICIPATION_FLAG_WEIGHTS` | `[TIMELY_HEAD_WEIGHT, TIMELY_SOURCE_WEIGHT, TIMELY_TARGET_WEIGHT]` |
 
@@ -231,6 +233,30 @@ def eth2_fast_aggregate_verify(pubkeys: Sequence[BLSPubkey], message: Bytes32, s
     return bls.FastAggregateVerify(pubkeys, message, signature)
 ```
 
+### Misc
+
+#### `add_flag`
+
+```python
+def add_flag(flags: ParticipationFlags, flag_index: int) -> ParticipationFlags:
+    """
+    Return a new ``ParticipationFlags`` adding ``flag_index`` to ``flags``.
+    """
+    flag = ParticipationFlags(2**flag_index)
+    return flags | flag
+```
+
+#### `has_flag`
+
+```python
+def has_flag(flags: ParticipationFlags, flag_index: int) -> bool:
+    """
+    Return whether ``flags`` has ``flag_index`` set.
+    """
+    flag = ParticipationFlags(2**flag_index)
+    return flags & flag == flag
+```
+
 ### Beacon state accessors
 
 #### `get_sync_committee_indices`
@@ -311,7 +337,7 @@ def get_unslashed_participating_indices(state: BeaconState, flag_index: int, epo
     else:
         epoch_participation = state.previous_epoch_participation
     active_validator_indices = get_active_validator_indices(state, epoch)
-    participating_indices = [i for i in active_validator_indices if epoch_participation[i][flag_index]]
+    participating_indices = [i for i in active_validator_indices if has_flag(epoch_participation[i], flag_index)]
     return set(filter(lambda index: not state.validators[index].slashed, participating_indices))
 ```
 

From b041a9b0d68cdee2de0d0d36590f07b49ea12dff Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Wed, 5 May 2021 22:22:32 +0100
Subject: [PATCH 09/22] Further flag_index revert

---
 specs/altair/beacon-chain.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 5bce9ba4e..5a8dcce24 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -481,8 +481,8 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
     proposer_reward_numerator = 0
     for index in get_attesting_indices(state, data, attestation.aggregation_bits):
         for flag_index, weight in enumerate(PARTICIPATION_FLAG_WEIGHTS):
-            if flag_index in participation_flag_indices and not epoch_participation[index][flag_index]:
-                epoch_participation[index][flag_index] = True
+            if flag_index in participation_flag_indices and not has_flag(epoch_participation[index], flag_index):
+                epoch_participation[index] = add_flag(epoch_participation[index], flag_index)
                 proposer_reward_numerator += get_base_reward(state, index) * weight
 
     # Reward proposer

From cbf9f85537c3c91c38ac51b1e3ac4efd2d5f240c Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Thu, 6 May 2021 12:28:18 +0100
Subject: [PATCH 10/22] Remove duplicate inactivity leak

---
 specs/altair/beacon-chain.md | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 5a8dcce24..9ad2c0089 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -357,10 +357,7 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
     for index in get_eligible_validator_indices(state):
         base_reward = get_base_reward(state, index)
         if index in unslashed_participating_indices:
-            if is_in_inactivity_leak(state):
-                # This flag reward cancels the inactivity penalty corresponding to the flag index
-                rewards[index] += Gwei(base_reward * weight // WEIGHT_DENOMINATOR)
-            else:
+            if not is_in_inactivity_leak(state):
                 reward_numerator = base_reward * weight * unslashed_participating_increments
                 rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
         else:
@@ -384,9 +381,6 @@ def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], S
         previous_epoch = get_previous_epoch(state)
         matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
         for index in get_eligible_validator_indices(state):
-            for weight in PARTICIPATION_FLAG_WEIGHTS:
-                # This inactivity penalty cancels the flag reward corresponding to the flag index
-                penalties[index] += Gwei(get_base_reward(state, index) * weight // WEIGHT_DENOMINATOR)
             if index not in matching_target_indices:
                 penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
                 penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR

From cf724daa7a07092a02522879a0b1cb088db7c3b5 Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Thu, 6 May 2021 12:42:05 +0100
Subject: [PATCH 11/22] No inactivity penalty for untimely head

