Software Simulation of a Self-organizing Learning Array System Janusz Starzyk & Zhen Zhu School of EECS Ohio University
Theme SOLAR = Self-organizing Learning Array Introduction to SOLAR Software simulation Performance of SOLAR
Introduction to SOLAR SOLAR : Artificial neural networks (ANN) Self-organizing structure Re-configurable hardware
Introduction to SOLAR Basic frame of SOLAR: A fixed lattice of processing units (neurons) Self-organization: Interconnections among the units refined during learning
Software Simulation - SOLAR Simulation tasks: Pre-processing of input data to SOLAR Behavior of a single neuron Network structure Classification Assembly of various networks
Software Simulation - SOLAR Inputs & outputs of SOLAR:
Software Simulation - SOLAR Real world input data features X: Incomplete set – data missing Symbolic – unacceptable to neural computation Unbalance weighted – needs to be equalized Pre-processing: Calculate default substitutes for missing data Set continuous values to all symbols Rescaling
Software Simulation - SOLAR Missing data problem: Find defaults for missing items in each individual inputs to minimize Mahalanobis distance. Separate known items X k, and missing items X m X=[X k, X m ]. Compute covariance matrix and its inversed matrix. Partition matrix. Compute default X m
Software Simulation - SOLAR Inputs & outputs of a single SOLAR neuron:
Software Simulation - SOLAR Behavior of a single SOLAR neuron: Output behaves a selected functions of input. Unary input operations: O=Y(I 1 ) or O=Y(I 2 ). Binary input operations: O=Y(I 1, I 2 ). All the operations are redesigned arithmetic operations. -Linear/ non-linear -Input/output range is set as
Software Simulation - SOLAR Unary input operations: Identical function : Y=IDENT(x)= Half function: Y=HALF(x)= Logarithm function: Y=NLOG2(x)= Exponential function:Y= NEXP2(x)= Binary input operations: Addition function: Y=NADD(x1,x2)= Subtraction function: Y=NSUB(x1,x2)=
Software Simulation - SOLAR Example: Y=NLOG2(x)=
Software Simulation - SOLAR HOW does a neuron learn from training data and process on testing data? Each neuron chooses an operation and a threshold. The whole input space will be cut into 2 parts (subspaces). Ex:
Software Simulation - SOLAR Neuron learning Neurons learn from each other and generates more complicated cuttings.
Software Simulation - SOLAR Neuron learning In order to effectively separate different classes, a neuron may choose from different configure options. processing unit Input clock function and 1 threshold are selected
Software Simulation - SOLAR Classification On each individual testing input data point, some of or all the neurons are active in classification. Neurons are activated with input clocks. Each neuron saves classification probabilities based on subspace division. Ex: subspace 1subspace 2 class 1 60% 10% class 2 10% 80% class 3 30% 10%
Software Simulation - SOLAR Classification On each testing input data point, some neurons have sufficient knowledge from learning and become eligible. They vote on the classification of this point.
Software Simulation - SOLAR Classification Several independent SOLAR networks form an ensemble to vote on the same problem.
Performance Evaluation - SOLAR An Australian credit card data set [1] is used to evaluate SOLAR performance. 14 input features, 690 individuals, 2 classes This data set is a typical classification problem and has been used to test other classic classification algorithms [2].
Performance Evaluation - SOLAR Divide the data set into 10 groups randomly. Run the simulation 10 times. Each time use 1 group for testing the the remaining for training. Average the resultant classification rate. Experimented on single SOLAR and SOLAR ensemble.
Performance Evaluation - SOLAR MethodMiss RateMethodMiss Rate CAL50.131Naivebay0.151 DIPOL CASTLE0.148 Logdisc0.141ALLOC SMART0.158CART0.145 C NewID0.181 IndCART0.152CN Bprop0.154LVQ0.197 Discrim0.141Kohenen - RBF0.145Quadisc0.207 Baytree0.171Default0.440 ITule0.137 AC20.181SOLAR0.183 k-NN0.181ensemble0.135
Performance Evaluation - SOLAR Conclusion: Although SOLAR was not designed with any particular purposes, it works well with several classification problems. SOLAR behaviors are observed in this simulation.
References [1] Y. Liu, X. Yao and T. Higuchi, “Evolutionary Ensembles with Negative Correlation Learning”, IEEE Trans. on Evolutionary Computation, Vol. 4, No. 4, Nov [2] D. Michie, D. J. Spiegelhalter, and C. C. Taylor, “Machine Learning, Neural and Statistical Classification” London, U. K. Ellis Horwood Ltd. 1994