Agent Conversation: anthropic/claude-opus-4.6

Model: anthropic/claude-opus-4.6
Total steps: 6
Messages: 13
UserStep 0

Task: rl-onpolicy-continuous

Online RL: On-Policy Actor-Critic for Continuous Control

Objective

Design and implement an on-policy actor-critic RL algorithm for continuous control. Your code goes in custom_onpolicy_continuous.py. Three reference implementations (PPO, RPO, PPO-Penalty) are provided as read-only.

Background

On-policy methods collect trajectories using the current policy, compute advantages via Generalized Advantage Estimation (GAE), and update the policy using mini-batch optimization. Key challenges include sample efficiency, stability of policy updates, and balancing exploration with exploitation. Different approaches address these through clipped surrogate objectives, stochasticity injection, or direct policy gradient estimation.

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 HalfCheetah-v4, Hopper-v4, Walker2d-v4. 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_onpolicy_continuous.py [EDITABLE — lines 175–221 only]

     1: # Custom on-policy continuous RL algorithm for MLS-Bench
     2: #
     3: # FIXED sections: config, env, utilities, network architecture, training loop.
     4: # EDITABLE section: get_action_and_value method and compute_losses function.
     5: import copy
     6: import os
     7: import random
     8: import time
     9: from dataclasses import dataclass
    10: 
    11: import gymnasium as gym
    12: import numpy as np
    13: import torch
    14: import torch.nn as nn
    15: import torch.nn.functional as F
    16: import torch.optim as optim
    17: import tyro
    18: from torch.distributions.normal import Normal
    19: 
    20: 
    21: # =====================================================================
    22: # FIXED: Configuration
    23: # =====================================================================
    24: @dataclass
    25: class Args:
    26:     exp_name: str = os.path.basename(__file__)[: -len(".py")]
    27:     """the name of this experiment"""
    28:     seed: int = 1
    29:     """seed of the experiment"""
    30:     torch_deterministic: bool = True
    31:     """if toggled, `torch.backends.cudnn.deterministic=False`"""
    32:     cuda: bool = True
    33:     """if toggled, cuda will be enabled by default"""
    34: 
    35:     # Algorithm specific arguments
    36:     env_id: str = "HalfCheetah-v4"
    37:     """the id of the environment"""
    38:     total_timesteps: int = 1000000
    39:     """total timesteps of the experiments"""
    40:     learning_rate: float = 3e-4
    41:     """the l
AssistantStep 1edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_onpolicy_continuous.py",
4  "start_line": 175,
5  "end_line": 221,
6  "content": "    def get_action_and_value(self, obs, action=None):\n        action_mean = self.actor_mean(obs)\n        action_logstd = self.actor_logstd.expand_as(action_mean)\n        action_std = torch.exp(action_logstd)\n\n        # Random Perturbation Optimization (RPO): inject uniform noise into\n        # the action mean before constructing the Gaussian. Each forward pass\n        # sees a different perturbation, which randomizes the importance-\n        # sampling ratio and implicitly enlarges the exploration region.\n        _rpo_alpha = 0.5\n        z = torch.FloatTensor(action_mean.shape).uniform_(\n            -_rpo_alpha, _rpo_alpha\n        ).to(action_mean.device)\n        action_mean = action_mean + z\n\n        probs = Normal(action_mean, action_std)\n        if action is None:\n            action = probs.sample()\n        return action, probs.log_prob(action).sum(1), probs.entropy().sum(1), self.critic(obs)\n\n\ndef compute_losses(agent, mb_obs, mb_actions, mb_logprobs, mb_advantages, mb_returns, mb_values, args):\n    \"\"\"Stochastic Trust-Region PPO (STP-PPO).\n\n    Combines RPO exploration (via perturbed action means) with:\n    1. PPO clipped surrogate objective\n    2. Clipped value-function loss\n    3. Advantage-calibrated entropy: entropy bonus is modulated per sample\n       so that states with negative advantages (under-performing) receive a\n       larger entropy push (explore more) while states with positive\n       advantages (well-performing) get a smaller push (exploit more).\n    \"\"\"\n    # Hardcoded hyperparameters for our novel components\n    _ent_coef = 0.005        # base entropy coefficient (overrides default 0.0)\n    _adv_ent_modulation = 0.4  # how much advantages modulate entropy weight\n\n    _, newlogprob, entropy, newvalue = agent.get_action_and_value(mb_obs, mb_actions)\n    logratio = newlogprob - mb_logprobs\n    ratio = logratio.exp()\n\n    with torch.no_grad():\n        approx_kl = ((ratio - 1) - logratio).mean()\n        clipfrac = ((ratio - 1.0).abs() > args.clip_coef).float().mean().item()\n\n    # ---- Policy loss: PPO clipped surrogate ----\n    pg_loss1 = -mb_advantages * ratio\n    pg_loss2 = -mb_advantages * torch.clamp(ratio, 1 - args.clip_coef, 1 + args.clip_coef)\n    pg_loss = torch.max(pg_loss1, pg_loss2).mean()\n\n    # ---- Value loss: clipped ----\n    newvalue = newvalue.view(-1)\n    if args.clip_vloss:\n        v_loss_unclipped = (newvalue - mb_returns) ** 2\n        v_clipped = mb_values + torch.clamp(\n            newvalue - mb_values, -args.clip_coef, args.clip_coef\n        )\n        v_loss_clipped = (v_clipped - mb_returns) ** 2\n        v_loss = 0.5 * torch.max(v_loss_unclipped, v_loss_clipped).mean()\n    else:\n        v_loss = 0.5 * ((newvalue - mb_returns) ** 2).mean()\n\n    # ---- Advantage-Calibrated Entropy (ACE) ----\n    # States with negative normalised advantages -> weight > 1 (explore more)\n    # States with positive normalised advantages -> weight < 1 (exploit more)\n    with torch.no_grad():\n        ace_weight = 1.0 - _adv_ent_modulation * torch.tanh(mb_advantages)\n    entropy_loss = (entropy * ace_weight).mean()\n\n    loss = pg_loss - _ent_coef * entropy_loss + v_loss * args.vf_coef\n\n    return loss, pg_loss, v_loss, entropy_loss, approx_kl, clipfrac\n\n\n"
7}
Tool ResultStep 1
OK: Replaced lines 175..221 with 73 line(s) in cleanrl/cleanrl/custom_onpolicy_continuous.py. Editable range: 175–247.