---
 specs/altair/beacon-chain.md | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 9ad2c0089..e90c587be 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -354,13 +354,14 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
     weight = PARTICIPATION_FLAG_WEIGHTS[flag_index]
     unslashed_participating_increments = get_total_balance(state, unslashed_participating_indices) // EFFECTIVE_BALANCE_INCREMENT
     active_increments = get_total_active_balance(state) // EFFECTIVE_BALANCE_INCREMENT
+    in_inactivity_leak = is_in_inactivity_leak(state)
     for index in get_eligible_validator_indices(state):
         base_reward = get_base_reward(state, index)
         if index in unslashed_participating_indices:
-            if not is_in_inactivity_leak(state):
+            if not in_inactivity_leak:
                 reward_numerator = base_reward * weight * unslashed_participating_increments
                 rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
-        else:
+        elif not (in_inactivity_leak and flag_index == TIMELY_HEAD_FLAG_INDEX):
             penalties[index] += Gwei(base_reward * weight // WEIGHT_DENOMINATOR)
     return rewards, penalties
 ```

From 81a8c2748fed22b6b5753840f228f00b212c8072 Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Thu, 6 May 2021 13:03:26 +0100
Subject: [PATCH 12/22] Integrate get_inactivity_penalty_deltas into reward
 computation for better readability

---
 specs/altair/beacon-chain.md | 34 ++++++++--------------------------
 1 file changed, 8 insertions(+), 26 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index e90c587be..f464bd640 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -350,7 +350,8 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
     """
     rewards = [Gwei(0)] * len(state.validators)
     penalties = [Gwei(0)] * len(state.validators)
-    unslashed_participating_indices = get_unslashed_participating_indices(state, flag_index, get_previous_epoch(state))
+    previous_epoch = get_previous_epoch(state)
+    unslashed_participating_indices = get_unslashed_participating_indices(state, flag_index, previous_epoch)
     weight = PARTICIPATION_FLAG_WEIGHTS[flag_index]
     unslashed_participating_increments = get_total_balance(state, unslashed_participating_indices) // EFFECTIVE_BALANCE_INCREMENT
     active_increments = get_total_active_balance(state) // EFFECTIVE_BALANCE_INCREMENT
@@ -363,29 +364,11 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
                 rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
         elif not (in_inactivity_leak and flag_index == TIMELY_HEAD_FLAG_INDEX):
             penalties[index] += Gwei(base_reward * weight // WEIGHT_DENOMINATOR)
-    return rewards, penalties
-```
-
-#### Modified `get_inactivity_penalty_deltas`
-
-*Note*: The function `get_inactivity_penalty_deltas` is modified in the selection of matching target indices
-and the removal of `BASE_REWARDS_PER_EPOCH`.
-
-```python
-def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
-    """
-    Return the inactivity penalty deltas by considering timely target participation flags and inactivity scores.
-    """
-    rewards = [Gwei(0) for _ in range(len(state.validators))]
-    penalties = [Gwei(0) for _ in range(len(state.validators))]
-    if is_in_inactivity_leak(state):
-        previous_epoch = get_previous_epoch(state)
-        matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
-        for index in get_eligible_validator_indices(state):
-            if index not in matching_target_indices:
-                penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
-                penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR
-                penalties[index] += Gwei(penalty_numerator // penalty_denominator)
+        # Quadratic inactivity leak
+        if flag_index == TIMELY_TARGET_FLAG_INDEX and in_inactivity_leak and index not in unslashed_participating_indices:
+            penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
+            penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR
+            penalties[index] += Gwei(penalty_numerator // penalty_denominator)
     return rewards, penalties
 ```
 
@@ -617,8 +600,7 @@ def process_rewards_and_penalties(state: BeaconState) -> None:
         return
 
     flag_deltas = [get_flag_index_deltas(state, flag_index) for flag_index in range(PARTICIPATION_FLAGS)]
-    deltas = flag_deltas + [get_inactivity_penalty_deltas(state)]
-    for (rewards, penalties) in deltas:
+    for (rewards, penalties) in flag_deltas:
         for index in range(len(state.validators)):
             increase_balance(state, ValidatorIndex(index), rewards[index])
             decrease_balance(state, ValidatorIndex(index), penalties[index])

