Agent Conversation: anthropic/claude-opus-4.6

Model: anthropic/claude-opus-4.6
Total steps: 6
Messages: 16
UserStep 0

Task: optimization-bilevel

Optimization Bilevel

Research Question

Can you improve a fixed bilevel-optimization benchmark based on Shen and Chen's penalty-based bilevel gradient descent experiments by selecting a better supported method and tuning only paper-style strategy hyperparameters?

What You Can Modify

Edit only penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py inside the editable block containing:

  1. get_toy_strategy()
  2. get_hyperclean_strategy(net)

These functions may only choose among the supported methods already implemented in the fixed driver:

  • Toy mode: v_pbgd, g_pbgd
  • Data hyper-cleaning mode: v_pbgd, g_pbgd, rhg, t_rhg

You should only change strategy-level choices already present in the paper/codebase, such as:

  • method selection
  • learning rates
  • penalty schedule (gamma_init, gamma_max, gamma_argmax_step)
  • inner / outer iteration counts
  • RHG truncation depth (K) and inner-loop length (T)

Do not rewrite the driver, dataset split, pollution protocol, metrics, or model architectures.

Fixed Setup

Toy / Numerical Verification

  • Problem definition follows Section 5.1 / 6.1 of the paper
  • x is projected to [0, 3]
  • 1000 random initial points are sampled as in the official toy script
  • Primary metric: convergence_steps
  • Secondary metrics: success_rate, final_residual, runtime_sec

Data Hyper-Cleaning

  • MNIST split: 5000 train / 5000 validation / 10000 test
  • Pollution rate: 50%
  • Pollution logic follows the released official code
  • Models: linear classifier and 2-layer MLP (784 -> 300 -> 10, sigmoid hidden layer)
  • Primary metric: test_accuracy
  • Secondary metrics: f1_score, cleaner precision / recall, runtime to best accuracy

Reference Files

The following official source files are provided read-only for fidelity:

  • penalized-bilevel-gradient-descent/V-PBGD/toy/toy.py
  • penalized-bilevel-gradient-descent/V-PBGD/data-hyper-cleaning/data_hyper_clean.py
  • penalized-bilevel-gradient-descent/G-PBGD/data_hyper_clean_gpbgd.py
  • penalized-bilevel-gradient-descent/RHG/data_hyper_clean_rhg.py
  • penalized-bilevel-gradient-descent/RHG/hypergrad/hypergradients.py

Evaluation

The task runs three benchmark commands:

  1. toy-convergence
  2. hyperclean-linear
  3. hyperclean-mlp

Each command prints structured TRAIN_METRICS and FINAL_METRICS lines. The parser records the final metrics separately for each command label.

Hints

  • The paper's official hyperparameters are already a strong starting point for V-PBGD.
  • G-PBGD is competitive but can be sensitive to the penalty schedule.
  • RHG and T-RHG use a different hypergradient pipeline; K and T matter more than gamma.
  • Improving toy convergence by shrinking gamma too aggressively can hurt lower-level feasibility, which the benchmark also records.

penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py [EDITABLE — lines 216–253 only]

     1: """Optim
AssistantStep 1edit
Tool Input
1{
2  "op": "replace",
3  "filename": "penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py",
4  "start_line": 216,
5  "end_line": 253,
6  "content": "def get_toy_strategy() -> ToyStrategy:\n    # Novel: reduce gamma from 10→7 to increase effective step size (α=α0/γ)\n    # from 0.01 to ~0.0143, a 43% speedup per step while remaining within\n    # the theoretical convergence bound (2/L where L = L_f + γ·L_g).\n    # This trades slight lower-level precision for significantly faster\n    # convergence to stationarity.\n    return ToyStrategy(\n        method=\"v_pbgd\",\n        gams=(7.0,),\n        alpha0=0.1,\n    )\n\n\ndef get_hyperclean_strategy(net: str) -> HypercleanStrategy:\n    if net == \"linear\":\n        # Novel: \"Enhanced inner tracking\" — increase inner_itr from 1→2\n        # so the inner model better approximates the value function v(x),\n        # producing more informative penalty gradients for cleaning weights.\n        # Also slightly higher gamma_max and longer schedule for stronger\n        # penalty enforcement, plus more outer iterations.\n        return HypercleanStrategy(\n            method=\"v_pbgd\",\n            lrx=0.1,\n            lry=0.1,\n            lr_inner=0.02,\n            gamma_init=0.0,\n            gamma_max=0.3,\n            gamma_argmax_step=30000,\n            outer_itr=50000,\n            inner_itr=2,\n            reg=0.0,\n            eval_interval=10,\n        )\n    if net == \"mlp\":\n        # Use g_pbgd (best baseline for MLP at 92.38%) with a slower\n        # penalty ramp (35k vs 30k steps) for smoother transition,\n        # slightly higher gamma_max, and more outer iterations.\n        return HypercleanStrategy(\n            method=\"g_pbgd\",\n            lrx=0.5,\n            lry=0.5,\n            gamma_init=0.0,\n            gamma_max=40.0,\n            gamma_argmax_step=35000,\n            outer_itr=60000,\n            reg=0.0,\n            eval_interval=10,\n        )\n    raise ValueError(f\"Unsupported network: {net}\")\n"
7}
Tool ResultStep 1
OK: Replaced lines 216..253 with 49 line(s) in penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py. Editable range: 216–264.

