code: import os
  
  import numpy as np
  import torch
  from tensorboardX import SummaryWriter
  
  import distributed
  from models.reporter_ext import ReportMgr, Statistics
  from others.logging import logger
  from others.utils import test_rouge, rouge_results_to_str
  
  
  def _tally_parameters(model):
      n_params = sum([p.nelement() for p in model.parameters()])
      return n_params
  
  
  def build_trainer(args, device_id, model, optim):
      """
      Simplify `Trainer` creation based on user `opt`s*
      Args:
          opt (:obj:`Namespace`): user options (usually from argument parsing)
          model (:obj:`onmt.models.NMTModel`): the model to train
          fields (dict): dict of fields
          optim (:obj:`onmt.utils.Optimizer`): optimizer used during training
          data_type (str): string describing the type of data
              e.g. "text", "img", "audio"
          model_saver(:obj:`onmt.models.ModelSaverBase`): the utility object
              used to save the model
      """
  
      grad_accum_count = args.accum_count
      n_gpu = args.world_size
  
      if device_id >= 0:
          gpu_rank = int(args.gpu_ranks[device_id])
      else:
          gpu_rank = 0
          n_gpu = 0
  
      print('gpu_rank %d' % gpu_rank)
  
      tensorboard_log_dir = args.model_path
  
      writer = SummaryWriter(tensorboard_log_dir, comment="Unmt")
  
      report_manager = ReportMgr(args.report_every, start_time=-1, tensorboard_writer=writer)
  
      trainer = Trainer(args, model, optim, grad_accum_count, n_gpu, gpu_rank, report_manager)
  
      # print(tr)
      if (model):
          n_params = _tally_parameters(model)
          logger.info('* number of parameters: %d' % n_params)
  
      return trainer
  
  
  class Trainer(object):
      """
      Class that controls the training process.
  
      Args:
              model(:py:class:`onmt.models.model.NMTModel`): translation model
                  to train
              train_loss(:obj:`onmt.utils.loss.LossComputeBase`):
                 training loss computation
              valid_loss(:obj:`onmt.utils.loss.LossComputeBase`):
                 training loss computation
              optim(:obj:`onmt.utils.optimizers.Optimizer`):
                 the optimizer responsible for update
              trunc_size(int): length of truncated back propagation through time
              shard_size(int): compute loss in shards of this size for efficiency
              data_type(string): type of the source input: [text|img|audio]
              norm_method(string): normalization methods: [sents|tokens]
              grad_accum_count(int): accumulate gradients this many times.
              report_manager(:obj:`onmt.utils.ReportMgrBase`):
                  the object that creates reports, or None
              model_saver(:obj:`onmt.models.ModelSaverBase`): the saver is
                  used to save a checkpoint.
                  Thus nothing will be saved if this parameter is None
      """
  
      def __init__(self, args, model, optim,
                   grad_accum_count=1, n_gpu=1, gpu_rank=1,
                   report_manager=None):
          # Basic attributes.
          self.args = args
          self.save_checkpoint_steps = args.save_checkpoint_steps
          self.model = model
          self.optim = optim
          self.grad_accum_count = grad_accum_count
          self.n_gpu = n_gpu
          self.gpu_rank = gpu_rank
          self.report_manager = report_manager
  
          self.loss = torch.nn.BCELoss(reduction='none')
          assert grad_accum_count > 0
          # Set model in training mode.
          if (model):
              self.model.train()
  
      def train(self, train_iter_fct, train_steps, valid_iter_fct=None, valid_steps=-1):
          """
          The main training loops.
          by iterating over training data (i.e. `train_iter_fct`)
          and running validation (i.e. iterating over `valid_iter_fct`
  
          Args:
              train_iter_fct(function): a function that returns the train
                  iterator. e.g. something like
                  train_iter_fct = lambda: generator(*args, **kwargs)
              valid_iter_fct(function): same as train_iter_fct, for valid data
              train_steps(int):
              valid_steps(int):
              save_checkpoint_steps(int):
  
          Return:
              None
          """
          logger.info('Start training...')
  
          # step =  self.optim._step + 1
          step = self.optim._step + 1
          true_batchs = []
          accum = 0
          normalization = 0
          train_iter = train_iter_fct()
  
          total_stats = Statistics()
          report_stats = Statistics()
          self._start_report_manager(start_time=total_stats.start_time)
  
          while step <= train_steps:
  
              reduce_counter = 0
              for i, batch in enumerate(train_iter):
                  if self.n_gpu == 0 or (i % self.n_gpu == self.gpu_rank):
  
                      true_batchs.append(batch)
                      normalization += batch.batch_size
                      accum += 1
                      if accum == self.grad_accum_count:
                          reduce_counter += 1
                          if self.n_gpu > 1:
                              normalization = sum(distributed
                                                  .all_gather_list
                                                  (normalization))
  
                          self._gradient_accumulation(
                              true_batchs, normalization, total_stats,
                              report_stats)
  
