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Title: Bayesian Prediction of Future Street Scenes using Synthetic Likelihoods

Paper content:
For autonomous agents to successfully operate in the real world, the ability to anticipate future scene states is a key competence.
In real-world scenarios, future states become increasingly uncertain and multi-modal, particularly on long time horizons.
Dropout based Bayesian inference provides a computationally tractable, theoretically well grounded approach to learn different hypotheses/models to deal with uncertain futures and make predictions that correspond well to observations -- are well calibrated.
However, it turns out that such approaches fall short to capture complex real-world scenes, even falling behind in accuracy when compared to the plain deterministic approaches.
This is because the used log-likelihood estimate discourages diversity.
In this work, we propose a novel Bayesian formulation for anticipating future scene states which leverages synthetic likelihoods that encourage the learning of diverse models to accurately capture the multi-modal nature of future scene states.
We show that our approach achieves accurate state-of-the-art predictions and calibrated probabilities through extensive experiments for scene anticipation on Cityscapes dataset.
Moreover, we show that our approach generalizes across diverse tasks such as digit generation and precipitation forecasting.
The ability to anticipate future scene states which involves mapping one scene state to likely future states under uncertainty is key for autonomous agents to successfully operate in the real world e.g., to anticipate the movements of pedestrians and vehicles for autonomous vehicles.
The future states of street scenes are inherently uncertain and the distribution of outcomes is often multi-modal.
This is especially true for important classes like pedestrians.
Recent works on anticipating street scenes BID13 BID9 BID23 do not systematically consider uncertainty.Bayesian inference provides a theoretically well founded approach to capture both model and observation uncertainty but with considerable computational overhead.
A recently proposed approach BID6 BID10 uses dropout to represent the posterior distribution of models and capture model uncertainty.
This approach has enabled Bayesian inference with deep neural networks without additional computational overhead.
Moreover, it allows the use of any existing deep neural network architecture with minor changes.However, when the underlying data distribution is multimodal and the model set under consideration do not have explicit latent state/variables (as most popular deep deep neural network architectures), the approach of BID6 ; BID10 is unable to recover the true model uncertainty (see FIG0 and BID19 ).
This is because this approach is known to conflate risk and uncertainty BID19 .
This limits the accuracy of the models over a plain deterministic (non-Bayesian) approach.
The main cause is the data log-likelihood maximization step during optimization -for every data point the average likelihood assigned by all models is maximized.
This forces every model to explain every data point well, pushing every model in the distribution to the mean.
We address this problem through an objective leveraging synthetic likelihoods BID26 BID21 which relaxes the constraint on every model to explain every data point, thus encouraging diversity in the learned models to deal with multi-modality.In this work:
1. We develop the first Bayesian approach to anticipate the multi-modal future of street scenes and demonstrate state-of-the-art accuracy on the diverse Cityscapes dataset without compromising on calibrated probabilities,
2. We propose a novel optimization scheme for dropout based Bayesian inference using synthetic likelihoods to encourage diversity and accurately capture model uncertainty,
3. Finally, we show that our approach is not limited to street scenes and generalizes across diverse tasks such as digit generation and precipitation forecasting.
We propose a novel approach for predicting real-world semantic segmentations into the future that casts a convolutional deep learning approach into a Bayesian formulation.
One of the key contributions is a novel optimization scheme that uses synthetic likelihoods to encourage diversity and deal with multi-modal futures.
Our proposed method shows state of the art performance in challenging street scenes.
More importantly, we show that the probabilistic output of our deep learning architecture captures uncertainty and multi-modality inherent to this task.
Furthermore, we show that the developed methodology goes beyond just street scene anticipation and creates new opportunities to enhance high performance deep learning architectures with principled formulations of Bayesian inference.

assistant: text: Dropout based Bayesian inference is extended to deal with multi-modality and is evaluated on scene anticipation tasks.