Agent Conversation: anthropic/claude-opus-4.6

Model: anthropic/claude-opus-4.6
Total steps: 7
Messages: 15
UserStep 0

Task: rl-value-discrete

Online RL: Value-Based Methods for Discrete Control

Objective

Design and implement a value-based RL algorithm for discrete action spaces. Your code goes in custom_value_discrete.py. Three reference implementations (DQN, DoubleDQN, C51) are provided as read-only.

Background

Value-based methods estimate Q-values Q(s,a) for each state-action pair and derive a policy by selecting actions with the highest Q-value. Key challenges include overestimation bias, sample efficiency, and representing uncertainty. Different approaches address these through double Q-learning, distributional value functions, or prioritized replay.

Constraints

  • Network architecture dimensions are FIXED and cannot be modified
  • Total parameter count is enforced at runtime
  • Focus on algorithmic innovation: new loss functions, update rules, exploration strategies, etc.
  • Do NOT simply copy a reference implementation with minor changes

Evaluation

Trained and evaluated on CartPole-v1, LunarLander-v2, Acrobot-v1. Additional held-out environments (not shown during intermediate testing) are used to assess generalization. Metric: mean episodic return over 10 evaluation episodes (higher is better).

cleanrl/cleanrl/custom_value_discrete.py [EDITABLE — lines 174–242 only]

     1: # Custom value-based discrete RL algorithm for MLS-Bench
     2: #
     3: # EDITABLE section: QNetwork head and ValueAlgorithm classes.
     4: # FIXED sections: everything else (config, env, buffer, encoder, utility, training loop).
     5: import os
     6: import random
     7: import time
     8: from dataclasses import dataclass
     9: 
    10: import gymnasium as gym
    11: import numpy as np
    12: import torch
    13: import torch.nn as nn
    14: import torch.nn.functional as F
    15: import torch.optim as optim
    16: import tyro
    17: 
    18: 
    19: # =====================================================================
    20: # FIXED: Configuration
    21: # =====================================================================
    22: @dataclass
    23: class Args:
    24:     exp_name: str = os.path.basename(__file__)[: -len(".py")]
    25:     """the name of this experiment"""
    26:     seed: int = 1
    27:     """seed of the experiment"""
    28:     torch_deterministic: bool = True
    29:     """if toggled, `torch.backends.cudnn.deterministic=False`"""
    30:     cuda: bool = True
    31:     """if toggled, cuda will be enabled by default"""
    32: 
    33:     # Algorithm specific arguments
    34:     env_id: str = "CartPole-v1"
    35:     """the id of the environment"""
    36:     total_timesteps: int = 500000
    37:     """total timesteps of the experiments"""
    38:     learning_rate: float = 2.5e-4
    39:     """the learning rate of the optimizer"""
    40:     buffer_size: int = 10000
    41:     """the replay memory buffer size"""
    42:     gamma: float = 0.99
    43:     """the discount factor gamma"""
AssistantStep 1edit
Tool Input
1{
2  "error": "Failed to parse tool arguments: Expecting ',' delimiter: line 1 column 109 (char 108)"
3}
Tool ResultStep 1
ERROR: Failed to parse tool arguments: Expecting ',' delimiter: line 1 column 109 (char 108)
AssistantStep 2edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_value_discrete.py",
4  "start_line": 174,
5  "end_line": 242,
6  "content": "class QNetwork(nn.Module):\n    \"\"\"Q-network: MLPEncoder (fixed) + head. Output: Q-values per action.\"\"\"\n\n    def __init__(self, obs_dim, n_actions):\n        super().__init__()\n        self.encoder = MLPEncoder(obs_dim)\n        self.head = nn.Linear(ENCODER_FEATURE_DIM, n_actions)\n\n    def forward(self, obs):\n        features = self.encoder(obs)\n        return self.head(features)\n\n\nclass ValueAlgorithm:\n    \"\"\"Munchausen Double DQN: entropy-augmented bootstrapping with double\n    Q-learning. Adds a scaled log-policy bonus to rewards and uses soft\n    value targets, providing implicit KL regularization. Uses the online\n    network's policy for next-state action ranking (double Q-learning)\n    while evaluating with the target network's Q-values.\n    \"\"\"\n\n    def __init__(self, obs_dim, n_actions, device, args):\n        self.device = device\n        self.n_actions = n_actions\n        self.gamma = args.gamma\n        self.total_it = 0\n        self.m_alpha = 0.9   # Munchausen scaling factor\n        self.m_tau = 0.03    # entropy temperature\n        self.lo = -1.0       # log-policy clipping lower bound\n        self.q_network = QNetwork(obs_dim, n_actions).to(device)\n        self.target_network = QNetwork(obs_dim, n_actions).to(device)\n        self.target_network.load_state_dict(self.q_network.state_dict())\n        self.optimizer = optim.Adam(self.q_network.parameters(), lr=args.learning_rate)\n\n    def select_action(self, obs, epsilon):\n        if random.random() < epsilon:\n            return random.randint(0, self.n_actions - 1)\n        obs_t = torch.tensor(obs.reshape(1, -1), device=self.device, dtype=torch.float32)\n        q_values = self.q_network(obs_t)\n        return torch.argmax(q_values, dim=1).item()\n\n    def update(self, batch, global_step):\n        self.total_it += 1\n        obs, next_obs, actions, rewards, dones = batch\n        with torch.no_grad():\n            # Double Q: use online net's policy, target net's Q-values\n            q_next_online = self.q_network(next_obs)\n            q_next_target = self.target_network(next_obs)\n            # Soft policy from online network for next state\n            log_pi_next = F.log_softmax(q_next_online / self.m_tau, dim=1)\n            pi_next = log_pi_next.exp()\n            # Soft value using target Q-values but online policy (Double)\n            v_next = (pi_next * (q_next_target - self.m_tau * log_pi_next)).sum(1)\n            # Munchausen bonus: log-policy for current action (target net)\n            q_curr_tgt = self.target_network(obs)\n            lp = F.log_softmax(q_curr_tgt / self.m_tau, dim=1)\n            lp_a = lp[torch.arange(len(obs)), actions].clamp(self.lo, 0)\n            # Augmented Bellman target\n            td_target = rewards + self.m_alpha * self.m_tau * lp_a + \\\n                        self.gamma * (1 - dones) * v_next\n        old_val = self.q_network(obs).gather(1, actions.unsqueeze(1)).squeeze(1)\n        loss = F.smooth_l1_loss(old_val, td_target)\n        self.optimizer.zero_grad()\n        loss.backward()\n        torch.nn.utils.clip_grad_norm_(self.q_network.parameters(), max_norm=10.0)\n        self.optimizer.step()\n        return {\"td_loss\": loss.item(), \"q_values\": old_val.mean().item()}"
7}
Tool ResultStep 2
OK: Replaced lines 174..242 with 67 line(s) in cleanrl/cleanrl/custom_value_discrete.py. Editable range: 174–240.

