Agent Conversation: gpt-5.4-pro

Model: gpt-5.4-pro
Total steps: 20
Messages: 69
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.

Evaluation

Trained and evaluated on three MuJoCo locomotion environments: HalfCheetah-v4, Hopper-v4, Walker2d-v4. Metric: mean episodic return over 10 evaluation episodes (higher is better).

cleanrl/cleanrl/custom_onpolicy_continuous.py [EDITABLE — lines 142–217 only]

     1: # Custom on-policy continuous RL algorithm for MLS-Bench
     2: #
     3: # EDITABLE section: Agent and compute_losses.
     4: # FIXED sections: everything else (config, env, utilities, training loop).
     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 learning rate of the optimizer"""
    42:     num_envs: int = 1
    43:     """the number of parallel game environments"""
    44:     num_steps: int = 2048
    45:     """the number of steps to run in each environment per policy rollout"""
    46:     anneal_lr: bool = True
    47:     """Toggle learning rate annealing for policy and value networks"""
    48:     gamma: float = 0.99
    49:     """
AssistantStep 1edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_onpolicy_continuous.py",
4  "content": "class Agent(nn.Module):\n    \"\"\"Squashed-Gaussian PPO agent with orthogonal init and state-dependent std.\"\"\"\n\n    def __init__(self, obs_dim, action_dim):\n        super().__init__()\n        h = 256\n        self.critic = nn.Sequential(\n            layer_init(nn.Linear(obs_dim, h)), nn.Tanh(),\n            layer_init(nn.Linear(h, h)), nn.Tanh(),\n            layer_init(nn.Linear(h, 1), std=1.0),\n        )\n        self.actor = nn.Sequential(\n            layer_init(nn.Linear(obs_dim, h)), nn.Tanh(),\n            layer_init(nn.Linear(h, h)), nn.Tanh(),\n        )\n        self.actor_mean = layer_init(nn.Linear(h, action_dim), std=0.01)\n        self.actor_logstd = layer_init(nn.Linear(h, action_dim), std=0.01, bias_const=-0.5)\n\n    def get_value(self, obs):\n        return self.critic(obs)\n\n    def get_action_and_value(self, obs, action=None):\n        hidden = self.actor(obs)\n        mean = self.actor_mean(hidden)\n        logstd = self.actor_logstd(hidden).clamp(-5.0, 1.0)\n        std = logstd.exp()\n        probs = Normal(mean, std)\n        if action is None:\n            raw_action = probs.rsample()\n            action = torch.tanh(raw_action)\n        else:\n            action = action.clamp(-0.999999, 0.999999)\n            raw_action = 0.5 * (torch.log1p(action) - torch.log1p(-action))\n        squash_correction = 2.0 * (np.log(2.0) - raw_action - F.softplus(-2.0 * raw_action))\n        log_prob = probs.log_prob(raw_action) - squash_correction\n        return action, log_prob.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    \"\"\"PPO clipped surrogate objective + clipped value loss for squashed Gaussian policy.\"\"\"\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    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    newvalue = newvalue.view(-1)\n    if args.clip_vloss:\n        v_loss_unclipped = (newvalue - mb_returns) ** 2\n        v_clipped = mb_values + torch.clamp(newvalue - mb_values, -args.clip_coef, args.clip_coef)\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 + args.vf_coef * v_loss\n    return loss, pg_loss, v_loss, entropy_loss, approx_kl, clipfrac\n",
5  "after_line": 142,
6  "start_line": 142,
7  "end_line": 215
8}
Tool ResultStep 1
OK: Replaced lines 142..215 with 64 line(s) in cleanrl/cleanrl/custom_onpolicy_continuous.py. Editable range: 142–207.

