using System;

using System.Collections.Generic;

using System.Text;

using NumSharp;

using Tensorflow;

namespace TensorFlowNET.Examples

{

/// <summary>

/// Simple vanilla neural net solving the famous XOR problem

/// https://github.com/amygdala/tensorflow-workshop/blob/master/workshop_sections/getting_started/xor/README.md

/// </summary>

public class NeuralNetXor : Python, IExample

{

public int Priority => 10;

public bool Enabled { get; set; } = true;

public string Name => "NN XOR";

public int num_steps = 5000;

private NDArray data;

private (Operation, Tensor, RefVariable) make_graph(Tensor features,Tensor labels, int num_hidden = 8)

{

var stddev = 1 / Math.Sqrt(2);

var hidden_weights = tf.Variable(tf.truncated_normal(new int []{2, num_hidden}, stddev: (float) stddev ));

// Shape [4, num_hidden]

var hidden_activations = tf.nn.relu(tf.matmul(features, hidden_weights));

var output_weights = tf.Variable(tf.truncated_normal(

new[] {num_hidden, 1},

stddev: (float) (1 / Math.Sqrt(num_hidden))

));

// Shape [4, 1]

var logits = tf.matmul(hidden_activations, output_weights);

// Shape [4]

var predictions = tf.sigmoid(tf.squeeze(logits));

var loss = tf.reduce_mean(tf.square(predictions - tf.cast(labels, tf.float32)));

var gs = tf.Variable(0, trainable: false);

var train_op = tf.train.GradientDescentOptimizer(0.2f).minimize(loss, global_step: gs);

return (train_op, loss, gs);

}

public bool Run()

{

PrepareData();

var graph = tf.Graph().as_default();

var features = tf.placeholder(tf.float32, new TensorShape(4, 2));

var labels = tf.placeholder(tf.int32, new TensorShape(4));

var (train_op, loss, gs) = make_graph(features, labels);

var init = tf.global_variables_initializer();

float loss_value = 0;

// Start tf session

with(tf.Session(graph), sess =>

{

sess.run(init);

var step = 0;

var y_ = np.array(new int[] { 1, 0, 0, 1 }, dtype: np.int32);

while (step < num_steps)

{

// original python:

//_, step, loss_value = sess.run(

// [train_op, gs, loss],

// feed_dict={features: xy, labels: y_}

// )

loss_value = sess.run(loss, new FeedItem(features, data), new FeedItem(labels, y_));

step++;

if (step%1000==0)

Console.WriteLine($"Step {step} loss: {loss_value}");

}

Console.WriteLine($"Final loss: {loss_value}");

});

return loss_value < 0.0627;

}

public void PrepareData()

{

data = new float[,]

{

{1, 0 },

{1, 1 },

{0, 0 },

{0, 1 }

};

}

}

}