From ba2c717bf112bb496afc80cedbd1aeac7d59049a Mon Sep 17 00:00:00 2001
From: Dankrad Feist <mail@dankradfeist.de>
Date: Thu, 6 May 2021 22:55:17 +0100
Subject: [PATCH 13/22] Remove PARTICIPATION_FLAGS

---
 specs/altair/beacon-chain.md | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index f464bd640..f559a55ef 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -98,7 +98,6 @@ Altair is the first beacon chain hard fork. Its main features are:
 | Name | Value |
 | - | - |
 | `G2_POINT_AT_INFINITY` | `BLSSignature(b'\xc0' + b'\x00' * 95)` |
-| `PARTICIPATION_FLAGS` | `3` |
 | `PARTICIPATION_FLAG_WEIGHTS` | `[TIMELY_HEAD_WEIGHT, TIMELY_SOURCE_WEIGHT, TIMELY_TARGET_WEIGHT]` |
 
 ## Configuration
@@ -599,7 +598,7 @@ def process_rewards_and_penalties(state: BeaconState) -> None:
     if get_current_epoch(state) == GENESIS_EPOCH:
         return
 
-    flag_deltas = [get_flag_index_deltas(state, flag_index) for flag_index in range(PARTICIPATION_FLAGS)]
+    flag_deltas = [get_flag_index_deltas(state, flag_index) for flag_index in range(len(PARTICIPATION_FLAG_WEIGHTS))]
     for (rewards, penalties) in flag_deltas:
         for index in range(len(state.validators)):
             increase_balance(state, ValidatorIndex(index), rewards[index])

From 2fc68c451e8168b2c2cc85182e77e41550c15302 Mon Sep 17 00:00:00 2001
From: dankrad <dankrad@ethereum.org>
Date: Thu, 6 May 2021 22:55:55 +0100
Subject: [PATCH 14/22] Update specs/altair/beacon-chain.md

