Source code for torch_xla.utils.serialization

from __future__ import division
from __future__ import print_function

import os
import shutil

import torch
import torch_xla
import torch_xla.utils.utils as xu
import torch_xla.core.xla_model as xm


class TensorReference(object):

  def __init__(self, tid):
    self.tid = tid


def _get_tensors_folder(path):
  return path + '.tensors'


def _get_tensor_file(path, tid):
  return os.path.join(path, 'tensor_{}.pt'.format(tid))


def _rewrite_data(path, data, save_tensors):

  def convert_fn(tensors):
    torch_xla._XLAC._xla_sync_multi(
        tensors, devices=[], wait=True, sync_xla_data=True)
    rewritten_tensors = []
    for i, t in enumerate(tensors):
      if save_tensors:
        torch.save(t.cpu(), _get_tensor_file(path, i))
      rewritten_tensors.append(TensorReference(i))
    return rewritten_tensors

  def select_fn(v):
    return type(v) == torch.Tensor and xm.is_xla_tensor(v)

  if os.path.isdir(path):
    shutil.rmtree(path)
  os.mkdir(path)
  return xm.ToXlaTensorArena(convert_fn, select_fn).transform(data)


def save(data, path, master_only=True, global_master=False):
  """Saves the input data into a file.

  The saved data is transferred to PyTorch CPU device before being saved, so a
  following `torch.load()` will load CPU data.
  Care must be taken when working with views. Instead of saving views it's
  recommended that you recreate them after the tensors have been loaded and
  moved to their destination device(s).

  Args:
    data: The input data to be saved. Any nested combination of Python objects
      (list, tuples, sets, dicts, ...).
    path: The destination file for the data saving operation. If `master_only`
      is ``False`` the path must point to different destinations as otherwise
      all the writes from the same host will override each other.
    master_only (bool, optional): Whether only the master device should save the
      data. If False, the `path` argument should be a different path for each of
      the ordinals taking part to the replication, otherwise all the replicas on
      the same host will be writing to the same location.
      Default: True
    global_master (bool, optional): When ``master_only`` is ``True`` this flag
      controls whether every host's master (if ``global_master`` is ``False``)
      saves the content, or only the global master (ordinal 0).
      Default: False
  """
  should_write_data = not master_only or xm.is_master_ordinal(
      local=not global_master)

  ref_data = _rewrite_data(_get_tensors_folder(path), data, should_write_data)
  if should_write_data:
    torch.save(ref_data, path)
  xm.rendezvous('torch_xla.utils.serialization.save')


def load(path):
  """Loads data previously saved with the `save()` API.

  Args:
    path (str): The path passed to the `save()` API.
  Returns:
    The loaded data.
  """
  ref_data = torch.load(path)
  tensor_folder = _get_tensors_folder(path)

  def convert_fn(tensors):
    rewritten_tensors = []
    for t in tensors:
      rewritten_tensors.append(
          torch.load(_get_tensor_file(tensor_folder, t.tid)))
    return rewritten_tensors

  def select_fn(v):
    return type(v) == TensorReference

  return xm.ToXlaTensorArena(convert_fn, select_fn).transform(ref_data)