[Current file: cleanrl/cleanrl/custom_value_discrete.py | editable: 174–240 | total: 327 lines]
   171| # =====================================================================
   172| # EDITABLE: QNetwork head and ValueAlgorithm
   173| # =====================================================================
   174  class QNetwork(nn.Module):
   175      """Q-network: MLPEncoder (fixed) + head. Output: Q-values per action."""
   176  
   177      def __init__(self, obs_dim, n_actions):
   178          super().__init__()
   179          self.encoder = MLPEncoder(obs_dim)
   180          self.head = nn.Linear(ENCODER_FEATURE_DIM, n_actions)
   181  
   182      def forward(self, obs):
   183          features = self.encoder(obs)
   184          return self.head(features)
   185  
   186  
   187  class ValueAlgorithm:
   188      """Munchausen Double DQN: entropy-augmented bo
AssistantStep 3test
Tool ResultStep 3
[Test #1] (2 tests remaining; call submit(n=1) to submit this result)


## Seed 42

### cartpole-v1 (scripts/cartpole.sh)
Training metrics (last steps):
TRAIN_METRICS step=495000 td_loss=8831448.0000 q_values=26819108.0000
TRAIN_METRICS step=496000 td_loss=9037152.0000 q_values=27934608.0000
TRAIN_METRICS step=497000 td_loss=9948830.0000 q_values=29775726.0000
TRAIN_METRICS step=498000 td_loss=10187424.0000 q_values=28719050.0000
TRAIN_METRICS step=499000 td_loss=10196548.0000 q_values=29632152.0000
Evaluation (cartpole-v1):
Eval episodic_return: 9.10
Eval episodic_return: 9.10
Eval episodic_return: 9.10
Final eval return: 9.10