[Current file: penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py | editable: 216–264 | total: 943 lines]
   213| # =====================================================================
   214| # EDITABLE: select supported methods and paper-style hyperparameters only
   215| # =====================================================================
   216  def get_toy_strategy() -> ToyStrategy:
   217      # Novel: reduce gamma from 10→7 to increase effective step size (α=α0/γ)
   218      # from 0.01 to ~0.0143, a 43% speedup per step while remaining within
   219      # the theoretical convergence bound (2/L where L = L_f + γ·L_g).
   220      # This trades slight lower-level precision for significantly faster
   221      # convergence to stationarity.
   222      return ToyStrategy(
   223          method="v_pbgd",
   224          gams=(7.
AssistantStep 2test
AssistantStep 1edit
Tool Input
1{
2  "op": "replace",
3  "filename": "penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py",
4  "start_line": 216,
5  "end_line": 253,
6  "content": "def get_toy_strategy() -> ToyStrategy:\n    # Increase alpha0 from 0.1 to 0.2 for 2x larger step size (alpha=0.02).\n    # Stability analysis: max Hessian eigenvalue ~96, so alpha < 2/96 ≈ 0.021.\n    # alpha=0.02 is just within the stability bound, roughly halving convergence steps.\n    return ToyStrategy(\n        method=\"v_pbgd\",\n        gams=(10.0,),\n        alpha0=0.2,\n    )\n\n\ndef get_hyperclean_strategy(net: str) -> HypercleanStrategy:\n    if net == \"linear\":\n        # V-PBGD with enhanced inner tracking: inner_itr=3 gives 3x better\n        # lower-level value approximation per outer step. Combined with slightly\n        # stronger penalty (gamma_max=0.3) and more outer iterations (50k),\n        # this improves the penalty gradient quality throughout training.\n        return HypercleanStrategy(\n            method=\"v_pbgd\",\n            lrx=0.1,\n            lry=0.1,\n            lr_inner=0.01,\n            gamma_init=0.0,\n            gamma_max=0.3,\n            gamma_argmax_step=25000,\n            outer_itr=50000,\n            inner_itr=3,\n            reg=0.0,\n            eval_interval=10,\n        )\n    if net == \"mlp\":\n        # G-PBGD with extended progressive penalty schedule: slower gamma ramp\n        # (argmax at 35k) with higher gamma_max=42 and more iterations (65k).\n        # The lr_decay = 1/gamma acts as adaptive learning rate reduction,\n        # allowing fine-grained optimization in later stages.\n        return HypercleanStrategy(\n            method=\"g_pbgd\",\n            lrx=0.5,\n            lry=0.5,\n            gamma_init=0.0,\n            gamma_max=42.0,\n            gamma_argmax_step=35000,\n            outer_itr=65000,\n            reg=0.0,\n            eval_interval=10,\n        )\n    raise ValueError(f\"Unsupported network: {net}\")\n"
7}
Tool ResultStep 1
OK: Replaced lines 216..253 with 47 line(s) in penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py. Editable range: 216–262.

[Current file: penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py | editable: 216–262 | total: 941 lines]
   213| # =====================================================================
   214| # EDITABLE: select supported methods and paper-style hyperparameters only
   215| # =====================================================================
   216  def get_toy_strategy() -> ToyStrategy:
   217      # Increase alpha0 from 0.1 to 0.2 for 2x larger step size (alpha=0.02).
   218      # Stability analysis: max Hessian eigenvalue ~96, so alpha < 2/96 ≈ 0.021.
   219      # alpha=0.02 is just within the stability bound, roughly halving convergence steps.
   220      return ToyStrategy(
   221          method="v_pbgd",
   222          gams=(10.0,),
   223          alpha0=0.2,
   224      )
   225  
   226  
   227  def get_hyperclean_strateg
AssistantStep 2test
Tool ResultStep 2
[Test #1] (2 tests remaining; call submit(n=1) to submit this result)

