On Jul 9, 2013, at 4:14 AM, Bojan Janisch wrote:



> what do I have to do, to build a complete GPTree and use it for evaluation?

> 

> Background is that I have now successfully created my first rules from a GPTree. 

> But I want to know if the results would be better if I use a rule that I manually 

> wrote, as a GPIndividuum in my population. 





If you just want to build a GPTree manually, you just need to allocate various GPNodes and hang them together.  I'll presume you don't care about making a new GPIndividual, just constructing a GPTree and evaluating it.



To allocate GPNodes you might need your function set.  Let's say that your GPTree was intended to fit into tree slot s of your GPIndividual (in most cases you just have one tree per individual, so s=0).  You might do:



final EvolutionState state =  ...

final Subpopulation subpop = ... 

final GPInitializer init = (GPInitializer)(state.initializer);

final GPSpecies gps = (GPSpecies)(subpop.species);

final GPIndividual indproto = ((GPIndividual)(gps.i_prototype));

final GPTree gptproto = indproto.trees[0];

final GPTreeConstraints gptc = gptproto.constraints(init);

final GPFunctionSet gpfs = gptc.functionset;



Okay, now you have your function set.  See GPFunctionSet to extract specific GPNodes.  For example, you can make a node whose name is "+" like this:



GPNode plus = (GPNode)(gpfs.nodesByName.get("+").clone());  // ALWAYS clone



A GPNode has three critical variables that you will need to set.



    public GPNodeParent parent;

    public GPNode children[];

    public byte argposition;



Parent points to the parent GPNode of the node, or to a GPTree if the node is the root.  You probably don't need to attach to a tree if you're just evaluating the tree, just let that value be null.



children[] is an array of the children nodes to the node.  children[] can be null, or can be zero length, if the node is a leaf.



argposition is the index in the parent's children array in which this node is found.  It says "I'm child number 4 of my parent", for example.



Let's say we're trying to create the tree:   (+ (cos x) x)



I'd do this:



GPNode plus =  (GPNode)(gpfs.nodesByName.get("+").clone());

GPNode cos =  (GPNode)(gpfs.nodesByName.get("cos").clone());

GPNode x_one =  (GPNode)(gpfs.nodesByName.get("+").clone());

GPNode x_two =  (GPNode)(gpfs.nodesByName.get("+").clone());



plus.parent = null;  // no GPTree :-(

plus.argposition = 0;

plus.children[0] = cos;

plus.children[1] = x_one;



cos.parent = plus;

cos.argposition = 0;

cos.children[0] = x_two;



x_one.parent = plus;

x_one.argposition = 1;

x_one.children = null;  // it's probably already null anyway



x_two.parent = cos;

x_two.argposition = 0;

x_two.children = null;  // it's probably null already



Now you're ready to evaluate the node.



GPProblem prob = ...

GPData gpd = ...

int threadnum = ...

GPIndividual ind = null;  // our GPNodes don't need the individual to evaluate

plus.eval(state, threadnum, gpd, new ADFStack(), ind, prob);



If you need the GPTree or the GPIndividual constructed as well, then there's a bit more to that.



Sean