### lunarlander-v2 (scripts/lunarlander.sh)
Training metrics (last steps):
TRAIN_METRICS step=495000 td_loss=0.3966 q_values=13.1679
TRAIN_METRICS step=496000 td_loss=0.5025 q_values=12.6280
TRAIN_METRICS step=497000 td_loss=0.2204 q_values=14.8049
TRAIN_METRICS step=498000 td_loss=0.4568 q_values=12.3258
TRAIN_METRICS step=499000 td_loss=0.8418 q_values=10.669
AssistantStep 4edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_value_discrete.py",
4  "start_line": 174,
5  "end_line": 240,
6  "content": "class QNetwork(nn.Module):\n    \"\"\"Q-network: MLPEncoder (fixed) + head. Output: Q-values per action.\"\"\"\n\n    def __init__(self, obs_dim, n_actions):\n        super().__init__()\n        self.encoder = MLPEncoder(obs_dim)\n        self.head = nn.Linear(ENCODER_FEATURE_DIM, n_actions)\n\n    def forward(self, obs):\n        features = self.encoder(obs)\n        return self.head(features)\n\n\nclass ValueAlgorithm:\n    \"\"\"Pessimistic Munchausen Double DQN (PM-DDQN).\n    Novel combination of: (1) Double Q-learning for action selection,\n    (2) Munchausen reward augmentation adding scaled log-policy bonus for\n    implicit KL regularization, and (3) asymmetric (expectile) Huber loss\n    that penalizes Q-value overestimation more than underestimation,\n    pushing learned values toward a pessimistic expectile of the target.\n    \"\"\"\n\n    def __init__(self, obs_dim, n_actions, device, args):\n        self.device = device\n        self.n_actions = n_actions\n        self.gamma = args.gamma\n        self.total_it = 0\n        self.m_alpha = 0.9    # Munchausen scaling\n        self.m_tau = 0.03     # entropy temperature for log-policy\n        self.lo = -1.0        # log-policy clipping bound\n        self.asym_tau = 0.6   # expectile: >0.5 penalizes overestimation more\n        self.q_network = QNetwork(obs_dim, n_actions).to(device)\n        self.target_network = QNetwork(obs_dim, n_actions).to(device)\n        self.target_network.load_state_dict(self.q_network.state_dict())\n        self.optimizer = optim.Adam(self.q_network.parameters(), lr=args.learning_rate)\n\n    def select_action(self, obs, epsilon):\n        if random.random() < epsilon:\n            return random.randint(0, self.n_actions - 1)\n        obs_t = torch.tensor(obs.reshape(1, -1), device=self.device, dtype=torch.float32)\n        q_values = self.q_network(obs_t)\n        return torch.argmax(q_values, dim=1).item()\n\n    def update(self, batch, global_step):\n        self.total_it += 1\n        obs, next_obs, actions, rewards, dones = batch\n        with torch.no_grad():\n            # Double DQN: online net selects action, target net evaluates\n            next_act = self.q_network(next_obs).argmax(dim=1)\n            tgt_q = self.target_network(next_obs)\n            next_q = tgt_q[torch.arange(len(next_obs)), next_act]\n            # Munchausen reward augmentation via target net log-policy\n            q_s = self.target_network(obs)\n            lp = F.log_softmax(q_s / self.m_tau, dim=1)\n            lp_a = lp[torch.arange(len(obs)), actions].clamp(self.lo, 0)\n            aug_r = rewards + self.m_alpha * self.m_tau * lp_a\n            td_target = aug_r + self.gamma * (1 - dones) * next_q\n        old_val = self.q_network(obs).gather(1, actions.unsqueeze(1)).squeeze(1)\n        # Asymmetric Huber loss (expectile): penalizes overestimation more\n        delta = old_val - td_target\n        abs_d = torch.abs(delta)\n        huber = torch.where(abs_d <= 1.0, 0.5 * delta ** 2, abs_d - 0.5)\n        w = torch.where(delta.detach() > 0, self.asym_tau, 1.0 - self.asym_tau)\n        loss = (w * huber).mean()\n        self.optimizer.zero_grad()\n        loss.backward()\n        torch.nn.utils.clip_grad_norm_(self.q_network.parameters(), max_norm=10.0)\n        self.optimizer.step()\n        return {\"td_loss\": loss.item(), \"q_values\": old_val.mean().item()}"
7}
Tool ResultStep 4
OK: Replaced lines 174..240 with 69 line(s) in cleanrl/cleanrl/custom_value_discrete.py. Editable range: 174–242.