                          report_stats = self._maybe_report_training(
                              step, train_steps,
                              self.optim.learning_rate,
                              report_stats)
  
                          true_batchs = []
                          accum = 0
                          normalization = 0
                          if (step % self.save_checkpoint_steps == 0 and self.gpu_rank == 0):
                              self._save(step)
  
                          step += 1
                          if step > train_steps:
                              break
              train_iter = train_iter_fct()
  
          return total_stats
  
      def validate(self, valid_iter, step=0):
          """ Validate model.
              valid_iter: validate data iterator
          Returns:
              :obj:`nmt.Statistics`: validation loss statistics
          """
          # Set model in validating mode.
          self.model.eval()
          stats = Statistics()
  
          with torch.no_grad():
              for batch in valid_iter:
                  src = batch.src
                  labels = batch.src_sent_labels
                  segs = batch.segs
                  clss = batch.clss
                  mask = batch.mask_src
                  mask_cls = batch.mask_cls
  
                  sent_scores, mask = self.model(src, segs, clss, mask, mask_cls)
  
                  loss = self.loss(sent_scores, labels.float())
                  loss = (loss * mask.float()).sum()
                  batch_stats = Statistics(float(loss.cpu().data.numpy()), len(labels))
                  stats.update(batch_stats)
              self._report_step(0, step, valid_stats=stats)
              return stats
  
      def test(self, test_iter, step, cal_lead=False, cal_oracle=False):
          """ Validate model.
              valid_iter: validate data iterator
          Returns:
              :obj:`nmt.Statistics`: validation loss statistics
          """
  
          # Set model in validating mode.
          def _get_ngrams(n, text):
              ngram_set = set()
              text_length = len(text)
              max_index_ngram_start = text_length - n
              for i in range(max_index_ngram_start + 1):
                  ngram_set.add(tuple(text[i:i + n]))
              return ngram_set
  
          def _block_tri(c, p):
              tri_c = _get_ngrams(3, c.split())
              for s in p:
                  tri_s = _get_ngrams(3, s.split())
                  if len(tri_c.intersection(tri_s)) > 0:
                      return True
              return False
  
          if (not cal_lead and not cal_oracle):
              self.model.eval()
          stats = Statistics()
  
          can_path = '%s_step%d.candidate' % (self.args.result_path, step)
          gold_path = '%s_step%d.gold' % (self.args.result_path, step)
          ##
          src_path = '%s_step%d.src' % (self.args.result_path, step)
          f = open(src_path, 'w')
          ##
          sent_no = 0
          with open(can_path, 'w') as save_pred:
              with open(gold_path, 'w') as save_gold:
                  with torch.no_grad():
                      for batch in test_iter:
                          src = batch.src
                          labels = batch.src_sent_labels
                          segs = batch.segs
                          clss = batch.clss
                          mask = batch.mask_src
                          mask_cls = batch.mask_cls
  
                          gold = []
                          pred = []
                          src_fix = []
  
                          if (cal_lead):
                              selected_ids = [list(range(batch.clss.size(1)))] * batch.batch_size
                          elif (cal_oracle):
                              selected_ids = [[j for j in range(batch.clss.size(1)) if labels[i][j] == 1] for i in
                                              range(batch.batch_size)]
                          else:
                              sent_scores, mask = self.model(src, segs, clss, mask, mask_cls)
                              if labels.float().size()[1] != 0:
                                  loss = self.loss(sent_scores, labels.float())
                              else:
                                  continue
                              loss = (loss * mask.float()).sum()
                              batch_stats = Statistics(float(loss.cpu().data.numpy()), len(labels))
                              stats.update(batch_stats)
  
                              sent_scores = sent_scores + mask.float()
                              sent_scores = sent_scores.cpu().data.numpy()
                              selected_ids = np.argsort(-sent_scores, 1)
  
                              if len(selected_ids[0]) < 7:
                                  continue
                          # selected_ids = np.sort(selected_ids,1)
                          for i, idx in enumerate(selected_ids):
                              _pred = []
                              if (len(batch.src_str[i]) == 0):
                                  continue
                              for j in selected_ids[i][:len(batch.src_str[i])]:
                                  if (j >= len(batch.src_str[i])):
                                      continue
                                  candidate = batch.src_str[i][j].strip()
                                  if (self.args.block_trigram):
                                      if (not _block_tri(candidate, _pred)):
                                          _pred.append(candidate)
                                  else:
                                      _pred.append(candidate)
  
                                  if ((not cal_oracle) and (not self.args.recall_eval) and len(_pred) == 3):
                                      break
  
                              _pred = '<q>'.join(_pred)
                              if (self.args.recall_eval):
                                  _pred = ' '.join(_pred.split()[:len(batch.tgt_str[i].split())])
  
                              pred.append(_pred)
                              gold.append(batch.tgt_str[i])
                              src_fix.append(batch.src_str[i])
                              sent_no += 1
                              # print(sent_no)
  
