Variational Autoencoder Temporal Pooling for Posterior Collapse

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Solution Overview

Problem

Sequence variational autoencoders (VAEs) are prone to posterior collapse during training, where the model relies excessively on local processing channels, ignoring global context due to noise and bottlenecks, leading to suboptimal information processing and degeneration into regular language models.

Innovation Solution

Implementing a pooling mechanism across the temporal dimension of all hidden states to generate feature vectors, rather than relying solely on the last hidden state, which helps maintain the variability of input sequences and prevents posterior collapse by dispersing the initial input representation across noisy channels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If pooling operations are applied over temporal dimension of hidden states, then global context capture and long-range dependencies are enhanced, but computational complexity and processing time increase

Engineering Contradiction:
Improveglobal context informationVSAvoidprocessing time
Core Design Contradiction:
Loss of informationVSLoss of time

Solution Approach 1:

The patent segments the temporal dimension of hidden states into multiple pooled features (max pooling, mean pooling, absolute pooling) rather than processing the entire sequence as a single unit. This segmentation allows efficient extraction of global context information at different levels, reducing the computational burden compared to processing all temporal information in full detail.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces pooling operations as intermediary mechanisms between the RNN hidden states and the final sequence representation. These pooling operations act as mediators that aggregate temporal information efficiently, capturing global context without requiring direct processing of all individual time steps, thus reducing processing time while maintaining information quality.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If pooling operations are applied over temporal dimension of hidden states, then the model prevents posterior collapse and maintains variability, but device complexity and computational resources increase

Engineering Contradiction:
Improvetraining stabilityVSAvoidmodel architecture complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges multiple pooling operations (max pooling, mean pooling, absolute pooling) to collectively prevent posterior collapse. By combining these different pooling strategies, the model maintains variability in the latent space more effectively than any single pooling operation alone, improving training stability while distributing the computational load across multiple simpler operations rather than one complex mechanism.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the parameters of the pooling operations (different types of pooling, different aggregation methods) to optimize the balance between preventing posterior collapse and managing computational complexity. By adjusting these parameters, the model can maintain training stability with controlled increases in device complexity.

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If pooling operations aggregate hidden states, then feature representation quality improves, but the temporal resolution and sequence detail are reduced

Engineering Contradiction:
Improvefeature representation accuracyVSAvoidtemporal sequence length
Core Design Contradiction:
Measurement precisionVSLength of stationary object

Solution Approach 1:

The patent applies pooling operations along the temporal dimension, effectively changing the dimensionality of the hidden states by aggregating across time steps. This allows the model to achieve high feature representation accuracy in the pooled dimensions while accepting reduced temporal resolution, as the pooling operates specifically along the time axis rather than compressing all dimensions equally.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS11914955B2System and method for machine learning architecture with variational autoencoder pooling
Publication Date: 2024.02.27 ROYAL BANK OF CANADA
  • US11914955B2 patent drawing
  • US11914955B2 patent drawing
  • US11914955B2 patent drawing

AI summary

A computer implemented method is described for conducting text sequence machine learning, the method comprising: receiving an input sequence x=[x1, x2, . . . , xn], to produce a feature vector for a series of hidden states hx=[h1, h2, . . . , hn], wherein the feature vector for the series of hidden states hx is generated by performing pooling over a temporal dimension of all hidden states output by the encoder machine learning data architecture; and extracting from the series of hidden states hx, a mean and a variance parameter, and to encapsulate the mean and the variance parameter as an approximate posterior data structure.