Questions on Notes Flashcards
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Give details on the two brain initiatives
Brain Initiative:
- broad looked into different ways of studying the brain
- $300mil
- finished
Human Brain Project:
- map enough neurons to simulate part of the brain
- $1bil
- complained for being too narrow
- ongoing
Name the types of output functions
Linear
Step
Sigmoid
Describe the 4 learning rules
Plain Hebb: if both the pre-synaptic and post-synaptic neurons fired together the weights should increase.
Post-synaptic: if the post-synaptic neuron fires the weight should increase
Pre-synaptic: if the pre-synaptic neuron fires the weight should increase
Covariance: the increase in the weight is proportional to the difference between the two neurons
Describe the types of neural networks
Perceptron:
- single layer
- linearly separable
Multilayer Perceptron:
- not linearly separable as long as a non-linear output function is used
- hidden layers
Recurrent Neural network
- creates memory
- used when there is a time series
Describe the data sets needed and why
Training set
- this is used so the NN learns the weights
Validation set
- used to prevent overfitting
Give examples of applications for NN
NetTalk
- learnt to read aloud from written text
AlphaGo
- taught itself the game of Go
What are the limitations of NN
- can be overfitted to the data
- the results can be fooled
- cyberattack of dataset
- Bais from datasets used
- Blackbox means it is not easily possible to understand the process the NN took
Detail what is required to define a cellular system
Cell space
- 1D 2D 3D hexagonal
Neighbourhood
- which cells influence each other
Transition rule
- how a cell reacts to its neighbours
Boundary conditions
- Assigned, periodic, adiabatic, reflection
Initial conditions
What is the universality of CAs
Theoretically, they can compute anything as they are capable of universal computation. The game of life can do this
Give examples for the uses of CAs
- solve mazes
- model physics
What are the limitations of CAs
- no way to predict the outcome without running it
- difficult to design the rules for a specific behaviour
Detail the 4 pillars of evolution
Population: a group of several individuals
Diversity: individuals have different characteristics
Heredity: characteristics are transmitted over generations
Selection: individuals produce more offspring then the environment can support
What are the genotype and phenotype
Genotype
- the genetic material of the organism
- selection does not directly operate
Phenotype
- manifestation of the organism
- selection operates on the phenotype
Describe the differences between natural and artificial evolution
- Fitness is a measure of the individual’s ability to solve the problem
- Selection is according to the performance criteria
- It is expected that the performance will improve over the generations
Describe the types of genetic representation
Discrete
- eg binary string mapping to several phenotypes
Sequence
- sequence of values (travelling salesman)
Real-value
- sequence of real values that represent parameters eg wing profile
Tree-based
- describes a tree with branching points and terminals
Describe the types of fitness functions
Explicit: eg lift-drag
Implicit: maximum flight time
Subjective: most aesthetic
Why is selection pressure important
too strong and there is a rapid loss in diversity which could lead to a suboptimal solution.
too slow and the solution will not converge in a reasonable timeframe
List the types of selection
Proportional
Rank based
Tournament
Describe proportional based selection
- the probability of an individual producing offspring is proportional to its fitness with regards to the group’s fitness.
- if fitness is uniform selection is weak
- if there is an outperforming individual it can result in a lack of diversity
Describe rank based selection
- individuals are ranked based on their performance
- offspring is then produced proportional to their rank or from the selected best few
Describe tournament based selection
- a random group of set size is picked and competes against one another
- the champion is then selected to produced offspring
Describe the types of inheritance
One point: a proportion of the genotype at a point is switched
uniform: every other value in the genotype is switched
Arithmetic: an average of the genotype is produced
How can performance be monitored
Fitness landscape
- observe the average fitness of the population and the maximum fitness
Diversity
- when diversity decreases the potential for further evolution decreases
Only really useful when the problem is stationary