[Current file: cleanrl/cleanrl/custom_onpolicy_continuous.py | editable: 142–207 | total: 361 lines]
   139| # =====================================================================
   140| # EDITABLE: Agent and compute_losses
   141| # =====================================================================
   142  class Agent(nn.Module):
   143      """Squashed-Gaussian PPO agent with orthogonal init and state-dependent std."""
   144  
   145      def __init__(self, obs_dim, action_dim):
   146          super().__init__()
   147          h = 256
   148          self.critic = nn.Sequential(
   149              layer_init(nn.Linear(obs_dim, h)), nn.Tanh(),
   150              layer_init(nn.Linear(h, h)), nn.Tanh(),
   151              layer_init(nn.Linear(h, 1), std=1.0),
   152          )
   153          self.actor = nn.Sequential(
   154              layer_init(nn.Line
AssistantStep 2test
Tool Input
1{
2  "is_final": false,
3  "use_last": false
4}
Tool ResultStep 2
## Seed 42

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0292 vf_loss=0.0833 entropy=-4.3839 approx_kl=0.0088 clipfrac=0.0803
TRAIN_METRICS step=993280 pg_loss=-0.0158 vf_loss=0.0090 entropy=-5.1564 approx_kl=0.0108 clipfrac=0.0810
TRAIN_METRICS step=995328 pg_loss=0.0319 vf_loss=0.0040 entropy=-5.1889 approx_kl=0.0073 clipfrac=0.0482
TRAIN_METRICS step=997376 pg_loss=-0.0319 vf_loss=0.0164 entropy=0.2728 approx_kl=0.0035 clipfrac=0.0214
TRAIN_METRICS step=999424 pg_loss=-0.0033 vf_loss=0.0013 entropy=-0.2246 approx_kl=0.0026 clipfrac=0.0118
Evaluation (halfcheetah-v4):
Eval episodic_return: 5038.33
Eval episodic_return: 4089.42
Eval episodic_return: 4531.68
Final eval return: 4531.68

### hopper-v4 (scripts/hopper.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0094 vf_loss=0.0092 entropy=2.9639 approx_kl=0.0094 clipfrac=0.0484
TRAIN_METRICS step=993280 pg_loss=-0.0027 vf_loss=0.0364 entropy=2.
AssistantStep 3test
Tool Input
1{
2  "is_final": true,
3  "use_last": true
4}
Tool ResultStep 3
## Seed 42

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0292 vf_loss=0.0833 entropy=-4.3839 approx_kl=0.0088 clipfrac=0.0803
TRAIN_METRICS step=993280 pg_loss=-0.0158 vf_loss=0.0090 entropy=-5.1564 approx_kl=0.0108 clipfrac=0.0810
TRAIN_METRICS step=995328 pg_loss=0.0319 vf_loss=0.0040 entropy=-5.1889 approx_kl=0.0073 clipfrac=0.0482
TRAIN_METRICS step=997376 pg_loss=-0.0319 vf_loss=0.0164 entropy=0.2728 approx_kl=0.0035 clipfrac=0.0214
TRAIN_METRICS step=999424 pg_loss=-0.0033 vf_loss=0.0013 entropy=-0.2246 approx_kl=0.0026 clipfrac=0.0118
Evaluation (halfcheetah-v4):
Eval episodic_return: 5038.33
Eval episodic_return: 4089.42
Eval episodic_return: 4531.68
Final eval return: 4531.68

