README.md

---
title: Physics-Informed Bayesian Optimization
emoji: ⚗️
colorFrom: blue
colorTo: green
sdk: gradio
sdk_version: "5.23.0"
app_file: app.py
pinned: true
license: mit
tags:
  - bayesian-optimization
  - physics-informed
  - experiment-design
  - materials-science
  - gaussian-process
---

# Physics-Informed Bayesian Optimization Platform (PIBO)

A platform for designing experiments using physics-informed surrogate models with Bayesian optimization. The core idea: **use physical models as structured priors for Gaussian Processes**, so the GP learns residuals between physics predictions and real observations, dramatically improving sample efficiency.

## Architecture

```
physics_informed_bo/
├── config.py                    # Configuration classes
├── models/                      # Surrogate models
│   ├── base.py                  # Abstract base class
│   ├── physics_model.py         # Physics model wrapper + GPyTorch mean function
│   ├── gp_model.py              # Standard GP & Physics-Informed GP
│   ├── hybrid_model.py          # Hybrid surrogate (physics + GP)
│   └── multi_fidelity.py        # Multi-fidelity model (physics=low, data=high)
├── priors/                      # Prior management
│   ├── data_prior.py            # Initial data management
│   ├── physics_prior.py         # Physics model + constraints
│   └── prior_manager.py         # Orchestrates prior combination
├── optimizers/                  # Optimizer backends
│   ├── base_optimizer.py        # Abstract optimizer
│   ├── botorch_optimizer.py     # BoTorch backend (primary)
│   ├── ax_optimizer.py          # AX Platform backend
│   ├── bofire_optimizer.py      # BoFire backend
│   └── factory.py               # Optimizer factory
├── experiment/                  # Experiment design
│   ├── parameter_space.py       # Parameter space definitions
│   ├── designer.py              # Main experiment designer API
│   └── campaign.py              # Full campaign management
├── utils/                       # Utilities
│   ├── visualization.py         # Plotting functions
│   └── diagnostics.py           # Model diagnostics
└── examples/                    # Usage examples
    ├── minimal_example.py       # Quick start (~30 lines)
    ├── polymer_optimization.py  # Full polymer design example
    └── multi_fidelity_example.py
```

## Core Concept

Traditional BO uses a GP with a constant or zero mean function. This platform replaces that with a **physics model as the GP mean function**:

```
f(x) = physics_model(x) + GP_residual(x)
```

Where `GP_residual ~ GP(0, k(x,x'))` only needs to learn the discrepancy between physics and reality. Benefits:

1. **Sample efficiency**: Physics captures the trend, GP only needs to learn deviations
2. **Extrapolation**: Physics model provides reasonable predictions outside observed data
3. **Constraint awareness**: Physical constraints are naturally incorporated
4. **Graceful degradation**: System works with physics-only (no data), hybrid, or GP-only modes

## Quick Start

```python
import torch
from physics_informed_bo import ExperimentDesigner, ParameterSpace

# Define your physics model
def my_physics_model(X):
    temp, pressure = X[:, 0], X[:, 1]
    return torch.exp(-5000 / temp) * pressure**0.5

# Define parameter space
space = ParameterSpace()
space.add_continuous("temperature", 300, 600, units="K")
space.add_continuous("pressure", 1, 50, units="bar")

# Create designer with physics + initial data
designer = ExperimentDesigner(
    parameter_space=space,
    physics_fn=my_physics_model,
    initial_data=(X_init, y_init),  # Your initial experiments
)

# Get next experiment suggestions
next_experiments = designer.suggest(n=3)

# After running experiments, update
designer.update(X_new, y_new)
```

## Full Campaign Example

```python
from physics_informed_bo import OptimizationCampaign, ParameterSpace
from physics_informed_bo.config import OptimizationConfig, AcquisitionType

config = OptimizationConfig(
    acquisition_type=AcquisitionType.PHYSICS_INFORMED_EI,
    max_iterations=30,
)

campaign = OptimizationCampaign(
    name="my_experiment",
    parameter_space=space,
    physics_fn=my_physics_model,
    initial_data=(X_init, y_init),
    config=config,
)

# Automated loop
results = campaign.run_automated(objective_fn=run_experiment)

# Or human-in-the-loop
suggestion = campaign.suggest_next()
# ... run experiment manually ...
campaign.report_result(suggestion[0], measured_value)
```

## Surrogate Model Modes

The platform automatically selects the best mode based on available information:

| Data Available | Physics Model | Mode Selected | Description |
|---|---|---|---|
| None | Yes | `physics_only` | Pure physics predictions |
| < 20 points | Yes | `physics_as_mean` | Physics as GP mean, GP learns residual |
| 20-50 points | Yes | `weighted_ensemble` | Adaptive weighting of physics + GP |
| Any | No | `gp_only` | Standard GP (data-driven only) |

## Optimizer Backends

### BoTorch (Default)
- Full BoTorch acquisition function suite (EI, UCB, KG, NEI)
- Custom `PhysicsInformedEI` that penalizes physically implausible regions
- Batch optimization support

### AX Platform
- Structured experiment management
- Human-in-the-loop support
- Trial tracking and analysis

### BoFire
- Chemistry/materials-focused features
- Mixture constraints (sum-to-one)
- Multi-objective optimization
- Categorical and molecular parameters

## Physics Constraints

```python
from physics_informed_bo.priors import PhysicsPrior

physics = PhysicsPrior(physics_fn=my_model)

# Add thermodynamic constraint
physics.add_constraint(
    name="gibbs_feasibility",
    constraint_fn=lambda X: compute_gibbs(X),  # <=0 is feasible
    constraint_type="inequality",
)

# Add mass balance constraint
physics.add_constraint(
    name="mass_balance",
    constraint_fn=lambda X: X.sum(dim=-1) - 1.0,  # ==0
    constraint_type="equality",
)
```

## Installation

```bash
pip install torch gpytorch botorch numpy pandas matplotlib

# Optional backends
pip install ax-platform  # For AX
pip install bofire        # For BoFire
```

## Key Dependencies

- **PyTorch**: Tensor computation and autograd
- **GPyTorch**: Gaussian Process models
- **BoTorch**: Bayesian optimization acquisition functions
- **AX Platform** (optional): Experiment management
- **BoFire** (optional): Chemistry-focused BO