wolffd@0: net = mlp(nin, nhidden, nout, func) wolffd@0: net = mlp(nin, nhidden, nout, func, prior) wolffd@0: net = mlp(nin, nhidden, nout, func, prior, beta) wolffd@0:wolffd@0: wolffd@0: wolffd@0:
net = mlp(nin, nhidden, nout, func) takes the number of inputs,
wolffd@0: hidden units and output units for a 2-layer feed-forward network,
wolffd@0: together with a string func which specifies the output unit
wolffd@0: activation function, and returns a data structure net. The
wolffd@0: weights are drawn from a zero mean, unit variance isotropic Gaussian,
wolffd@0: with varianced scaled by the fan-in of the hidden or output units as
wolffd@0: appropriate. This makes use of the Matlab function
wolffd@0: randn and so the seed for the random weight initialization can be
wolffd@0: set using randn('state', s) where s is the seed value.
wolffd@0: The hidden units use the tanh activation function.
wolffd@0:
wolffd@0: The fields in net are
wolffd@0:
wolffd@0: wolffd@0: type = 'mlp' wolffd@0: nin = number of inputs wolffd@0: nhidden = number of hidden units wolffd@0: nout = number of outputs wolffd@0: nwts = total number of weights and biases wolffd@0: actfn = string describing the output unit activation function: wolffd@0: 'linear' wolffd@0: 'logistic wolffd@0: 'softmax' wolffd@0: w1 = first-layer weight matrix wolffd@0: b1 = first-layer bias vector wolffd@0: w2 = second-layer weight matrix wolffd@0: b2 = second-layer bias vector wolffd@0:wolffd@0: wolffd@0: Here
w1 has dimensions nin times nhidden, b1 has
wolffd@0: dimensions 1 times nhidden, w2 has
wolffd@0: dimensions nhidden times nout, and b2 has
wolffd@0: dimensions 1 times nout.
wolffd@0:
wolffd@0: net = mlp(nin, nhidden, nout, func, prior), in which prior is
wolffd@0: a scalar, allows the field net.alpha in the data structure
wolffd@0: net to be set, corresponding to a zero-mean isotropic Gaussian
wolffd@0: prior with inverse variance with value prior. Alternatively,
wolffd@0: prior can consist of a data structure with fields alpha
wolffd@0: and index, allowing individual Gaussian priors to be set over
wolffd@0: groups of weights in the network. Here alpha is a column vector
wolffd@0: in which each element corresponds to a separate group of weights,
wolffd@0: which need not be mutually exclusive. The membership of the groups is
wolffd@0: defined by the matrix indx in which the columns correspond to
wolffd@0: the elements of alpha. Each column has one element for each
wolffd@0: weight in the matrix, in the order defined by the function
wolffd@0: mlppak, and each element is 1 or 0 according to whether the
wolffd@0: weight is a member of the corresponding group or not. A utility
wolffd@0: function mlpprior is provided to help in setting up the
wolffd@0: prior data structure.
wolffd@0:
wolffd@0:
net = mlp(nin, nhidden, nout, func, prior, beta) also sets the
wolffd@0: additional field net.beta in the data structure net, where
wolffd@0: beta corresponds to the inverse noise variance.
wolffd@0:
wolffd@0:
mlpprior, mlppak, mlpunpak, mlpfwd, mlperr, mlpbkp, mlpgradCopyright (c) Ian T Nabney (1996-9) wolffd@0: wolffd@0: wolffd@0: wolffd@0: