---
license: apache-2.0
library_name: transformers
tags:
- custom_generate
- sampling
---


# DeepCONF Custom Generation Strategy

This repository implements the DeepCONF (Deep Confidence-based Early Stopping) generation strategy for Hugging Face Transformers models, following the [Deep Think with Confidence](https://jiaweizzhao.github.io/deepconf/) approach from the paper [Deep Think with Confidence](https://huggingface.co/papers/2508.15260).

## Overview

DeepCONF monitors the confidence of generated tokens and stops generation when confidence falls below a threshold. The confidence is calculated as the negative mean log probability of the top-k tokens from the full vocabulary (before sampling/filtering is applied), following the methodology from the [official DeepConf implementation](https://github.com/facebookresearch/deepconf).

## Parameters

- `enable_conf` (bool): Whether to enable the DeepCONF strategy. Defaults to `False`.
- `enable_early_stopping` (bool): Whether to apply early stopping during generation (online mode) or just track confidences for post-processing (batch mode). Defaults to `True`.
- `window_size` (int): Size of the sliding window for confidence calculation. Defaults to `2048`.
- `threshold` (float): Confidence threshold for early stopping. Defaults to `17.0`.
- `conf_topk` (int): Number of top tokens to use for confidence calculation from the full vocabulary. Defaults to `20`.
- `output_confidences` (bool): If `True` and `return_dict_in_generate=True`, returns a per-step confidence tensor alongside generated sequences for debugging/visualization.
- `deepconf_variant` (str): Optional variant for automatic threshold calibration (`"low"` or `"high"`). Requires `deepconf_warmup_confidences`.
- `deepconf_warmup_confidences` (list/tensor): Warmup confidence values for threshold calibration. Used with `deepconf_variant`.
- `deepconf_eta` (float): Optional override for eta value in threshold calculation (defaults: 0.1 for low, 0.9 for high).

## Usage

### Basic Usage

To use this custom generation strategy, you can pass it directly to the `generate` method:

```python
from transformers import AutoModelForCausalLM, AutoTokenizer, GenerationConfig

# Load model and tokenizer
model = AutoModelForCausalLM.from_pretrained(
    "your-model",
    torch_dtype="auto",
    device_map="auto"
)
tokenizer = AutoTokenizer.from_pretrained("your-model")

# Prepare your prompt
question = "What is the square root of 144?"
messages = [{"role": "user", "content": question}]
prompt = tokenizer.apply_chat_template(
    messages,
    tokenize=False,
    add_generation_prompt=True
)
inputs = tokenizer(prompt, return_tensors="pt").to(model.device)

# Configure generation with DeepCONF
gen_config = GenerationConfig(
    do_sample=True,
    temperature=0.7,
    top_p=0.95,
    max_new_tokens=512,
    enable_conf=True,              # Enable DeepCONF
    window_size=2048,              # Sliding window size
    threshold=17.0,                # Confidence threshold
    conf_topk=20,                  # Top-k for confidence (default: 20)
    output_confidences=True,       # Return confidence scores
    return_dict_in_generate=True,  # Required for confidence output
)

# Generate with DeepCONF (Hub repo)
outputs = model.generate(
    **inputs,
    generation_config=gen_config,
    custom_generate="kashif/DeepConf",  # Hugging Face Hub repo
    trust_remote_code=True
)

# Access results
generated_text = tokenizer.decode(outputs.sequences[0], skip_special_tokens=True)
print(f"Generated: {generated_text}")

# Access per-step confidences if requested
if hasattr(outputs, 'confidences'):
    confidences = outputs.confidences  # Shape: (batch_size, num_generated_tokens)
    print(f"Min confidence: {confidences.min().item():.3f}")
    print(f"Mean confidence: {confidences.mean().item():.3f}")
```

### Calibration (DeepConf-low/high)

DeepConf's online stopping threshold can be automatically derived from a warmup phase. This allows you to calibrate the threshold based on actual model behavior rather than using a fixed value.