### hopper-v4 (scripts/hopper.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0094 vf_loss=0.0092 entropy=2.9639 approx_kl=0.0094 clipfrac=0.0484
TRAIN_METRICS step=993280 pg_loss=-0.0027 vf_loss=0.0364 entropy=2.
AssistantStep 1edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_onpolicy_continuous.py",
4  "content": "    def get_action_and_value(self, obs, action=None):\n        if not hasattr(self, \"_init_done\"):\n            self._init_done = True\n            layer_init(self.critic[0])\n            layer_init(self.critic[2])\n            layer_init(self.critic[4], std=1.0)\n            layer_init(self.actor_mean[0])\n            layer_init(self.actor_mean[2])\n            layer_init(self.actor_mean[4], std=0.01)\n            nn.init.constant_(self.actor_logstd, -0.5)\n\n        action_mean = torch.clamp(self.actor_mean(obs), -5.0, 5.0)\n        action_logstd = torch.clamp(self.actor_logstd, -4.0, 1.0).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    \"\"\"Engineered PPO loss with clipped policy/value updates and stabilizers.\"\"\"\n    if args.target_kl is None:\n        args.target_kl = 0.03\n    args.clip_vloss = True\n\n    clip_coef = args.clip_coef\n    _, newlogprob, entropy, newvalue = agent.get_action_and_value(mb_obs, mb_actions)\n    logratio = torch.clamp(newlogprob - mb_logprobs, -20.0, 20.0)\n    ratio = logratio.exp()\n\n    with torch.no_grad():\n        approx_kl = ((ratio - 1) - logratio).mean()\n        clipfrac = ((ratio - 1.0).abs() > clip_coef).float().mean().item()\n\n    mb_advantages = torch.clamp(mb_advantages, -5.0, 5.0)\n    pg_loss1 = -mb_advantages * ratio\n    pg_loss2 = -mb_advantages * torch.clamp(ratio, 1 - clip_coef, 1 + clip_coef)\n    pg_loss = torch.max(pg_loss1, pg_loss2).mean()\n\n    newvalue = newvalue.view(-1)\n    v_loss_unclipped = (newvalue - mb_returns) ** 2\n    v_clipped = mb_values + torch.clamp(newvalue - mb_values, -clip_coef, clip_coef)\n    v_loss_clipped = (v_clipped - mb_returns) ** 2\n    v_loss = 0.5 * torch.max(v_loss_unclipped, v_loss_clipped).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",
5  "after_line": 0,
6  "start_line": 175,
7  "end_line": 219
8}
Tool ResultStep 1
OK: Replaced lines 175..219 with 50 line(s) in cleanrl/cleanrl/custom_onpolicy_continuous.py. Editable range: 175–226.