Co-authored-by: Alex Stokes <r.alex.stokes@gmail.com>
---
 specs/altair/beacon-chain.md | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index f559a55ef..f21584f30 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -263,8 +263,7 @@ def has_flag(flags: ParticipationFlags, flag_index: int) -> bool:
 ```python
 def get_sync_committee_indices(state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
     """
-    Return the sequence of sync committee indices
-    for a given ``state`` and ``epoch``.
+    Return the sequence of sync committee indices for a given ``state`` and ``epoch``.
     Can contain duplicate indices for small validator sets (< 2 * SYNC_COMMITTEE_SIZE)
     """
     MAX_RANDOM_BYTE = 2**8 - 1

From cd7842557054845462e2f209751c8f61d14c0111 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Mon, 10 May 2021 10:30:47 -0600
Subject: [PATCH 15/22] lint

---
 specs/altair/beacon-chain.md | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 5c21573fb..5a4b37a83 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -362,19 +362,22 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
     previous_epoch = get_previous_epoch(state)
     unslashed_participating_indices = get_unslashed_participating_indices(state, flag_index, previous_epoch)
     weight = PARTICIPATION_FLAG_WEIGHTS[flag_index]
-    unslashed_participating_increments = get_total_balance(state, unslashed_participating_indices) // EFFECTIVE_BALANCE_INCREMENT
+    unslashed_participating_balance = get_total_balance(state, unslashed_participating_indices)
+    unslashed_participating_increments = unslashed_participating_balance // EFFECTIVE_BALANCE_INCREMENT
     active_increments = get_total_active_balance(state) // EFFECTIVE_BALANCE_INCREMENT
     in_inactivity_leak = is_in_inactivity_leak(state)
     for index in get_eligible_validator_indices(state):
         base_reward = get_base_reward(state, index)
-        if index in unslashed_participating_indices:
+        index_participated = index in unslashed_participating_indices
+        if index_participated:
             if not in_inactivity_leak:
                 reward_numerator = base_reward * weight * unslashed_participating_increments
                 rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
         elif not (in_inactivity_leak and flag_index == TIMELY_HEAD_FLAG_INDEX):
             penalties[index] += Gwei(base_reward * weight // WEIGHT_DENOMINATOR)
+
         # Quadratic inactivity leak
-        if flag_index == TIMELY_TARGET_FLAG_INDEX and in_inactivity_leak and index not in unslashed_participating_indices:
+        if flag_index == TIMELY_TARGET_FLAG_INDEX and in_inactivity_leak and index_participated:
             penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
             penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR
             penalties[index] += Gwei(penalty_numerator // penalty_denominator)

From 1494fe6ace0c54231d8e7d080da7eb5134a829df Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Mon, 10 May 2021 10:59:33 -0600
Subject: [PATCH 16/22] add get_inactivity_penalty_deltas back in

---
 specs/altair/beacon-chain.md | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 5a4b37a83..265bbfa53 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -37,6 +37,7 @@
     - [`get_base_reward`](#get_base_reward)
     - [`get_unslashed_participating_indices`](#get_unslashed_participating_indices)
     - [`get_flag_index_deltas`](#get_flag_index_deltas)
+    - [Modified `get_inactivity_penalty_deltas`](#modified-get_inactivity_penalty_deltas)
   - [Beacon state mutators](#beacon-state-mutators)
     - [Modified `slash_validator`](#modified-slash_validator)
   - [Block processing](#block-processing)
@@ -368,19 +369,32 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
     in_inactivity_leak = is_in_inactivity_leak(state)
     for index in get_eligible_validator_indices(state):
         base_reward = get_base_reward(state, index)
-        index_participated = index in unslashed_participating_indices
-        if index_participated:
+        if index in unslashed_participating_indices:
             if not in_inactivity_leak:
                 reward_numerator = base_reward * weight * unslashed_participating_increments
                 rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
-        elif not (in_inactivity_leak and flag_index == TIMELY_HEAD_FLAG_INDEX):
+        else:
             penalties[index] += Gwei(base_reward * weight // WEIGHT_DENOMINATOR)
+    return rewards, penalties
+```
 
-        # Quadratic inactivity leak
-        if flag_index == TIMELY_TARGET_FLAG_INDEX and in_inactivity_leak and index_participated:
-            penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
-            penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR
-            penalties[index] += Gwei(penalty_numerator // penalty_denominator)
+#### Modified `get_inactivity_penalty_deltas`
+
+```python
+def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
+    """
+    Return the inactivity penalty deltas by considering timely target participation flags and inactivity scores.
+    """
+    rewards = [Gwei(0) for _ in range(len(state.validators))]
+    penalties = [Gwei(0) for _ in range(len(state.validators))]
+    if is_in_inactivity_leak(state):
+        previous_epoch = get_previous_epoch(state)
+        matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
+        for index in get_eligible_validator_indices(state):
+            if index not in matching_target_indices:
+                penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
+                penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR
+                penalties[index] += Gwei(penalty_numerator // penalty_denominator)
     return rewards, penalties
 ```
 
@@ -613,7 +627,8 @@ def process_rewards_and_penalties(state: BeaconState) -> None:
         return
 
     flag_deltas = [get_flag_index_deltas(state, flag_index) for flag_index in range(len(PARTICIPATION_FLAG_WEIGHTS))]
-    for (rewards, penalties) in flag_deltas:
+    deltas = flag_deltas + [get_inactivity_penalty_deltas(state)]
+    for (rewards, penalties) in deltas:
         for index in range(len(state.validators)):
             increase_balance(state, ValidatorIndex(index), rewards[index])
             decrease_balance(state, ValidatorIndex(index), penalties[index])

From 77d607a760865d9dd621da5b1f3e39dfe0e7161e Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Mon, 10 May 2021 13:24:14 -0600
Subject: [PATCH 17/22] fix test

