SMKBO 0.0.1

Spectral mixture kernel for Bayesian Optimization

SMKBO: Spectral Mixture Kernel for Bayesian Optimization

This repo contains implementation of the SMKBO algorithm for mixed input variables.

Installation

Dependencies

Python>=3.9
gpytorch>=1.14
pytorch==2.5.1
botorch>=0.14.0
numpy==1.16.4

Option 1: Installing the latest release

The latest release of SMKBO is easily installed via pip:

pip install smkbo

Option 2: Editable install

If you want to contribute to SMKBO, you will want to install editably so that you can change files and have the changes reflected in your local install.

git clone https://github.com/YyyyyyiZ/SMKBO.git

Getting Started

Here's a quick run down of the main components of a Bayesian optimization loop.

1. Import packages

   from SMKBO.test_func import *
   from SMKBO.bo import SpectralBO
   

2. Define your optimization problem

   Option 2a: Mixed problem

   f = Func2C(lamda=1e-6, normalize=False)
   max_iters = 30
   batch_size = 1
   bo = SpectralBO(problem_type=f.problem_type, cat_vertices=f.config, cont_lb=f.lb, cont_ub=f.ub,
                   cat_dims=f.categorical_dims, cont_dims=f.continuous_dims, continuous_kern_type='smk', 
                   n_Cauchy=5, n_Gaussian=4, n_init=20, acq_func='ei', noise_variance=None, ard=True)
   

   Option 2b: Categorical problem

   f = QUBO()
   max_iters = 23
   batch_size = 1
   bo = SpectralBO(problem_type=f.problem_type, cat_vertices=f.config,  n_init=20, acq_func='ei', noise_variance=None, ard=True)
   

   Option 2c: Continuous problem

   f = Hartmann3()
   max_iters = 23
   batch_size = 1
   bo = SpectralBO(problem_type=f.problem_type, cont_lb=f.lb, cont_ub=f.ub,
                   continuous_kern_type='smk', n_Cauchy=9, n_Gaussian=0, n_init=20, acq_func='ucb',
                    noise_variance=None, ard=True)
   

3. Optimization loop

   for i in range(max_iters):
       x_next = bo.optim.suggest(batchsize=batch_size)
       y_next = f.compute(x_next)
       bo.optim.observe(x_next, y_next)
       Y = np.array(bo.optim.fX)
       if Y[:i].shape[0]:
           argmin = np.argmin(Y[:i * batch_size])
           print('Iter %d, Last X %s; \n fX:  %.4f. fX_best: %.4f'
                 % (i, x_next, float(Y[-1]), Y[:i * batch_size][argmin]))
   

Customize a New Optimization Problem

1. Go to ./test_func/base.py for the implementation of the base class. A new problem should be a derived class that properly implements all the required methods of the base class.

2. For different types of optimization problem, see examples in ./test_func/mixed.py, ./test_func/categorical.py, ./test_func/continuous.py, respectively

3. Edit the appropriate imports and other specifications and run from test.py as usual.

Citing SMKBO

If you use SMKBO, please cite the following paper:

@misc{zhang2025spectralmixturekernelsbayesian,
      title={Spectral Mixture Kernels for Bayesian Optimization}, 
      author={Yi Zhang and Cheng Hua},
      year={2025},
      eprint={2505.17393},
      archivePrefix={arXiv},
      primaryClass={cs.LG},
      url={https://arxiv.org/abs/2505.17393}, 
}

License

SMKBO is MIT licensed, as found in the LICENSE file.

Acknowledgements

This code repository uses materials from the following public repositories. The authors thank the respective repository maintainers

1. CASMOPOLITAN: Wan, X., Nguyen, V., Ha, H., Ru, B., Lu, C. & Osborne, M.A.. (2021). Think Global and Act Local: Bayesian Optimisation over High-Dimensional Categorical and Mixed Search Spaces. Proceedings of the 38th International Conference on Machine Learning (ICML). Code repo: https://github.com/xingchenwan/Casmopolitan.
2. BoTorch: M. Balandat, B. Karrer, D. R. Jiang, S. Daulton, B. Letham, A. G. Wilson, and E. Bakshy. (2020). BoTorch: A Framework for Efficient Monte-Carlo Bayesian Optimization. Advances in Neural Information Processing Systems 33 (NIPS 33). Code repo: https://github.com/pytorch/botorch.