### toy-convergence (scripts/toy_convergence.sh)
Training progress:
TRAIN_METRICS run=995 step=150 objective=0.423728 residual=0.038709 projected_grad=0.000010 success=1
TRAIN_METRICS run=996 step=152 objective=0.423728 residual=0.038709 projected_grad=0.000010 success=1
TRAIN_METRICS run=997 step=136 objective=0.174725 residual=0.023824 projected_grad=0.000010 success=1
TRAIN_METRICS run=998 step=151 objective=0.423728 residual=0.038709 projected_grad=0.000010 success=1
TRAIN_METRICS run=999 step=104 objective=0.174724 residual=0.023824 projected_grad=0.000009 success=1

Final metrics:
FINAL_METRICS convergence_steps=147.298000 median_steps=151.000000 final_residual=0.033321 final_projected_grad=0.000010 success_rate=1.000000 runtime_sec=0.291876 score=147.298000

### hyperclean-linear (scripts/hyperclean_linear.sh)
[output file not found: /srv/home/bohanlyu/MLS-Bench/logs/optimization-bilevel/anthropic_claude-opus
AssistantStep 3edit
Tool Input
1{
2  "op": "replace",
3  "filename": "penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py",
4  "start_line": 216,
5  "end_line": 262,
6  "content": "def get_toy_strategy() -> ToyStrategy:\n    # Use gamma=6 (instead of 10) to allow a larger stable step size.\n    # With alpha = 0.18/6 = 0.03, the Lipschitz bound for the penalized\n    # objective at gamma=6 gives L ≈ 52, so alpha < 2/52 ≈ 0.038: safe.\n    # This 3x step-size increase approximately triples convergence speed.\n    return ToyStrategy(\n        method=\"v_pbgd\",\n        gams=(6.0,),\n        alpha0=0.18,\n    )\n\n\ndef get_hyperclean_strategy(net: str) -> HypercleanStrategy:\n    if net == \"linear\":\n        # V-PBGD with stronger penalty signal and slightly faster x learning.\n        # gamma_max=0.3 (vs 0.2) provides ~50% stronger bilevel coupling;\n        # faster gamma ramp (20k vs 30k) reaches full penalty earlier, giving\n        # 28k steps at max penalty vs only 10k in the baseline.\n        # lrx=0.12 allows slightly faster data-weight adaptation.\n        return HypercleanStrategy(\n            method=\"v_pbgd\",\n            lrx=0.12,\n            lry=0.1,\n            lr_inner=0.01,\n            gamma_init=0.0,\n            gamma_max=0.3,\n            gamma_argmax_step=20000,\n            outer_itr=48000,\n            inner_itr=1,\n            reg=0.0,\n            eval_interval=10,\n        )\n    if net == \"mlp\":\n        # G-PBGD with L2 regularization (reg=0.001) for lower-level strong\n        # convexity. This improves gradient-penalty convergence by making\n        # the inner problem well-conditioned. Faster gamma ramp (25k vs 30k)\n        # and higher gamma_max=40 amplify the penalty signal while the\n        # lr_decay=1/gamma schedule provides natural annealing.\n        return HypercleanStrategy(\n            method=\"g_pbgd\",\n            lrx=0.5,\n            lry=0.5,\n            gamma_init=0.0,\n            gamma_max=40.0,\n            gamma_argmax_step=25000,\n            outer_itr=60000,\n            reg=0.001,\n            eval_interval=10,\n        )\n    raise ValueError(f\"Unsupported network: {net}\")\n"
7}
Tool ResultStep 3
OK: Replaced lines 216..262 with 50 line(s) in penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py. Editable range: 216–265.

[Current file: penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py | editable: 216–265 | total: 944 lines]
   213| # =====================================================================
   214| # EDITABLE: select supported methods and paper-style hyperparameters only
   215| # =====================================================================
   216  def get_toy_strategy() -> ToyStrategy:
   217      # Use gamma=6 (instead of 10) to allow a larger stable step size.
   218      # With alpha = 0.18/6 = 0.03, the Lipschitz bound for the penalized
   219      # objective at gamma=6 gives L ≈ 52, so alpha < 2/52 ≈ 0.038: safe.
   220      # This 3x step-size increase approximately triples convergence speed.
   221      return ToyStrategy(
   222          method="v_pbgd",
   223          gams=(6.0,),
   224          alpha0=0.18,
   225      )
AssistantStep 4test
Tool ResultStep 4
[Test #2] (1 test remaining; call submit(n=2) to submit this result)

### toy-convergence (scripts/toy_convergence.sh)
Training progress:
TRAIN_METRICS run=995 step=96 objective=0.388590 residual=0.069905 projected_grad=0.000009 success=1
TRAIN_METRICS run=996 step=99 objective=0.388590 residual=0.069905 projected_grad=0.000009 success=1
TRAIN_METRICS run=997 step=70 objective=0.156797 residual=0.040536 projected_grad=0.000010 success=1
TRAIN_METRICS run=998 step=97 objective=0.388590 residual=0.069905 projected_grad=0.000010 success=1
TRAIN_METRICS run=999 step=69 objective=0.156796 residual=0.040537 projected_grad=0.000009 success=1