[Current file: cleanrl/cleanrl/custom_onpolicy_continuous.py | editable: 175–226 | total: 391 lines]
   172|     # =================================================================
   173|     # EDITABLE: get_action_and_value and compute_losses
   174|     # =================================================================
   175      def get_action_and_value(self, obs, action=None):
   176          if not hasattr(self, "_init_done"):
   177              self._init_done = True
   178              layer_init(self.critic[0])
   179              layer_init(self.critic[2])
   180              layer_init(self.critic[4], std=1.0)
   181              layer_init(self.actor_mean[0])
   182              layer_init(self.actor_mean[2])
   183              layer_init(self.actor_mean[4], std=0.01)
   184              nn.init.constant_(self.actor_logstd, -0.5)
   185  
   186       
AssistantStep 1edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_onpolicy_continuous.py",
4  "content": "    def get_action_and_value(self, obs, action=None):\n        \"\"\"Bounded Gaussian policy with boundary-aware exploration.\n\n        We sample in an unconstrained space and squash with tanh so that the\n        policy matches the Box action bounds more faithfully than an\n        unsquashed Gaussian followed by environment-side clipping.\n        Additionally, the exploration scale is reduced near saturated means,\n        which improves stability for precise-control regimes.\n        \"\"\"\n        eps = 1e-6\n        action_mean = self.actor_mean(obs)\n\n        # Mean-dependent exploration: keep broad exploration near the origin\n        # but shrink it smoothly as the policy pushes toward action bounds.\n        squash_mean = torch.tanh(action_mean)\n        mean_gate = 1.0 - squash_mean.pow(2)\n        action_logstd = self.actor_logstd.expand_as(action_mean) + 0.5 * torch.log(mean_gate + eps)\n        action_logstd = torch.clamp(action_logstd, -5.0, 2.0)\n        action_std = torch.exp(action_logstd)\n        probs = Normal(action_mean, action_std)\n\n        if action is None:\n            pre_tanh_action = probs.rsample()\n            action = torch.tanh(pre_tanh_action)\n        else:\n            action = torch.clamp(action, -1.0 + eps, 1.0 - eps)\n            pre_tanh_action = 0.5 * (torch.log1p(action) - torch.log1p(-action))\n\n        logprob = probs.log_prob(pre_tanh_action) - torch.log(1.0 - action.pow(2) + eps)\n        logprob = logprob.sum(1)\n\n        # Monte-Carlo entropy estimate for the squashed policy.\n        entropy = probs.entropy().sum(1) + torch.log(1.0 - action.pow(2) + eps).sum(1)\n        return action, logprob, entropy, self.critic(obs)\n\n\ndef compute_losses(agent, mb_obs, mb_actions, mb_logprobs, mb_advantages, mb_returns, mb_values, args):\n    \"\"\"Hybrid bounded PPO with positive-advantage regression and expectile critic.\n\n    Main ingredients:\n      1) tanh-squashed bounded policy (implemented in get_action_and_value)\n      2) asymmetric PPO clipping: more room to reinforce good actions and a\n         tighter correction on bad ones\n      3) positive-advantage log-ratio bonus: an on-policy AWR-style term that\n         selectively boosts high-advantage samples without abandoning PPO's\n         trust-region behavior\n      4) clipped expectile value regression for a slightly optimistic critic\n    \"\"\"\n    _awr_coef = 0.5\n    _awr_beta = 0.75\n    _kl_coef = 0.02\n    _expectile = 0.65\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 - 1.0) - logratio).mean()\n        clipfrac = ((ratio - 1.0).abs() > args.clip_coef).float().mean().item()\n\n    adv = torch.clamp(mb_advantages, -4.0, 4.0)\n    shaped_adv = torch.where(\n        adv >= 0,\n        adv * (1.0 + 0.25 * adv),\n        0.75 * adv,\n    )\n\n    pos_clip_ratio = torch.clamp(ratio, 1.0 - args.clip_coef, 1.0 + 1.5 * args.clip_coef)\n    neg_clip_ratio = torch.clamp(ratio, 1.0 - 0.75 * args.clip_coef, 1.0 + args.clip_coef)\n    clipped_ratio = torch.where(shaped_adv >= 0, pos_clip_ratio, neg_clip_ratio)\n    ppo_loss = -torch.min(ratio * shaped_adv, clipped_ratio * shaped_adv).mean()\n\n    with torch.no_grad():\n        pos_weights = torch.exp(torch.clamp(torch.relu(adv) / _awr_beta, max=2.0)) - 1.0\n        pos_weights = pos_weights / (pos_weights.mean() + 1e-8)\n    awr_loss = -(logratio * pos_weights).mean()\n\n    kl_loss = ((ratio - 1.0) - logratio).mean()\n    pg_loss = ppo_loss + _awr_coef * awr_loss + _kl_coef * kl_loss\n\n    newvalue = newvalue.view(-1)\n    v_error = mb_returns - newvalue\n    v_weight = torch.where(v_error > 0, _expectile, 1.0 - _expectile)\n    v_loss_unclipped = v_weight * v_error.pow(2)\n    if args.clip_vloss:\n        v_clipped = mb_values + torch.clamp(newvalue - mb_values, -args.clip_coef, args.clip_coef)\n        v_error_clipped = mb_returns - v_clipped\n        v_weight_clipped = torch.where(v_error_clipped > 0, _expectile, 1.0 - _expectile)\n        v_loss_clipped = v_weight_clipped * v_error_clipped.pow(2)\n        v_loss = 0.5 * torch.max(v_loss_unclipped, v_loss_clipped).mean()\n    else:\n        v_loss = 0.5 * v_loss_unclipped.mean()\n\n    entropy_loss = entropy.mean()\n    loss = pg_loss - args.ent_coef * entropy_loss + v_loss * args.vf_coef\n    return loss, pg_loss, v_loss, entropy_loss, approx_kl, clipfrac",
5  "after_line": 174,
6  "start_line": 175,
7  "end_line": 219
8}
Tool ResultStep 1
OK: Replaced lines 175..219 with 97 line(s) in cleanrl/cleanrl/custom_onpolicy_continuous.py. Editable range: 175–273.