---
 tests/core/pyspec/eth2spec/test/helpers/rewards.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/core/pyspec/eth2spec/test/helpers/rewards.py b/tests/core/pyspec/eth2spec/test/helpers/rewards.py
index f81c1fc2a..7cf0206b3 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/rewards.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/rewards.py
@@ -62,13 +62,13 @@ def run_deltas(spec, state):
 
     if is_post_altair(spec):
         def get_source_deltas(state):
-            return spec.get_flag_index_deltas(state, spec.TIMELY_SOURCE_FLAG_INDEX, spec.TIMELY_SOURCE_WEIGHT)
+            return spec.get_flag_index_deltas(state, spec.TIMELY_SOURCE_FLAG_INDEX)
 
         def get_head_deltas(state):
-            return spec.get_flag_index_deltas(state, spec.TIMELY_HEAD_FLAG_INDEX, spec.TIMELY_HEAD_WEIGHT)
+            return spec.get_flag_index_deltas(state, spec.TIMELY_HEAD_FLAG_INDEX)
 
         def get_target_deltas(state):
-            return spec.get_flag_index_deltas(state, spec.TIMELY_TARGET_FLAG_INDEX, spec.TIMELY_TARGET_WEIGHT)
+            return spec.get_flag_index_deltas(state, spec.TIMELY_TARGET_FLAG_INDEX)
 
     yield from run_attestation_component_deltas(
         spec,
@@ -228,7 +228,7 @@ def run_get_inactivity_penalty_deltas(spec, state):
             else:
                 base_penalty = sum(
                     base_reward * numerator // spec.WEIGHT_DENOMINATOR
-                    for (_, numerator) in spec.get_flag_indices_and_weights()
+                    for (_, numerator) in spec.PARTICIPATION_FLAG_WEIGHTS
                 )
 
             if not has_enough_for_reward(spec, state, index):

From a6b8574962dc03f6f36b56a744f3542e97ffeed8 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Mon, 10 May 2021 13:38:45 -0600
Subject: [PATCH 18/22] test

---
 specs/altair/beacon-chain.md                  |  3 +-
 .../pyspec/eth2spec/test/helpers/rewards.py   | 28 ++++++++++++-------
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 265bbfa53..90b878cc1 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -366,11 +366,10 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
     unslashed_participating_balance = get_total_balance(state, unslashed_participating_indices)
     unslashed_participating_increments = unslashed_participating_balance // EFFECTIVE_BALANCE_INCREMENT
     active_increments = get_total_active_balance(state) // EFFECTIVE_BALANCE_INCREMENT
-    in_inactivity_leak = is_in_inactivity_leak(state)
     for index in get_eligible_validator_indices(state):
         base_reward = get_base_reward(state, index)
         if index in unslashed_participating_indices:
-            if not in_inactivity_leak:
+            if not is_in_inactivity_leak(state):
                 reward_numerator = base_reward * weight * unslashed_participating_increments
                 rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
         else:
diff --git a/tests/core/pyspec/eth2spec/test/helpers/rewards.py b/tests/core/pyspec/eth2spec/test/helpers/rewards.py
index 7cf0206b3..eb47dac98 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/rewards.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/rewards.py
@@ -133,10 +133,17 @@ def run_attestation_component_deltas(spec, state, component_delta_fn, matching_a
         validator = state.validators[index]
         enough_for_reward = has_enough_for_reward(spec, state, index)
         if index in matching_indices and not validator.slashed:
-            if enough_for_reward:
-                assert rewards[index] > 0
+            if is_post_altair(spec):
+                if not spec.is_in_inactivity_leak(state) and enough_for_reward:
+                    assert rewards[index] > 0
+                else:
+                    assert rewards[index] == 0
             else:
-                assert rewards[index] == 0
+                if enough_for_reward:
+                    assert rewards[index] > 0
+                else:
+                    assert rewards[index] == 0
+
             assert penalties[index] == 0
         else:
             assert rewards[index] == 0
@@ -225,18 +232,19 @@ def run_get_inactivity_penalty_deltas(spec, state):
             if not is_post_altair(spec):
                 cancel_base_rewards_per_epoch = spec.BASE_REWARDS_PER_EPOCH
                 base_penalty = cancel_base_rewards_per_epoch * base_reward - spec.get_proposer_reward(state, index)
-            else:
-                base_penalty = sum(
-                    base_reward * numerator // spec.WEIGHT_DENOMINATOR
-                    for (_, numerator) in spec.PARTICIPATION_FLAG_WEIGHTS
-                )
 
             if not has_enough_for_reward(spec, state, index):
                 assert penalties[index] == 0
             elif index in matching_attesting_indices or not has_enough_for_leak_penalty(spec, state, index):
-                assert penalties[index] == base_penalty
+                if is_post_altair(spec):
+                    assert penalties[index] == 0
+                else:
+                    assert penalties[index] == base_penalty
             else:
-                assert penalties[index] > base_penalty
+                if is_post_altair(spec):
+                    assert penalties[index] > 0
+                else:
+                    assert penalties[index] > base_penalty
         else:
             assert penalties[index] == 0
 