[Current file: cleanrl/cleanrl/custom_value_discrete.py | editable: 174–242 | total: 329 lines]
   171| # =====================================================================
   172| # EDITABLE: QNetwork head and ValueAlgorithm
   173| # =====================================================================
   174  class QNetwork(nn.Module):
   175      """Q-network: MLPEncoder (fixed) + head. Output: Q-values per action."""
   176  
   177      def __init__(self, obs_dim, n_actions):
   178          super().__init__()
   179          self.encoder = MLPEncoder(obs_dim)
   180          self.head = nn.Linear(ENCODER_FEATURE_DIM, n_actions)
   181  
   182      def forward(self, obs):
   183          features = self.encoder(obs)
   184          return self.head(features)
   185  
   186  
   187  class ValueAlgorithm:
   188      """Pessimistic Munchausen Double DQN (PM-DDQN)
AssistantStep 5test
Tool ResultStep 5
[Test #2] (1 test remaining; call submit(n=2) to submit this result)

### cartpole-v1 (scripts/cartpole.sh)
Training metrics (last steps):
TRAIN_METRICS step=495000 td_loss=176.5851 q_values=4600.3374
TRAIN_METRICS step=496000 td_loss=222.0134 q_values=4583.3789
TRAIN_METRICS step=497000 td_loss=234.0273 q_values=4714.8135
TRAIN_METRICS step=498000 td_loss=242.9607 q_values=4729.9619
TRAIN_METRICS step=499000 td_loss=122.4463 q_values=4809.4980
Evaluation (cartpole-v1):
Eval episodic_return: 21.90
Eval episodic_return: 19.50
Eval episodic_return: 23.50
Final eval return: 23.50

### lunarlander-v2 (scripts/lunarlander.sh)
Training metrics (last steps):
TRAIN_METRICS step=495000 td_loss=0.0981 q_values=-5.7713
TRAIN_METRICS step=496000 td_loss=0.2421 q_values=-9.3700
TRAIN_METRICS step=497000 td_loss=0.1250 q_values=-9.0795
TRAIN_METRICS step=498000 td_loss=0.0987 q_values=-7.6945
TRAIN_METRICS step=499000 td_loss=0.3228 q_values=-6.7049
Evaluation (lunarlander-v2):
Eval episodic_return:
AssistantStep 6edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_value_discrete.py",
4  "start_line": 174,
5  "end_line": 242,
6  "content": "class QNetwork(nn.Module):\n    \"\"\"Q-network: MLPEncoder (fixed) + head. Output: Q-values per action.\"\"\"\n\n    def __init__(self, obs_dim, n_actions):\n        super().__init__()\n        self.encoder = MLPEncoder(obs_dim)\n        self.head = nn.Linear(ENCODER_FEATURE_DIM, n_actions)\n\n    def forward(self, obs):\n        features = self.encoder(obs)\n        return self.head(features)\n\n\nclass ValueAlgorithm:\n    \"\"\"Ensembled Munchausen DQN (EM-DQN). Novel combination of:\n    (1) Munchausen reward augmentation: adds scaled log-policy bonus from\n    the target network, providing implicit KL regularization that penalizes\n    actions inconsistent with the current policy.\n    (2) Ensemble action selection: averages online and target Q-networks\n    for training data collection, yielding more robust exploration by\n    reducing the impact of any single network's overestimation.\n    (3) MSE loss for proper gradient scaling on large TD errors.\n    \"\"\"\n\n    def __init__(self, obs_dim, n_actions, device, args):\n        self.device = device\n        self.n_actions = n_actions\n        self.gamma = args.gamma\n        self.total_it = 0\n        self.m_alpha = 0.9    # Munchausen scaling factor\n        self.m_tau = 0.03     # entropy temperature for log-policy\n        self.lo = -1.0        # log-policy clipping lower bound\n        self.q_network = QNetwork(obs_dim, n_actions).to(device)\n        self.target_network = QNetwork(obs_dim, n_actions).to(device)\n        self.target_network.load_state_dict(self.q_network.state_dict())\n        self.optimizer = optim.Adam(self.q_network.parameters(), lr=args.learning_rate)\n\n    def select_action(self, obs, epsilon):\n        \"\"\"Ensemble epsilon-greedy: average online+target Q for selection.\"\"\"\n        if random.random() < epsilon:\n            return random.randint(0, self.n_actions - 1)\n        obs_t = torch.tensor(obs.reshape(1, -1), device=self.device, dtype=torch.float32)\n        with torch.no_grad():\n            q_on = self.q_network(obs_t)\n            q_tg = self.target_network(obs_t)\n            q_ens = 0.5 * q_on + 0.5 * q_tg\n        return torch.argmax(q_ens, dim=1).item()\n\n    def update(self, batch, global_step):\n        self.total_it += 1\n        obs, next_obs, actions, rewards, dones = batch\n        with torch.no_grad():\n            # Standard max target from target network (proven stable)\n            target_max = self.target_network(next_obs).max(dim=1)[0]\n            # Munchausen reward augmentation via target net's log-policy\n            q_s = self.target_network(obs)\n            lp = F.log_softmax(q_s / self.m_tau, dim=1)\n            lp_a = lp[torch.arange(len(obs)), actions].clamp(self.lo, 0)\n            aug_r = rewards + self.m_alpha * self.m_tau * lp_a\n            td_target = aug_r + self.gamma * (1 - dones) * target_max\n        old_val = self.q_network(obs).gather(1, actions.unsqueeze(1)).squeeze(1)\n        loss = F.mse_loss(old_val, td_target)\n        self.optimizer.zero_grad()\n        loss.backward()\n        torch.nn.utils.clip_grad_norm_(self.q_network.parameters(), max_norm=10.0)\n        self.optimizer.step()\n        return {\"td_loss\": loss.item(), \"q_values\": old_val.mean().item()}"
7}
Tool ResultStep 6
OK: Replaced lines 174..242 with 67 line(s) in cleanrl/cleanrl/custom_value_discrete.py. Editable range: 174–240.

