neat_phenotype.hpp

Go to the documentation of this file.

 
#pragma once
 
#include <algorithm>
#include <cmath>
#include <functional>
#include <map>
#include <stdexcept>
#include <vector>
 
#include "pulsatrix/neat_genome.hpp"
 
namespace pulsatrix {
 
inline std::vector<double> EvaluateNEATPhenotype(const NEATGenome& genome, const std::vector<double>& inputs) {
    std::vector<int> input_ids;
    std::vector<int> output_ids;
    int bias_id = -1;
    for (const auto& n : genome.nodes()) {
        switch (n.type) {
            case NodeGene::Type::Input:
                input_ids.push_back(n.id);
                break;
            case NodeGene::Type::Bias:
                bias_id = n.id;
                break;
            case NodeGene::Type::Output:
                output_ids.push_back(n.id);
                break;
            case NodeGene::Type::Hidden:
                break;
        }
    }
    std::sort(input_ids.begin(), input_ids.end());
    std::sort(output_ids.begin(), output_ids.end());
 
    if (inputs.size() != input_ids.size()) {
        throw std::invalid_argument("EvaluateNEATPhenotype: inputs.size() must match the genome's Input node count");
    }
 
    std::map<int, double> fixed_values;
    for (size_t i = 0; i < input_ids.size(); ++i) {
        fixed_values[input_ids[i]] = inputs[i];
    }
    if (bias_id != -1) {
        fixed_values[bias_id] = 1.0;
    }
 
    std::map<int, double> cache;
    std::function<double(int)> evaluate = [&](int node_id) -> double {
        auto fixed_it = fixed_values.find(node_id);
        if (fixed_it != fixed_values.end()) {
            return fixed_it->second;
        }
        auto cached_it = cache.find(node_id);
        if (cached_it != cache.end()) {
            return cached_it->second;
        }
        double sum = 0.0;
        for (const auto& c : genome.connections()) {
            if (c.enabled && c.out_node == node_id) {
                sum += c.weight * evaluate(c.in_node);
            }
        }
        double activated = 1.0 / (1.0 + std::exp(-4.9 * sum));
        cache[node_id] = activated;
        return activated;
    };
 
    std::vector<double> outputs;
    outputs.reserve(output_ids.size());
    for (int id : output_ids) {
        outputs.push_back(evaluate(id));
    }
    return outputs;
}
 
}  // namespace pulsatrix