LSTM Auxiliary Loss for Long-Sequence Dependency

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Solution Overview

Problem

Neural networks, particularly recurrent neural networks, face challenges in capturing and remembering long-term dependencies in sequences, leading to inefficiencies in training due to vanishing or exploding gradients and the high cost of lengthy backpropagation through time (BPTT).

Innovation Solution

Incorporating an unsupervised auxiliary loss function into the LSTM neural network, which encourages the network to remember past events and predict future events by using anchor points for truncated backpropagation, reducing the need for lengthy BPTT and improving optimization and generalization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If gradient descent and backpropagation through time (BPTT) with recurrent networks is used to understand long-term dependencies, then the network can capture relationships between distant events, but the training becomes computationally expensive and suffers from vanishing or exploding gradients

Engineering Contradiction:
Improveability to capture long-term dependenciesVSAvoidcomputational complexity of training
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the long sequence processing into multiple shorter BPTT steps by introducing intermediate target variables at different time steps. Instead of computing gradients over the entire long sequence in one step, the training process divides it into manageable segments, each handling a specific time range. This segmentation reduces computational complexity and prevents gradient vanishing/exploding while maintaining the ability to capture long-term dependencies across the full sequence.

Inventive Principle:
Principle #1Segmentation

2Manufacturing precision

If lengthy backpropagation through time (BPTT) is performed during training to obtain good results, then the network achieves good performance on long sequences, but the training time and computational cost become critical bottlenecks

Engineering Contradiction:
Improvetraining accuracyVSAvoidtraining time
Core Design Contradiction:
Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-computing and storing intermediate target variables at various time steps during the forward pass. These pre-computed targets are then used during the backward pass to guide gradient computation at specific intervals, avoiding the need to propagate gradients through the entire long sequence. This preliminary preparation of intermediate targets significantly reduces training time while maintaining training accuracy.

Inventive Principle:
Principle #10Preliminary action

3Duration of action of stationary object

If the network processes very long sequences using standard BPTT, then it can theoretically capture all dependencies, but vanishing or exploding gradients become critical bottlenecks

Engineering Contradiction:
Improvesequence lengthVSAvoidgradient stability
Core Design Contradiction:
Duration of action of stationary objectVSReliability

Solution Approach 1:

The patent introduces intermediate target variables as mediators between the input and output at different time steps. These intermediate targets act as anchors that stabilize gradient flow by providing reference points for gradient computation. Instead of gradients traveling directly through the entire long sequence (which causes vanishing/exploding problems), the intermediate targets break the gradient path into stable segments, maintaining gradient stability throughout very long sequences.

Inventive Principle:
Principle #24Intermediary (Mediator)

Data Source

PatentUS11501168B2Learning longer-term dependencies in neural network using auxiliary losses
Publication Date: 2022.11.15 GOOGLE LLC
  • US11501168B2 patent drawing
  • US11501168B2 patent drawing
  • US11501168B2 patent drawing

AI summary

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for structuring and training a recurrent neural network. This describes a technique that improves the ability to capture long term dependencies in recurrent neural networks by adding an unsupervised auxiliary loss at one or more anchor points to the original objective. This auxiliary loss forces the network to either reconstruct previous events or predict next events in a sequence, making truncated backpropagation feasible for long sequences and also improving full backpropagation through time.