**Step 1: Warmup Phase** - Generate multiple sequences and collect their minimum confidences:

```python
from transformers import GenerationConfig

# Prepare inputs
question = "What is 2 + 2?"
messages = [{"role": "user", "content": question}]
prompt = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
inputs = tokenizer(prompt, return_tensors="pt").to(model.device)

# Configure warmup generation
warmup_cfg = GenerationConfig(
    do_sample=True,
    temperature=0.7,
    top_p=0.95,
    max_new_tokens=256,
    enable_conf=True,               # Enable confidence tracking
    return_dict_in_generate=True,
    output_confidences=True,
    num_return_sequences=8,         # Generate 8 warmup sequences
    # Note: Do NOT set threshold here - warmup should run without early stopping
)

# Generate warmup sequences
warmup_out = model.generate(
    **inputs,
    generation_config=warmup_cfg,
    custom_generate="kashif/DeepConf",
    trust_remote_code=True,
)

# Extract minimum confidence per sequence (C_t = min over all steps)
warmup_C = warmup_out.confidences.min(dim=1).values.tolist()
print(f"Warmup min confidences: {warmup_C}")
```

**Step 2: Production Generation** - Use warmup confidences to auto-derive threshold:

```python
# Configure production generation with calibrated threshold
gen_cfg = GenerationConfig(
    do_sample=True,
    temperature=0.7,
    top_p=0.95,
    max_new_tokens=512,
    enable_conf=True,
    return_dict_in_generate=True,
    output_confidences=True,

    # Automatic threshold calibration
    deepconf_variant="low",  # "low" (aggressive, 90th percentile) or "high" (permissive, 10th percentile)
    deepconf_warmup_confidences=warmup_C,  # Pass warmup confidences
    # Optional: deepconf_eta=0.1,  # Override eta (defaults: 0.1 for low, 0.9 for high)
)

# Generate with calibrated threshold
outputs = model.generate(
    **inputs,
    generation_config=gen_cfg,
    custom_generate="kashif/DeepConf",
    trust_remote_code=True,
)

print(f"Generated: {tokenizer.decode(outputs.sequences[0], skip_special_tokens=True)}")
```

**Variant Explanation:**
- **DeepConf-low** (eta=0.1): Uses 90th percentile threshold → More aggressive early stopping
- **DeepConf-high** (eta=0.9): Uses 10th percentile threshold → More permissive, allows longer generation

### Two Modes of Operation

DeepConf supports two modes that match different use cases:

#### Mode 1: Online Early Stopping (Default)

This is the default behavior where early stopping happens **during** generation:

```python
# Online mode: Stop immediately when confidence drops
gen_config = GenerationConfig(
    enable_conf=True,
    enable_early_stopping=True,  # Default: True (online stopping)
    threshold=17.0,
    window_size=2048,
    max_new_tokens=512,
)

outputs = model.generate(**inputs, generation_config=gen_config, custom_generate="kashif/DeepConf")
```

**Use cases:**
- Interactive generation where you want immediate results
- Real-time applications
- Single-sequence generation
- Lower memory usage (no need to store full sequences)

#### Mode 2: Batch Generation + Post-Processing

Generate multiple sequences without early stopping, then analyze them afterward:

```python
import torch

# Phase 1: Generate multiple sequences WITHOUT early stopping
gen_config = GenerationConfig(
    enable_conf=True,
    enable_early_stopping=False,  # Disable online stopping
    output_confidences=True,
    return_dict_in_generate=True,
    max_new_tokens=64,
)

# Expand inputs for batch generation (e.g., 8 sequences)
num_sequences = 8
expanded_input_ids = inputs.input_ids.repeat(num_sequences, 1)
if 'attention_mask' in inputs and inputs.attention_mask is not None:
    expanded_attention_mask = inputs.attention_mask.repeat(num_sequences, 1)
else:
    expanded_attention_mask = None

# Generate batch
outputs = model.generate(
    input_ids=expanded_input_ids,
    attention_mask=expanded_attention_mask,
    generation_config=gen_config,
    custom_generate="kashif/DeepConf"
)

# Phase 2: Post-process to analyze confidence patterns
from custom_generate.utils import process_batch_results

results = process_batch_results(
    outputs,
    tokenizer,
    window_size=2048,
    threshold=17.0
)

# Analyze results
print(f"Generated {results['num_traces']} sequences")
print(f"Min confidences: {results['min_confs']}")

for i, trace in enumerate(results['traces']):
    print(f"\nSequence {i+1}:")
    print(f"  Text: {trace['text'][:100]}...")
    print(f"  Min confidence: {trace['min_conf']:.3f}")
    print(f"  Would stop early: {trace['stopped_early']}")
    if trace['stopped_early']:
        print(f"  Stop position: {trace['stop_position']}")
```

