fann_train_epoch

(PECL fann >= 1.0.0)

fann_train_epoch — 使用一组训练数据训练一个周期。

说明

fann_train_epoch(resource $ann, resource $data): float

使用保存在 data 中训练数据训练一个周期。一个训练周期表示所有的训练数据正好使用了一次。

这个函数将会返回在其实际计算之前或当中被计算的 MSE 错误。但是因为计算需要再次走一遍整个训练集，所有训练周期之后的不是真正的 MSE。在训练中使用这个值是绰绰有余的。

该函数使用的是被 fann_set_training_algorithm() 函数选中的训练算法。

参数

ann: 神经网络资源。
data: 神经网络训练数据资源。

返回值

成功，则返回 MSE, 错误则返回 false .

参见

fann_train_on_data() - 在整个数据集上训练一段时间。
fann_test_data() - 使用训练数据来测试并且计算出 MSE
fann_get_MSE() - 从网络中读取均方误差。
fann_set_training_algorithm() - 设置训练算法。

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geekgirljoy at gmail dot com ¶

6 years ago

This code demonstrates training XOR using fann_train_epoch and will let you watch the training process by observing a psudo MSE (mean squared error).

Other training functions: fann_train_on_data, fann_train_on_file, fann_train.

fann_train_epoch is useful when you want to observe the ANN while it is training and perhaps save snapshots or compare competing networks during training. 

fann_train_epoch is different from fann_train in that it takes a data resource (training file) whereas fann_train takes an array of inputs and a separate array of outputs so use fann_train_epoch for observing training on data files (callback training resources) and use fann_train when observing manually specified data. 

Example code: 

<?php
$num_input = 2;
$num_output = 1;
$num_layers = 3; 
$num_neurons_hidden = 3; 
$desired_error = 0.0001;
$max_epochs = 500000;
$current_epoch = 0;
$epochs_between_saves = 100; // Minimum number of epochs between saves
$epochs_since_last_save = 0;
$filename = dirname(__FILE__) . "/xor.data";

// Initialize psudo mse (mean squared error) to a number greater than the desired_error
// this is what the network is trying to minimize.
$psudo_mse_result = $desired_error * 10000; // 1
$best_mse = $psudo_mse_result; // keep the last best seen MSE network score here

// Initialize ANN
$ann = fann_create_standard($num_layers, $num_input, $num_neurons_hidden, $num_output);

if ($ann) {
  echo 'Training ANN... ' . PHP_EOL; 
  
  // Configure the ANN
  fann_set_training_algorithm ($ann , FANN_TRAIN_BATCH);
  fann_set_activation_function_hidden($ann, FANN_SIGMOID_SYMMETRIC);
  fann_set_activation_function_output($ann, FANN_SIGMOID_SYMMETRIC);
  
  // Read training data
  $train_data = fann_read_train_from_file($filename);
  
  
  // Check if psudo_mse_result is greater than our desired_error 
  // if so keep training so long as we are also under max_epochs
  while(($psudo_mse_result > $desired_error) && ($current_epoch <= $max_epochs)){
    $current_epoch++;
    $epochs_since_last_save++;  
  
    // See: http://php.net/manual/en/function.fann-train-epoch.php
    // Train one epoch with the training data stored in data. 
    //
    // One epoch is where all of the training data is considered 
    // exactly once.
    //
    // This function returns the MSE error as it is calculated 
    // either before or during the actual training. This is not the 
    // actual MSE after the training epoch, but since calculating this 
    // will require to go through the entire training set once more. 
    // It is more than adequate to use this value during training.
    $psudo_mse_result = fann_train_epoch ($ann , $train_data );
    echo 'Epoch ' . $current_epoch . ' : ' . $psudo_mse_result . PHP_EOL; // report
    
    
    // If we haven't saved the ANN in a while...
    // and the current network is better then the previous best network
    // as defined by the current MSE being less than the last best MSE
    // Save it!
    if(($epochs_since_last_save >= $epochs_between_saves) && ($psudo_mse_result < $best_mse)){
      
      $best_mse = $psudo_mse_result; // we have a new best_mse
      
      // Save a Snapshot of the ANN
      fann_save($ann, dirname(__FILE__) . "/xor.net");
      echo 'Saved ANN.' . PHP_EOL; // report the save
      $epochs_since_last_save = 0; // reset the count
    }
  
  } // While we're training

  echo 'Training Complete! Saving Final Network.'  . PHP_EOL;
  
  // Save the final network
  fann_save($ann, dirname(__FILE__) . "/xor.net");  
  fann_destroy($ann); // free memory
}
echo 'All Done!' . PHP_EOL;
?>