[Current file: cleanrl/cleanrl/custom_value_discrete.py | editable: 174–240 | total: 327 lines]
   171| # =====================================================================
   172| # EDITABLE: QNetwork head and ValueAlgorithm
   173| # =====================================================================
   174  class QNetwork(nn.Module):
   175      """Q-network: MLPEncoder (fixed) + head. Output: Q-values per action."""
   176  
   177      def __init__(self, obs_dim, n_actions):
   178          super().__init__()
   179          self.encoder = MLPEncoder(obs_dim)
   180          self.head = nn.Linear(ENCODER_FEATURE_DIM, n_actions)
   181  
   182      def forward(self, obs):
   183          features = self.encoder(obs)
   184          return self.head(features)
   185  
   186  
   187  class ValueAlgorithm:
   188      """Ensembled Munchausen DQN (EM-DQN). Novel co
AssistantStep 7test
Tool ResultStep 7
[Test #3] (0 tests remaining)


## Seed 42

### cartpole-v1 (scripts/cartpole.sh)
Training metrics (last steps):
TRAIN_METRICS step=495000 td_loss=0.0164 q_values=101.7867
TRAIN_METRICS step=496000 td_loss=0.0138 q_values=101.6135
TRAIN_METRICS step=497000 td_loss=0.0096 q_values=101.6237
TRAIN_METRICS step=498000 td_loss=0.0074 q_values=101.6280
TRAIN_METRICS step=499000 td_loss=0.0139 q_values=101.9030
Evaluation (cartpole-v1):
Eval episodic_return: 500.00
Eval episodic_return: 500.00
Eval episodic_return: 500.00
Final eval return: 500.00

### lunarlander-v2 (scripts/lunarlander.sh)
Training metrics (last steps):
TRAIN_METRICS step=495000 td_loss=0.6554 q_values=27.0310
TRAIN_METRICS step=496000 td_loss=1.4189 q_values=26.3545
TRAIN_METRICS step=497000 td_loss=1.8950 q_values=31.8224
TRAIN_METRICS step=498000 td_loss=2.4778 q_values=24.1690
TRAIN_METRICS step=499000 td_loss=1.1699 q_values=29.6376
Evaluation (lunarlander-v2):
Eval episodic_return: 186.41
Eval episodic_return: 186.76