Roberto Calandra PRO
Professor at TU Dresden. Interested in AI and Robotics.
Roberto Calandra
Facebook AI Research
CS188 - UC Berkeley - 10 April 2020
Optimized parameters
Objective function
Parameters to optimize
Single minimum
(e.g., convex functions)
Multiple minimum
(a.k.a., global optimization)
First-order
(we can measure gradients)
Zero-order
(no gradients available)
Noise-less
(repeating the evaluation yield the same result)
Stochastic
(repeating the evaluation yield different results)
Nice and easy to solve
(e.g., with gradient descent)
Cheap Evaluation
(virtually infinite number of evaluations allowed)
Difficult to optimize!
Expensive Evaluation
(limited to tens or hundreds of evaluations)
Oil drilling
Design and manufacturing
Drug design
Robotics
Hyperparameters optimization
Vibrant community dedicated to automated machine learning (AutoML)
With dozens of parameters, complex correlations, and expensive evaluations
these methods become impractical
e.g.,
We can create a surrogate model
Gradient descent
[credit: Marc Deisenroth]
Large variety of models used throughout the literature:
By far the most commonly used (currently)
Surrogate model (a.k.a. response surface) need to accurately approximate (and generalize) the underlying function based on the available data
Additional reading:
Rasmussen, C. E. & Williams, C. K. I.
Gaussian Processes for Machine Learning
The MIT Press, 2006
Mean of a GP = Kernel ridge regression
Square exponential
parameters of the GP
(often referred to as hyperparameters)
Multiple ways to optimize the hyperparameters
Additional reading:
Rasmussen, C. E. & Williams, C. K. I.
Gaussian Processes for Machine Learning
The MIT Press, 2006
Pro:
Cons:
Numberless extensions in the literature:
Optimized parameters
Objective function
Parameters to optimize
Context
Pareto Front
[Knowles, J. ParEGO: A hybrid algorithm with on-line landscape approximation for expensive multiobjective optimization problems IEEE Transactions on Evolutionary Computation, 2006, 10, 50-66]
Bio-inspired Bipedal Robot "Fox":
[Calandra, R.; Seyfarth, A.; Peters, J. & Deisenroth, M. P. Bayesian Optimization for Learning Gaits under Uncertainty Annals of Mathematics and Artificial Intelligence (AMAI), 2015, 76, 5-23]
[Calandra, R.; Seyfarth, A.; Peters, J. & Deisenroth, M. P. Bayesian Optimization for Learning Gaits under Uncertainty Annals of Mathematics and Artificial Intelligence (AMAI), 2015, 76, 5-23]
[Calandra, R.; Seyfarth, A.; Peters, J. & Deisenroth, M. P. Bayesian Optimization for Learning Gaits under Uncertainty Annals of Mathematics and Artificial Intelligence (AMAI), 2015, 76, 5-23]
Not Symmetrical (about 5° difference). Why?
Because it is walking in a circle!
[Calandra, R.; Seyfarth, A.; Peters, J. & Deisenroth, M. P. Bayesian Optimization for Learning Gaits under Uncertainty Annals of Mathematics and Artificial Intelligence (AMAI), 2015, 76, 5-23]
Simulated hexapod:
[Yang, B.; Wang, G.; Calandra, R.; Contreras, D.; Levine, S. & Pister, K. Learning Flexible and Reusable Locomotion Primitives for a Microrobot IEEE Robotics and Automation Letters (RA-L), 2018, 3, 1904-1911]
[Yang, B.; Wang, G.; Calandra, R.; Contreras, D.; Levine, S. & Pister, K. Learning Flexible and Reusable Locomotion Primitives for a Microrobot IEEE Robotics and Automation Letters (RA-L), 2018, 3, 1904-1911]
[Yang, B.; Wang, G.; Calandra, R.; Contreras, D.; Levine, S. & Pister, K. Learning Flexible and Reusable Locomotion Primitives for a Microrobot IEEE Robotics and Automation Letters (RA-L), 2018, 3, 1904-1911]
[Yang, B.; Wang, G.; Calandra, R.; Contreras, D.; Levine, S. & Pister, K. Learning Flexible and Reusable Locomotion Primitives for a Microrobot IEEE Robotics and Automation Letters (RA-L), 2018, 3, 1904-1911]
[Yang, B.; Wang, G.; Calandra, R.; Contreras, D.; Levine, S. & Pister, K. Learning Flexible and Reusable Locomotion Primitives for a Microrobot IEEE Robotics and Automation Letters (RA-L), 2018, 3, 1904-1911]
[Yang, B.; Wang, G.; Calandra, R.; Contreras, D.; Levine, S. & Pister, K. Learning Flexible and Reusable Locomotion Primitives for a Microrobot IEEE Robotics and Automation Letters (RA-L), 2018, 3, 1904-1911]
[Yang, B.; Wang, G.; Calandra, R.; Contreras, D.; Levine, S. & Pister, K. Learning Flexible and Reusable Locomotion Primitives for a Microrobot IEEE Robotics and Automation Letters (RA-L), 2018, 3, 1904-1911]
[Yang, B.; Wang, G.; Calandra, R.; Contreras, D.; Levine, S. & Pister, K. Learning Flexible and Reusable Locomotion Primitives for a Microrobot IEEE Robotics and Automation Letters (RA-L), 2018, 3, 1904-1911]
Please give Feedback at: https://tinyurl.com/cs188introbo
Shahriari, B.; Swersky, K.; Wang, Z.; Adams, R. P. & de Freitas, N.
Taking the human out of the loop: A review of Bayesian optimization
Proceedings of the IEEE, IEEE, 2016, 104, 148-175
Rasmussen, C. E. & Williams, C. K. I.
Gaussian Processes for Machine Learning
The MIT Press, 2006
Knowles, J.
ParEGO: A hybrid algorithm with on-line landscape approximation for expensive multiobjective optimization problems
IEEE Transactions on Evolutionary Computation, 2006, 10, 50-66
Hutter, F.; Hoos, H. H. & Leyton-Brown, K.
Sequential model-based optimization for general algorithm configuration
Learning and Intelligent Optimization (LION), Springer, 2011, 507-523
Snoek, J.; Larochelle, H. & Adams, R. P.
Practical Bayesian Optimization of Machine Learning Algorithms
arXiv preprint arXiv:1206.2944, 2012
By Roberto Calandra
[cs188 - UC Berkeley - 10 April 2020]
Professor at TU Dresden. Interested in AI and Robotics.