**Use cases:**
- Research and experimentation (try different thresholds without regenerating)
- Batch serving (generate multiple candidates at once)
- Analysis and voting (like the official implementation)
- Calibration and threshold tuning

**Utility Functions:**

The `custom_generate/utils.py` module provides helper functions:

- `process_batch_results()`: Analyze batch outputs to detect early stopping positions
- `analyze_early_stopping()`: Calculate statistics on early stopping behavior
- `compute_warmup_threshold()`: Derive threshold from warmup confidences
- `extract_answer()`: Parse LaTeX `\boxed{answer}` patterns

#### Complete Workflow Example (Like Official DeepConf)

This demonstrates the full workflow matching the official implementation:

```python
# Step 1: Warmup phase - generate multiple sequences
warmup_config = GenerationConfig(
    do_sample=True,
    temperature=0.7,
    max_new_tokens=64,
    enable_conf=True,
    enable_early_stopping=False,  # No stopping during warmup
    output_confidences=True,
    return_dict_in_generate=True,
)

# Expand for 8 warmup sequences
num_warmup = 8
expanded_ids = inputs.input_ids.repeat(num_warmup, 1)
expanded_mask = inputs.attention_mask.repeat(num_warmup, 1) if 'attention_mask' in inputs else None

warmup_outputs = model.generate(
    input_ids=expanded_ids,
    attention_mask=expanded_mask,
    generation_config=warmup_config,
    custom_generate="kashif/DeepConf"
)

# Process warmup to get min confidences
from custom_generate.utils import process_batch_results, compute_warmup_threshold

warmup_results = process_batch_results(warmup_outputs, tokenizer, window_size=10)
print(f"Warmup min confidences: {warmup_results['min_confs']}")

# Step 2: Compute threshold from warmup
threshold = compute_warmup_threshold(
    warmup_results['min_confs'],
    variant="low"  # or "high"
)
print(f"Calibrated threshold: {threshold:.3f}")

# Step 3: Final generation with calibrated threshold
final_config = GenerationConfig(
    enable_conf=True,
    enable_early_stopping=True,  # Online stopping with calibrated threshold
    threshold=threshold,
    window_size=10,
    max_new_tokens=128,
)

final_output = model.generate(**inputs, generation_config=final_config, custom_generate="kashif/DeepConf")
print(tokenizer.decode(final_output.sequences[0], skip_special_tokens=True))
```

## Technical Details

### Confidence Calculation

The confidence score for each generated token is calculated as follows:

1. **Extract top-k tokens**: Get the top-k (default: 20) tokens with highest probabilities from the full vocabulary
2. **Compute log probabilities**: Calculate log probabilities for these top-k tokens
3. **Average**: The confidence score is `-mean(log_probs)` of the top-k tokens

This approach:
- Uses the **full probability distribution** (before any top-k/top-p/temperature filtering)
- Always considers a **fixed number of tokens** (conf_topk=20)
- Naturally **includes the sampled token** if it's in the top-k

### Online Stopping

The online method uses a sliding window of confidence scores:
- Maintains a window of the last `window_size` (default: 2048) confidence scores
- Calculates the mean confidence over this window
- Stops generation when: `mean_confidence < threshold`

## Requirements

- PyTorch >= 1.13.0
- Transformers >= 4.35.0