[Current file: cleanrl/cleanrl/custom_onpolicy_continuous.py | editable: 175–247 | total: 412 lines]
   172|     # =================================================================
   173|     # EDITABLE: get_action_and_value and compute_losses
   174|     # =================================================================
   175      def get_action_and_value(self, obs, action=None):
   176          action_mean = self.actor_mean(obs)
   177          action_logstd = self.actor_logstd.expand_as(action_mean)
   178          action_std = torch.exp(action_logstd)
   179  
   180          # Random Perturbation Optimization (RPO): inject uniform noise into
   181          # the action mean before constructing the Gaussian. Each forward pass
   182          # sees a different perturbation, which randomizes the importance-
   183          # sampling ratio and implicitly enlarg
AssistantStep 2test
Tool ResultStep 2
[Test #1] (2 tests remaining; call test(submit=1) to submit this result)


## Seed 42

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=0.0032 vf_loss=0.0544 entropy=16.8484 approx_kl=0.0190 clipfrac=0.3201
TRAIN_METRICS step=993280 pg_loss=0.0025 vf_loss=0.0088 entropy=17.3134 approx_kl=0.0200 clipfrac=0.3445
TRAIN_METRICS step=995328 pg_loss=0.0406 vf_loss=0.0066 entropy=17.4849 approx_kl=0.0278 clipfrac=0.3287
TRAIN_METRICS step=997376 pg_loss=-0.0369 vf_loss=0.0069 entropy=17.4268 approx_kl=0.0306 clipfrac=0.3330
TRAIN_METRICS step=999424 pg_loss=0.0156 vf_loss=0.0084 entropy=17.5236 approx_kl=0.0309 clipfrac=0.3234
Evaluation (halfcheetah-v4):
Eval episodic_return: 871.24
Eval episodic_return: 897.59
Eval episodic_return: 885.73
Final eval return: 885.73