[Current file: cleanrl/cleanrl/custom_onpolicy_continuous.py | editable: 175–273 | total: 438 lines]
   172|     # =================================================================
   173|     # EDITABLE: get_action_and_value and compute_losses
   174|     # =================================================================
   175      def get_action_and_value(self, obs, action=None):
   176          """Bounded Gaussian policy with boundary-aware exploration.
   177  
   178          We sample in an unconstrained space and squash with tanh so that the
   179          policy matches the Box action bounds more faithfully than an
   180          unsquashed Gaussian followed by environment-side clipping.
   181          Additionally, the exploration scale is reduced near saturated means,
   182          which improves stability for precise-control regimes.
   183          
AssistantStep 2test
Tool Input
1{
2  "is_final": false,
3  "use_last": false
4}
AssistantStep 2test
Tool Input
1{
2  "is_final": false,
3  "use_last": false
4}
Tool ResultStep 2
## Seed 42

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=0.0007 vf_loss=0.0386 entropy=0.3658 approx_kl=0.0045 clipfrac=0.0039
TRAIN_METRICS step=993280 pg_loss=0.0009 vf_loss=0.0032 entropy=0.3660 approx_kl=0.0026 clipfrac=0.0025
TRAIN_METRICS step=995328 pg_loss=-0.0042 vf_loss=0.0102 entropy=0.3662 approx_kl=0.0011 clipfrac=0.0000
TRAIN_METRICS step=997376 pg_loss=-0.0382 vf_loss=0.0441 entropy=0.3662 approx_kl=0.0002 clipfrac=0.0000
TRAIN_METRICS step=999424 pg_loss=-0.0370 vf_loss=0.0151 entropy=0.3663 approx_kl=0.0001 clipfrac=0.0000
Evaluation (halfcheetah-v4):
Eval episodic_return: 3644.05
Eval episodic_return: 3697.78
Eval episodic_return: 3724.79
Final eval return: 3724.79

### swimmer-v4 (scripts/swimmer.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0077 vf_loss=0.0006 entropy=0.4932 approx_kl=0.0006 clipfrac=0.0000
TRAIN_METRICS step=993280 pg_loss=-0.0193 vf_loss=0.0134 entropy=0.493
AssistantStep 3test
Tool Input
1{
2  "is_final": true,
3  "use_last": true
4}
Tool ResultStep 3
## Seed 42

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=0.0007 vf_loss=0.0386 entropy=0.3658 approx_kl=0.0045 clipfrac=0.0039
TRAIN_METRICS step=993280 pg_loss=0.0009 vf_loss=0.0032 entropy=0.3660 approx_kl=0.0026 clipfrac=0.0025
TRAIN_METRICS step=995328 pg_loss=-0.0042 vf_loss=0.0102 entropy=0.3662 approx_kl=0.0011 clipfrac=0.0000
TRAIN_METRICS step=997376 pg_loss=-0.0382 vf_loss=0.0441 entropy=0.3662 approx_kl=0.0002 clipfrac=0.0000
TRAIN_METRICS step=999424 pg_loss=-0.0370 vf_loss=0.0151 entropy=0.3663 approx_kl=0.0001 clipfrac=0.0000
Evaluation (halfcheetah-v4):
Eval episodic_return: 3644.05
Eval episodic_return: 3697.78
Eval episodic_return: 3724.79
Final eval return: 3724.79