From a9cc036184dedde472e22a3ae9ba45db7a094695 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Tue, 11 May 2021 11:48:26 -0600
Subject: [PATCH 19/22] remove timely_head penalty

---
 specs/altair/beacon-chain.md                       | 2 +-
 tests/core/pyspec/eth2spec/test/helpers/rewards.py | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 90b878cc1..57fec33df 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -372,7 +372,7 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
             if not is_in_inactivity_leak(state):
                 reward_numerator = base_reward * weight * unslashed_participating_increments
                 rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
-        else:
+        elif not flag_index == TIMELY_HEAD_FLAG_INDEX:
             penalties[index] += Gwei(base_reward * weight // WEIGHT_DENOMINATOR)
     return rewards, penalties
 ```
diff --git a/tests/core/pyspec/eth2spec/test/helpers/rewards.py b/tests/core/pyspec/eth2spec/test/helpers/rewards.py
index eb47dac98..f563c70a2 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/rewards.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/rewards.py
@@ -147,7 +147,9 @@ def run_attestation_component_deltas(spec, state, component_delta_fn, matching_a
             assert penalties[index] == 0
         else:
             assert rewards[index] == 0
-            if enough_for_reward:
+            if is_post_altair(spec) and 'head' in deltas_name:
+                assert penalties[index] == 0
+            elif enough_for_reward:
                 assert penalties[index] > 0
             else:
                 assert penalties[index] == 0

From 09cefa03f3895c2a319ee03bc06c66a6b8d5e11b Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Tue, 11 May 2021 16:07:24 -0600
Subject: [PATCH 20/22] remov sync signature todo

---
 specs/altair/beacon-chain.md | 1 -
 1 file changed, 1 deletion(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 57fec33df..6d97c14b5 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -203,7 +203,6 @@ class BeaconState(Container):
 ```python
 class SyncAggregate(Container):
     sync_committee_bits: Bitvector[SYNC_COMMITTEE_SIZE]
-    # TODO! Need multiple signatures as discussed between Justin and Vitalik May 3 2021 (see Telegram)
     sync_committee_signature: BLSSignature
 ```
 

From 6371707779791a687886f6f7c3b2d1ebd45ae345 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 12 May 2021 08:40:34 -0600
Subject: [PATCH 21/22] Apply suggestions from code review

Co-authored-by: Hsiao-Wei Wang <hsiaowei.eth@gmail.com>
---
 specs/altair/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 6d97c14b5..9593d13a9 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -371,7 +371,7 @@ def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence
             if not is_in_inactivity_leak(state):
                 reward_numerator = base_reward * weight * unslashed_participating_increments
                 rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
-        elif not flag_index == TIMELY_HEAD_FLAG_INDEX:
+        elif flag_index != TIMELY_HEAD_FLAG_INDEX:
             penalties[index] += Gwei(base_reward * weight // WEIGHT_DENOMINATOR)
     return rewards, penalties
 ```

From 5188671816b3a846b1fa5ea781d3321f0e2c5f04 Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 12 May 2021 12:18:35 -0600
Subject: [PATCH 22/22] Update specs/altair/beacon-chain.md

Co-authored-by: dankrad <dankrad@ethereum.org>
---
 specs/altair/beacon-chain.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index 9593d13a9..492a146ea 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -262,7 +262,7 @@ def has_flag(flags: ParticipationFlags, flag_index: int) -> bool:
 def get_sync_committee_indices(state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
     """
     Return the sequence of sync committee indices for a given ``state`` and ``epoch``.
-    Note: Committee can contain duplicate indices for small validator sets (< 2 * SYNC_COMMITTEE_SIZE)
+    Note: Committee can contain duplicate indices for small validator sets (< SYNC_COMMITTEE_SIZE + 128)
 
     Note: This function is not stable during a sync committee period as
     a validator's effective balance may change enough to affect the sampling.