### swimmer-v4 (scripts/swimmer.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0018 vf_loss=0.0093 entropy=5.3909 approx_kl=0.0059 clipfrac=0.12
AssistantStep 3edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_onpolicy_continuous.py",
4  "start_line": 175,
5  "end_line": 247,
6  "content": "    def get_action_and_value(self, obs, action=None):\n        action_mean = self.actor_mean(obs)\n        action_logstd = self.actor_logstd.expand_as(action_mean)\n        action_std = torch.exp(action_logstd)\n\n        # Scale-Adaptive Random Perturbation (SARP):\n        # Unlike fixed-scale RPO, perturbation scales with the current policy\n        # std so it shrinks as the policy becomes more certain, preventing\n        # over-perturbation in precise-control tasks while preserving\n        # exploration benefits during early training.\n        _sarp_alpha = 0.15\n        z = torch.FloatTensor(action_mean.shape).uniform_(-1.0, 1.0).to(action_mean.device)\n        action_mean = action_mean + _sarp_alpha * action_std.detach() * z\n\n        probs = Normal(action_mean, action_std)\n        if action is None:\n            action = probs.sample()\n        return action, probs.log_prob(action).sum(1), probs.entropy().sum(1), self.critic(obs)\n\n\ndef compute_losses(agent, mb_obs, mb_actions, mb_logprobs, mb_advantages, mb_returns, mb_values, args):\n    \"\"\"Advantage-Weighted PPO with Scale-Adaptive Perturbation (AW-SARP-PPO).\n\n    Novel combination:\n    1. SARP exploration in get_action_and_value (std-proportional perturbation)\n    2. Exponential advantage weighting: samples with higher advantages get\n       larger gradient weight, focusing policy updates on clearly beneficial\n       actions — bridging PPO and AWR philosophies.\n    3. PPO clipped surrogate ensures trust region stability.\n    4. Clipped value function loss.\n    \"\"\"\n    _awr_beta = 2.0         # advantage weighting temperature\n    _awr_max_weight = 10.0   # stability clamp\n\n    _, newlogprob, entropy, newvalue = agent.get_action_and_value(mb_obs, mb_actions)\n    logratio = newlogprob - mb_logprobs\n    ratio = logratio.exp()\n\n    with torch.no_grad():\n        approx_kl = ((ratio - 1) - logratio).mean()\n        clipfrac = ((ratio - 1.0).abs() > args.clip_coef).float().mean().item()\n\n    # ---- Advantage-based importance weights (AWR-style) ----\n    # Exponential weighting focuses gradient on high-advantage samples.\n    # Since weights > 0, the max(pg1, pg2) factorises cleanly:\n    #   max(w*f, w*g) = w * max(f, g)  =>  correct PPO clipping behaviour preserved.\n    with torch.no_grad():\n        weights = torch.exp(mb_advantages / _awr_beta)\n        weights = torch.clamp(weights, max=_awr_max_weight)\n        weights = weights / (weights.mean() + 1e-8)   # normalise to mean 1\n\n    # ---- Policy loss: weighted PPO clipped surrogate ----\n    pg_loss1 = -mb_advantages * ratio * weights\n    pg_loss2 = -mb_advantages * torch.clamp(ratio, 1 - args.clip_coef, 1 + args.clip_coef) * weights\n    pg_loss = torch.max(pg_loss1, pg_loss2).mean()\n\n    # ---- Value loss: clipped ----\n    newvalue = newvalue.view(-1)\n    if args.clip_vloss:\n        v_loss_unclipped = (newvalue - mb_returns) ** 2\n        v_clipped = mb_values + torch.clamp(\n            newvalue - mb_values, -args.clip_coef, args.clip_coef\n        )\n        v_loss_clipped = (v_clipped - mb_returns) ** 2\n        v_loss = 0.5 * torch.max(v_loss_unclipped, v_loss_clipped).mean()\n    else:\n        v_loss = 0.5 * ((newvalue - mb_returns) ** 2).mean()\n\n    entropy_loss = entropy.mean()\n    loss = pg_loss - args.ent_coef * entropy_loss + v_loss * args.vf_coef\n\n    return loss, pg_loss, v_loss, entropy_loss, approx_kl, clipfrac\n\n\n"
7}
Tool ResultStep 3
OK: Replaced lines 175..247 with 74 line(s) in cleanrl/cleanrl/custom_onpolicy_continuous.py. Editable range: 175–248.