### swimmer-v4 (scripts/swimmer.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0077 vf_loss=0.0006 entropy=0.4932 approx_kl=0.0006 clipfrac=0.0000
TRAIN_METRICS step=993280 pg_loss=-0.0193 vf_loss=0.0134 entropy=0.493
Tool ResultStep 2
## Seed 42

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0781 vf_loss=0.0403 entropy=-12.5865 approx_kl=0.0055 clipfrac=0.0592
TRAIN_METRICS step=993280 pg_loss=-0.1455 vf_loss=0.0053 entropy=-12.2236 approx_kl=0.0071 clipfrac=0.0335
TRAIN_METRICS step=995328 pg_loss=-0.1641 vf_loss=0.0027 entropy=-13.0960 approx_kl=0.0053 clipfrac=0.0207
TRAIN_METRICS step=997376 pg_loss=-0.2063 vf_loss=0.0021 entropy=-12.6160 approx_kl=0.0037 clipfrac=0.0155
TRAIN_METRICS step=999424 pg_loss=-0.1292 vf_loss=0.0037 entropy=-13.3222 approx_kl=0.0003 clipfrac=0.0000
Evaluation (halfcheetah-v4):
Eval episodic_return: 1558.61
Eval episodic_return: 1576.07
Eval episodic_return: 1573.43
Final eval return: 1573.43

### swimmer-v4 (scripts/swimmer.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.1553 vf_loss=0.0000 entropy=-4.7232 approx_kl=0.0022 clipfrac=0.0457
TRAIN_METRICS step=993280 pg_loss=-0.2231 vf_loss=0.0000 
AssistantStep 3test
Tool Input
1{
2  "is_final": true,
3  "use_last": true
4}
Tool ResultStep 3
## Seed 42

### halfcheetah-v4 (scripts/halfcheetah.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.0781 vf_loss=0.0403 entropy=-12.5865 approx_kl=0.0055 clipfrac=0.0592
TRAIN_METRICS step=993280 pg_loss=-0.1455 vf_loss=0.0053 entropy=-12.2236 approx_kl=0.0071 clipfrac=0.0335
TRAIN_METRICS step=995328 pg_loss=-0.1641 vf_loss=0.0027 entropy=-13.0960 approx_kl=0.0053 clipfrac=0.0207
TRAIN_METRICS step=997376 pg_loss=-0.2063 vf_loss=0.0021 entropy=-12.6160 approx_kl=0.0037 clipfrac=0.0155
TRAIN_METRICS step=999424 pg_loss=-0.1292 vf_loss=0.0037 entropy=-13.3222 approx_kl=0.0003 clipfrac=0.0000
Evaluation (halfcheetah-v4):
Eval episodic_return: 1558.61
Eval episodic_return: 1576.07
Eval episodic_return: 1573.43
Final eval return: 1573.43

