Construct multivariate normal distribution from GP, facilitate sampling

RBF Kernel all parameters are in log-scale

Linear Kernel

Rational quardratic kernel

Constant mean

Gauss Process

Iso Periodic kernel

Neural Kernel Network modify https://github.com/FluxML/Flux.jl/tree/master/src/layers/basic.jl Chain

Primitive layer, constituted by basic kernels

general composite kernel

Product layer

special composite kernels

simple neural network mean (single layer, linear)

dispatch parameters (Array) to a ML model, facilitate use of Optim.jl

Linear layer: weigths & bias should be positive