VAE Sampling via Isometric Latent Space Transformation

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Solution Overview

Problem

Existing sampling methods using machine learning models with latent spaces, such as VAEs, face inefficiencies in generating independent samples due to high proposal costs, strong model constraints, and approximate likelihood evaluations, leading to low acceptance probabilities and deteriorated sample generation efficiency.

Innovation Solution

A sampling method utilizing a VAE with a potential isometric property, where the latent space is transformed into an isometric space using non-linear mapping, allowing for efficient generation of independent samples with high acceptance probabilities by calculating acceptance probabilities based on transformation rules and metric tensors, eliminating the need for approximate likelihood evaluations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a VAE with latent space is used for sampling, then the model can learn complex data distributions, but the proposal cost becomes high and acceptance probability decreases

Engineering Contradiction:
Improvesampling accuracyVSAvoidsample generation efficiency
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent segments the sampling process into two distinct spaces: the latent space for efficient proposal generation using VAE, and the data space for accurate acceptance evaluation using metric tensors. This segmentation allows each component to optimize for its specific function, resolving the contradiction between proposal efficiency and acceptance accuracy.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary transformation rule that maps between the latent space and data space. This intermediary enables efficient sampling in the latent space while maintaining accurate probability evaluation in the data space, thus resolving the efficiency-accuracy tradeoff.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Productivity

If approximate likelihood evaluation is used to reduce computational complexity, then processing speed improves, but sampling accuracy deteriorates

Engineering Contradiction:
Improvecomputational speedVSAvoidlikelihood evaluation accuracy
Core Design Contradiction:
ProductivityVSMeasurement precision

Solution Approach 1:

The patent substitutes the traditional mechanical computation of likelihood ratios with a geometric approach using metric tensors and transformation rules. This substitution eliminates the need for approximate likelihood evaluations while maintaining computational efficiency, as the acceptance probability can be directly calculated from the transformation Jacobian and metric tensors.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If strong constraints are imposed on the machine learning model to ensure proper sampling, then model reliability improves, but device complexity increases

Engineering Contradiction:
Improvesampling correctnessVSAvoidmodel constraint complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the parameter representation from direct likelihood values to geometric quantities (metric tensors and transformation Jacobians). This parameter change simplifies the model constraints, as the acceptance probability can be directly computed from these geometric parameters without requiring complex likelihood ratio calculations.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS20240119118A1Computer-readable recording medium storing sampling program, sampling method, and information processing apparatus
Publication Date: 2024.04.11 FUJITSU LTD
  • US20240119118A1 patent drawing
  • US20240119118A1 patent drawing
  • US20240119118A1 patent drawing

AI summary

A non-transitory computer-readable recording medium stores a program for causing a computer to execute a sampling process including: converting first data in a latent space into second data in a data space by using a machine learning model that has the latent space transformable into an isometric space with same probability distribution as the data space according to a predetermined transformation rule; determining whether or not to accept the second data as a transition state in a Markov chain Monte Carlo method from an accepted first sample in the data space with an acceptance probability based on the transformation rule; and outputting the second data as a second sample of the transition state from the first sample when the second data is determined to be accepted.