### swimmer-v4 (scripts/swimmer.sh)
Training metrics (last steps):
TRAIN_METRICS step=991232 pg_loss=-0.1553 vf_loss=0.0000 entropy=-4.7232 approx_kl=0.0022 clipfrac=0.0457
TRAIN_METRICS step=993280 pg_loss=-0.2231 vf_loss=0.0000 
AssistantStep 1edit
Tool Input
1{
2  "op": "replace",
3  "filename": "cleanrl/cleanrl/custom_onpolicy_continuous.py",
4  "content": "    def get_action_and_value(self, obs, action=None):\n        # Action-bound-aware policy: tanh-squashed Gaussian.\n        # This removes the train/eval mismatch caused by environment-side clipping.\n        action_mean = self.actor_mean(obs)\n        action_logstd = self.actor_logstd.expand_as(action_mean).clamp(-5.0, 1.0)\n        action_std = torch.exp(action_logstd)\n        probs = Normal(action_mean, action_std)\n        eps = 1e-6\n\n        if action is None:\n            pre_tanh_action = probs.rsample()\n            action = torch.tanh(pre_tanh_action)\n        else:\n            action = action.clamp(-1.0 + eps, 1.0 - eps)\n            pre_tanh_action = 0.5 * (torch.log1p(action) - torch.log1p(-action))\n\n        logprob = probs.log_prob(pre_tanh_action) - torch.log(1.0 - action.pow(2) + eps)\n        logprob = logprob.sum(1)\n\n        # Exact entropy is intractable after squashing; base Gaussian entropy works\n        # well enough here and keeps the objective simple.\n        entropy = probs.entropy().sum(1)\n        return action, logprob, entropy, self.critic(obs)\n\n\ndef compute_losses(agent, mb_obs, mb_actions, mb_logprobs, mb_advantages, mb_returns, mb_values, args):\n    \"\"\"Asymmetric clipped PPO with positive-advantage regression and expectile value fitting.\n\n    Key ideas:\n    1) tanh-squashed Gaussian policy for action-bound awareness,\n    2) asymmetric PPO clipping: larger trust region for positive advantages,\n       tighter clipping for negative advantages,\n    3) small positive-advantage regression bonus (AWR-style) to reinforce strong actions,\n    4) clipped expectile critic to correct underestimation faster than overestimation.\n    \"\"\"\n    _pos_clip_mult = 1.5\n    _neg_clip_mult = 0.5\n    _awr_beta = 1.5\n    _awr_max_weight = 3.0\n    _awr_coef = 0.05\n    _trust_coef = 0.02\n    _expectile = 0.6\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 clipped surrogate: reinforce good actions more aggressively,\n    # but damp noisy penalties on bad actions.\n    pos_clipped_ratio = torch.clamp(ratio, 1.0 - args.clip_coef, 1.0 + args.clip_coef * _pos_clip_mult)\n    neg_clipped_ratio = torch.clamp(ratio, 1.0 - args.clip_coef * _neg_clip_mult, 1.0 + args.clip_coef)\n    clipped_ratio = torch.where(mb_advantages >= 0, pos_clipped_ratio, neg_clipped_ratio)\n    surrogate = torch.min(ratio * mb_advantages, clipped_ratio * mb_advantages)\n    ppo_loss = -surrogate.mean()\n\n    # Positive-advantage regression bonus: pushes probability mass toward the\n    # best sampled actions without letting a few outliers dominate.\n    with torch.no_grad():\n        pos_adv = torch.relu(mb_advantages)\n        awr_weight = torch.exp(pos_adv / _awr_beta) - 1.0\n        awr_weight = torch.clamp(awr_weight, max=_awr_max_weight)\n    regression_loss = -(awr_weight * newlogprob).mean()\n\n    # Mild ratio regularizer because the regression bonus bypasses PPO clipping.\n    trust_loss = (logratio.pow(2)).mean()\n    pg_loss = ppo_loss + _awr_coef * regression_loss + _trust_coef * trust_loss\n\n    # Clipped expectile critic: adapt faster when returns exceed current values,\n    # while retaining PPO-style value clipping for stability.\n    newvalue = newvalue.view(-1)\n    value_error = mb_returns - newvalue\n    value_weight = torch.where(value_error > 0, _expectile, 1.0 - _expectile)\n    v_loss_unclipped = value_weight * value_error.pow(2)\n    if args.clip_vloss:\n        v_clipped = mb_values + torch.clamp(newvalue - mb_values, -args.clip_coef, args.clip_coef)\n        clipped_error = mb_returns - v_clipped\n        clipped_weight = torch.where(clipped_error > 0, _expectile, 1.0 - _expectile)\n        v_loss_clipped = clipped_weight * clipped_error.pow(2)\n        v_loss = 0.5 * torch.max(v_loss_unclipped, v_loss_clipped).mean()\n    else:\n        v_loss = 0.5 * v_loss_unclipped.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",
5  "after_line": 174,
6  "start_line": 175,
7  "end_line": 219
8}