                          # print('gold', gold)
                          # print(gold_path)
  
                          for i in range(len(gold)):
                              save_gold.write(str(sent_no) + "_" + str(i) + ': ' + gold[i].strip() + '\n')
                          for i in range(len(pred)):
                              save_pred.write(str(sent_no) + "_" + str(i) + ': ' + pred[i].strip() + '\n')
                          for i in range(len(pred)):
                              f.write(str(sent_no) + "_" + str(i) + ': ' + '###'.join(src_fix[i]).strip()+'\n')
          f.close()
          if (step != -1 and self.args.report_rouge):
              rouges = test_rouge(self.args.temp_dir, can_path, gold_path)
              logger.info('Rouges at step %d \n%s' % (step, rouge_results_to_str(rouges)))
          self._report_step(0, step, valid_stats=stats)
  
          return stats
  
      def _gradient_accumulation(self, true_batchs, normalization, total_stats,
                                 report_stats):
          if self.grad_accum_count > 1:
              self.model.zero_grad()
  
          for batch in true_batchs:
              if self.grad_accum_count == 1:
                  self.model.zero_grad()
  
              src = batch.src
              labels = batch.src_sent_labels
              segs = batch.segs
              clss = batch.clss
              mask = batch.mask_src
              mask_cls = batch.mask_cls
  
              sent_scores, mask = self.model(src, segs, clss, mask, mask_cls)
  
              loss = self.loss(sent_scores, labels.float())
              loss = (loss * mask.float()).sum()
              (loss / loss.numel()).backward()
              # loss.div(float(normalization)).backward()
  
              batch_stats = Statistics(float(loss.cpu().data.numpy()), normalization)
  
              total_stats.update(batch_stats)
              report_stats.update(batch_stats)
  
              # 4. Update the parameters and statistics.
              if self.grad_accum_count == 1:
                  # Multi GPU gradient gather
                  if self.n_gpu > 1:
                      grads = [p.grad.data for p in self.model.parameters()
                               if p.requires_grad
                               and p.grad is not None]
                      distributed.all_reduce_and_rescale_tensors(
                          grads, float(1))
                  self.optim.step()
  
          # in case of multi step gradient accumulation,
          # update only after accum batches
          if self.grad_accum_count > 1:
              if self.n_gpu > 1:
                  grads = [p.grad.data for p in self.model.parameters()
                           if p.requires_grad
                           and p.grad is not None]
                  distributed.all_reduce_and_rescale_tensors(
                      grads, float(1))
              self.optim.step()
  
      def _save(self, step):
          real_model = self.model
          # real_generator = (self.generator.module
          #                   if isinstance(self.generator, torch.nn.DataParallel)
          #                   else self.generator)
  
          model_state_dict = real_model.state_dict()
          # generator_state_dict = real_generator.state_dict()
          checkpoint = {
              'model': model_state_dict,
              # 'generator': generator_state_dict,
              'opt': self.args,
              'optims': self.optim,
          }
          checkpoint_path = os.path.join(self.args.model_path, 'model_step_%d.pt' % step)
          logger.info("Saving checkpoint %s" % checkpoint_path)
          # checkpoint_path = '%s_step_%d.pt' % (FLAGS.model_path, step)
          if (not os.path.exists(checkpoint_path)):
              torch.save(checkpoint, checkpoint_path)
              return checkpoint, checkpoint_path
  
      def _start_report_manager(self, start_time=None):
          """
          Simple function to start report manager (if any)
          """
          if self.report_manager is not None:
              if start_time is None:
                  self.report_manager.start()
              else:
                  self.report_manager.start_time = start_time
  
      def _maybe_gather_stats(self, stat):
          """
          Gather statistics in multi-processes cases
  
          Args:
              stat(:obj:onmt.utils.Statistics): a Statistics object to gather
                  or None (it returns None in this case)
  
          Returns:
              stat: the updated (or unchanged) stat object
          """
          if stat is not None and self.n_gpu > 1:
              return Statistics.all_gather_stats(stat)
          return stat
  
      def _maybe_report_training(self, step, num_steps, learning_rate,
                                 report_stats):
          """
          Simple function to report training stats (if report_manager is set)
          see `onmt.utils.ReportManagerBase.report_training` for doc
          """
          if self.report_manager is not None:
              return self.report_manager.report_training(
                  step, num_steps, learning_rate, report_stats,
                  multigpu=self.n_gpu > 1)
  
      def _report_step(self, learning_rate, step, train_stats=None,
                       valid_stats=None):
          """
          Simple function to report stats (if report_manager is set)
          see `onmt.utils.ReportManagerBase.report_step` for doc
          """
          if self.report_manager is not None:
              return self.report_manager.report_step(
                  learning_rate, step, train_stats=train_stats,
                  valid_stats=valid_stats)
  
      def _maybe_save(self, step):
          """
          Save the model if a model saver is set
          """
          if self.model_saver is not None:
              self.model_saver.maybe_save(step)
  
apis: torch.nn.BCELoss torch.save torch.no_grad numpy.argsort