View Index by Level
RANDOM PAGE

SITE SEARCH

LOG
IN

SIGN UP

HELP

Neural Networks


This is the AQA version closing after June 2019. Visit the the version for Eduqas instead.

To gain access to revision questions, please sign up and log in.

A2

Neural Network Architecture

NeuralNet.gif

To Train a Network

This is one simple method.

  • Make some random changes to the strengths of the links between the processors.
  • Test the new network.
  • If it performs better, keep the changes.
  • If it is the same or worse, discard the changes and try again.
  • Repeat these steps until the network performance is good enough.

A method is needed to work out a performance score for measuring the quality.

OCR ANN Simulator

Comparing Conventional and Neural Network Computation

 

Conventional Computer

Neural Network

Inputs

  • A few inputs like a keyboard, mouse or bar code scanner.
  • Many inputs, possibly thousands.
  • For example an image recognition system would have inputs for each pixel.

Processor

  • A single processor which deals with all the data.
  • Some computers have two or four processors but rarely more.
  • Many processors, possibly thousands.
  • Each processor is much simpler than a conventional computer processor.
  • Each processor deals with a small part of the data.
  • The processors work in parallel.

Programming

  • Must be programmed by a programmer.
  • Must be trained.
  • Neural networks learn instead of being programmed.
  • Learning takes place by links being made stronger or weaker.

Memory

  • Data stored centrally (ROM, RAM, hard disk)
  • Data stored as weightings in the network.

Applications

Solves well defined problems like

  • payroll or
  • bank account management.
  • Can do precise maths.
  • Good for solving problems with small numbers of inputs and where the algorithm (set of rules) for solving the problem is well understood.

Better at predictive problems such as ...

  • Weather forecasting
  • Image recognition. Solves problems like image recognition (spot the criminal or terrorist in the shopping mall).
  • Good for solving problems with vast amounts of input data where the rules for reaching the answer are fuzzy or not well defined.

 

 

 

reviseOmatic V3     Contacts, ©, Cookies, Data Protection and Disclaimers Hosted at linode.com, London