comparison toolboxes/FullBNT-1.0.7/bnt/CPDs/@mlp_CPD/mlp_CPD.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function CPD = mlp_CPD(bnet, self, nhidden, w1, b1, w2, b2, clamped, max_iter, verbose, wthresh,  llthresh)
+% MLP_CPD Make a CPD from a Multi Layer Perceptron (i.e., feedforward neural network)
+%
+% We use a different MLP for each discrete parent combination (if there are any discrete parents).
+% We currently assume this node (the child) is discrete.
+%
+% CPD = mlp_CPD(bnet, self, nhidden)
+% will create a CPD with random parameters, where self is the number of this node and nhidden the number of the hidden nodes.
+% The params are drawn from N(0, s*I), where s = 1/sqrt(n+1), n = length(X).
+%
+% CPD = mlp_CPD(bnet, self, nhidden, w1, b1, w2, b2) allows you to specify the params, where
+%  w1 = first-layer weight matrix
+%  b1 = first-layer bias vector
+%  w2 = second-layer weight matrix
+%  b2 = second-layer bias vector
+% These are assumed to be the same for each discrete parent combination.
+% If any of these are [], random values will be created.
+%
+% CPD = mlp_CPD(bnet, self, nhidden, w1, b1, w2, b2, clamped) allows you to prevent the params from being
+% updated during learning (if clamped = 1). Default: clamped = 0.
+%
+% CPD = mlp_CPD(bnet, self, nhidden, w1, b1, w2, b2, clamped, max_iter, verbose, wthresh,  llthresh)
+% alllows you to specify params that control the M step:
+%  max_iter - the maximum number of steps to take (default: 10)
+%  verbose - controls whether to print (default: 0 means silent).
+%  wthresh - a measure of the precision required for the value of
+%     the weights W at the solution. Default: 1e-2.
+%  llthresh - a measure of the precision required of the objective
+%     function (log-likelihood) at the solution.  Both this and the previous condition must
+%     be satisfied for termination. Default: 1e-2.
+%
+% For learning, we use a weighted version of scaled conjugated gradient in the M step.
+
+if nargin==0
+  % This occurs if we are trying to load an object from a file.
+  CPD = init_fields;
+  CPD = class(CPD, 'mlp_CPD', discrete_CPD(0,[]));
+  return;
+elseif isa(bnet, 'mlp_CPD')
+  % This might occur if we are copying an object.
+  CPD = bnet;
+  return;
+end
+CPD = init_fields;
+
+assert(myismember(self, bnet.dnodes));
+ns = bnet.node_sizes;
+
+ps = parents(bnet.dag, self);
+dnodes = mysetdiff(1:length(bnet.dag), bnet.cnodes);
+dps = myintersect(ps, dnodes);
+cps = myintersect(ps, bnet.cnodes);
+dpsz = prod(ns(dps));
+cpsz = sum(ns(cps));
+self_size = ns(self);
+
+% discrete/cts parent index - which ones of my parents are discrete/cts?
+CPD.dpndx = find_equiv_posns(dps, ps); 
+CPD.cpndx = find_equiv_posns(cps, ps);
+
+CPD.mlp = cell(1,dpsz);
+for i=1:dpsz
+    CPD.mlp{i} = mlp(cpsz, nhidden, self_size, 'softmax');
+    if nargin >=4 & ~isempty(w1)
+        CPD.mlp{i}.w1 = w1;
+    end
+    if nargin >=5 & ~isempty(b1)
+        CPD.mlp{i}.b1 = b1; 
+    end
+    if nargin >=6 & ~isempty(w2)
+        CPD.mlp{i}.w2 = w2; 
+    end
+    if nargin >=7 & ~isempty(b2)
+        CPD.mlp{i}.b2 = b2; 
+    end
+    W1app(:,:,i)=CPD.mlp{i}.w1;
+    W2app(:,:,i)=CPD.mlp{i}.w2;
+    b1app(i,:)=CPD.mlp{i}.b1;
+    b2app(i,:)=CPD.mlp{i}.b2;
+end
+if nargin < 8, clamped = 0; end
+if nargin < 9, max_iter = 10; end
+if nargin < 10, verbose = 0; end
+if nargin < 11, wthresh = 1e-2; end
+if nargin < 12, llthresh = 1e-2; end
+
+CPD.self = self;
+CPD.max_iter = max_iter;
+CPD.verbose = verbose;
+CPD.wthresh = wthresh;
+CPD.llthresh = llthresh;
+
+% sufficient statistics 
+% Since MLP is not in the exponential family, we must store all the raw data.
+%
+CPD.W1=W1app;                     % Extract all the parameters of the node for handling discrete obs parents
+CPD.W2=W2app;                     %
+nparaW=[size(W1app) size(W2app)]; %
+CPD.b1=b1app;                     %
+CPD.b2=b2app;                     %
+nparab=[size(b1app) size(b2app)]; %
+
+CPD.sizes=bnet.node_sizes(:);   % used in CPD_to_table to pump up the node sizes
+
+CPD.parent_vals = [];        % X(l,:) = value of cts parents in l'th example
+
+CPD.eso_weights=[];          % weights used by the SCG algorithm 
+
+CPD.self_vals = [];          % Y(l,:) = value of self in l'th example
+
+% For BIC
+CPD.nsamples = 0;   
+CPD.nparams=prod(nparaW)+prod(nparab);
+CPD = class(CPD, 'mlp_CPD', discrete_CPD(clamped, ns([ps self])));
+
+%%%%%%%%%%%
+
+function CPD = init_fields()
+% This ensures we define the fields in the same order 
+% no matter whether we load an object from a file,
+% or create it from scratch. (Matlab requires this.)
+
+CPD.mlp = {};
+CPD.self = [];
+CPD.max_iter = [];
+CPD.verbose = [];
+CPD.wthresh = [];
+CPD.llthresh = [];
+CPD.approx_hess = [];
+CPD.W1 = [];
+CPD.W2 = [];
+CPD.b1 = [];
+CPD.b2 = [];
+CPD.sizes = [];
+CPD.parent_vals = [];
+CPD.eso_weights=[];
+CPD.self_vals = [];
+CPD.nsamples = [];
+CPD.nparams = [];