[Current file: cleanrl/cleanrl/custom_onpolicy_continuous.py | editable: 175–248 | total: 413 lines]
   172|     # =================================================================
   173|     # EDITABLE: get_action_and_value and compute_losses
   174|     # =================================================================
   175      def get_action_and_value(self, obs, action=None):
   176          action_mean = self.actor_mean(obs)
   177          action_logstd = self.actor_logstd.expand_as(action_mean)
   178          action_std = torch.exp(action_logstd)
   179  
   180          # Scale-Adaptive Random Perturbation (SARP):
   181          # Unlike fixed-scale RPO, perturbation scales with the current policy
   182          # std so it shrinks as the policy becomes more certain, preventing
   183          # over-perturbation in precise-control tasks while preservin
AssistantStep 4test
Tool ResultStep 4
[Test #2] (1 test remaining; call test(submit=2) to submit this result)

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.1989 vf_loss=0.0720 entropy=-6.3696 approx_kl=0.0489 clipfrac=0.4721
TRAIN_METRICS step=993280 pg_loss=-0.2516 vf_loss=0.0111 entropy=-6.3698 approx_kl=0.0409 clipfrac=0.4806
TRAIN_METRICS step=995328 pg_loss=-0.2549 vf_loss=0.0057 entropy=-6.3701 approx_kl=0.0581 clipfrac=0.4722
TRAIN_METRICS step=997376 pg_loss=-0.2049 vf_loss=0.0043 entropy=-6.3706 approx_kl=0.0555 clipfrac=0.4667
TRAIN_METRICS step=999424 pg_loss=-0.1728 vf_loss=0.0061 entropy=-6.3708 approx_kl=0.0543 clipfrac=0.4606
Evaluation (halfcheetah-v4):
Eval episodic_return: 1699.68
Eval episodic_return: 1712.04
Eval episodic_return: 1708.78
Final eval return: 1708.78

### swimmer-v4 (scripts/swimmer.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.5514 vf_loss=0.0000 entropy=-7.2521 approx_kl=0.0168 clipfrac=0.2220
TR
AssistantStep 5edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_onpolicy_continuous.py",
4  "start_line": 175,
5  "end_line": 248,
6  "content": "    def get_action_and_value(self, obs, action=None):\n        action_mean = self.actor_mean(obs)\n        action_logstd = self.actor_logstd.expand_as(action_mean)\n        action_std = torch.exp(action_logstd)\n        probs = Normal(action_mean, action_std)\n        if action is None:\n            action = probs.sample()\n        return action, probs.log_prob(action).sum(1), probs.entropy().sum(1), self.critic(obs)\n\n\ndef compute_losses(agent, mb_obs, mb_actions, mb_logprobs, mb_advantages, mb_returns, mb_values, args):\n    \"\"\"Asymmetric-Clip PPO with Unconstrained Value Learning (ACU-PPO).\n\n    Novel contributions over standard PPO:\n    1. Asymmetric policy clipping: positive advantages use a wider upper clip\n       (1 + 2*epsilon) allowing more aggressive exploitation of discovered\n       good actions, while negative advantages retain standard symmetric clip\n       for conservative avoidance of harmful actions.  This addresses PPO's\n       over-conservative treatment of high-advantage transitions without\n       sacrificing trust-region stability for negative-advantage corrections.\n    2. Unconstrained value loss: removes the value-function clipping used in\n       standard PPO. Value clipping can impede value accuracy by preventing\n       necessary corrections; removing it allows faster convergence to\n       accurate value estimates that improve advantage signal quality.\n    \"\"\"\n    _pos_clip_mult = 2.0   # upper clip multiplier for positive advantages\n\n    _, newlogprob, entropy, newvalue = agent.get_action_and_value(mb_obs, mb_actions)\n    logratio = newlogprob - mb_logprobs\n    ratio = logratio.exp()\n\n    with torch.no_grad():\n        approx_kl = ((ratio - 1) - logratio).mean()\n        clipfrac = ((ratio - 1.0).abs() > args.clip_coef).float().mean().item()\n\n    # ---- Asymmetric clipping ----\n    clip_lo = 1.0 - args.clip_coef\n    clip_hi_pos = 1.0 + args.clip_coef * _pos_clip_mult   # wider for A >= 0\n    clip_hi_neg = 1.0 + args.clip_coef                    # standard for A < 0\n\n    ratio_clip_pos = torch.clamp(ratio, clip_lo, clip_hi_pos)\n    ratio_clip_neg = torch.clamp(ratio, clip_lo, clip_hi_neg)\n    ratio_clipped = torch.where(mb_advantages >= 0, ratio_clip_pos, ratio_clip_neg)\n\n    pg_loss1 = -mb_advantages * ratio\n    pg_loss2 = -mb_advantages * ratio_clipped\n    pg_loss = torch.max(pg_loss1, pg_loss2).mean()\n\n    # ---- Unconstrained value loss (plain MSE) ----\n    newvalue = newvalue.view(-1)\n    v_loss = 0.5 * ((newvalue - mb_returns) ** 2).mean()\n\n    entropy_loss = entropy.mean()\n    loss = pg_loss - args.ent_coef * entropy_loss + v_loss * args.vf_coef\n\n    return loss, pg_loss, v_loss, entropy_loss, approx_kl, clipfrac\n\n\n"
7}
Tool ResultStep 5
OK: Replaced lines 175..248 with 58 line(s) in cleanrl/cleanrl/custom_onpolicy_continuous.py. Editable range: 175–232.

[Current file: cleanrl/cleanrl/custom_onpolicy_continuous.py | editable: 175–232 | total: 397 lines]
   172|     # =================================================================
   173|     # EDITABLE: get_action_and_value and compute_losses
   174|     # =================================================================
   175      def get_action_and_value(self, obs, action=None):
   176          action_mean = self.actor_mean(obs)
   177          action_logstd = self.actor_logstd.expand_as(action_mean)
   178          action_std = torch.exp(action_logstd)
   179          probs = Normal(action_mean, action_std)
   180          if action is None:
   181              action = probs.sample()
   182          return action, probs.log_prob(action).sum(1), probs.entropy().sum(1), self.critic(obs)
   183  
   184  
   185  def compute_losses(agent, mb_obs, mb_actions, mb_lo
AssistantStep 6test
Tool ResultStep 6
[Test #3] (0 tests remaining; auto-submitted as final)


## Seed 42

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0053 vf_loss=0.1047 entropy=6.3897 approx_kl=0.0009 clipfrac=0.0000
TRAIN_METRICS step=993280 pg_loss=-0.0065 vf_loss=0.0136 entropy=6.3902 approx_kl=0.0006 clipfrac=0.0000
TRAIN_METRICS step=995328 pg_loss=-0.0060 vf_loss=0.0083 entropy=6.3904 approx_kl=0.0005 clipfrac=0.0000
TRAIN_METRICS step=997376 pg_loss=0.0032 vf_loss=0.0075 entropy=6.3901 approx_kl=0.0003 clipfrac=0.0000
TRAIN_METRICS step=999424 pg_loss=-0.0015 vf_loss=0.0132 entropy=6.3903 approx_kl=0.0001 clipfrac=0.0000
Evaluation (halfcheetah-v4):
Eval episodic_return: 1203.89
Eval episodic_return: 1186.70
Eval episodic_return: 1232.93
Final eval return: 1232.93

### swimmer-v4 (scripts/swimmer.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0024 vf_loss=0.0185 entropy=5.1436 approx_kl=0.0004 clipfrac=0.0000
TRAIN_METRICS