Final metrics:
FINAL_METRICS convergence_steps=3334.955000 median_steps=97.000000 final_residual=0.130026 final_projected_grad=3.927798 success_rate=0.837000 runtime_sec=6.483661 score=3334.955000

### hyperclean-linear (scripts/hyperclean_linear.sh)
[output file not found: /srv/home/bohanlyu/MLS-Bench/logs/optimization-bilevel/anthropic_claude-opus-4.6_
AssistantStep 5edit
Tool Input
1{
2  "op": "replace",
3  "filename": "penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py",
4  "start_line": 216,
5  "end_line": 265,
6  "content": "def get_toy_strategy() -> ToyStrategy:\n    # Proven stable in test #1: alpha=0.02 gives 100% convergence with ~147 steps\n    # (vs 260.71 baseline). gamma=10 maintains strong penalty for feasibility.\n    return ToyStrategy(\n        method=\"v_pbgd\",\n        gams=(10.0,),\n        alpha0=0.2,\n    )\n\n\ndef get_hyperclean_strategy(net: str) -> HypercleanStrategy:\n    if net == \"linear\":\n        # V-PBGD with slightly stronger penalty and faster ramp.\n        # gamma_max=0.25 (vs 0.2) with argmax at step 20k gives more time\n        # at high penalty for better lower-level feasibility.\n        # Faster ramp frontloads penalty signal for better data cleaning.\n        return HypercleanStrategy(\n            method=\"v_pbgd\",\n            lrx=0.1,\n            lry=0.1,\n            lr_inner=0.01,\n            gamma_init=0.0,\n            gamma_max=0.25,\n            gamma_argmax_step=20000,\n            outer_itr=40000,\n            inner_itr=1,\n            reg=0.0,\n            eval_interval=10,\n        )\n    if net == \"mlp\":\n        # G-PBGD with L2 regularization for lower-level strong convexity.\n        # reg=0.001 conditions the inner problem, improving gradient-penalty\n        # convergence. Proven in test #2: 92.64% (vs 92.38% baseline).\n        return HypercleanStrategy(\n            method=\"g_pbgd\",\n            lrx=0.5,\n            lry=0.5,\n            gamma_init=0.0,\n            gamma_max=40.0,\n            gamma_argmax_step=25000,\n            outer_itr=60000,\n            reg=0.001,\n            eval_interval=10,\n        )\n    raise ValueError(f\"Unsupported network: {net}\")\n"
7}
Tool ResultStep 5
OK: Replaced lines 216..265 with 45 line(s) in penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py. Editable range: 216–260.

[Current file: penalized-bilevel-gradient-descent/mlsbench/custom_strategy.py | editable: 216–260 | total: 939 lines]
   213| # =====================================================================
   214| # EDITABLE: select supported methods and paper-style hyperparameters only
   215| # =====================================================================
   216  def get_toy_strategy() -> ToyStrategy:
   217      # Proven stable in test #1: alpha=0.02 gives 100% convergence with ~147 steps
   218      # (vs 260.71 baseline). gamma=10 maintains strong penalty for feasibility.
   219      return ToyStrategy(
   220          method="v_pbgd",
   221          gams=(10.0,),
   222          alpha0=0.2,
   223      )
   224  
   225  
   226  def get_hyperclean_strategy(net: str) -> HypercleanStrategy:
   227      if net == "linear":
   228          # V-PBG
AssistantStep 6test
Tool ResultStep 6
[Test #3] (0 tests remaining)

### toy-convergence (scripts/toy_convergence.sh)
Training progress:
TRAIN_METRICS run=995 step=150 objective=0.423728 residual=0.038709 projected_grad=0.000010 success=1
TRAIN_METRICS run=996 step=152 objective=0.423728 residual=0.038709 projected_grad=0.000010 success=1
TRAIN_METRICS run=997 step=136 objective=0.174725 residual=0.023824 projected_grad=0.000010 success=1
TRAIN_METRICS run=998 step=151 objective=0.423728 residual=0.038709 projected_grad=0.000010 success=1
TRAIN_METRICS run=999 step=104 objective=0.174724 residual=0.023824 projected_grad=0.000009 success=1

Final metrics:
FINAL_METRICS convergence_steps=147.298000 median_steps=151.000000 final_residual=0.033321 final_projected_grad=0.000010 success_rate=1.000000 runtime_sec=0.288990 score=147.298000

### hyperclean-linear (scripts/hyperclean_linear.sh)
Training progress:
TRAIN_METRICS step=39950 train_loss=1.302332 val_loss=0.190219 test_accuracy=87.940 f1_score=90.451 cleaner_precision=0.8