Skip to content

Fix Loader restoration before None items #1552

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
aswanth-07 wants to merge 3 commits into
base: main
Choose a base branch
from
Open

Fix Loader restoration before None items #1552

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
be7f7d4
Fix Loader restoration before None items
aswanth-07 Aug 23, 2026
b88467a
Clear Loader cached state on reset
aswanth-07 Sep 3, 2026
cb6f8b4
Merge branch 'main' into fix/loader-none-lookahead
aswanth-07 Sep 15, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
23 changes: 23 additions & 0 deletions test/nodes/test_loader.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -53,3 +53,26 @@ def test_loader_equal_state_dict_on_save_load_map(self) -> None:
length = 10
node = MapStyleWrapper(DummyMapDataset(length), sampler=range(length))
self._test_loader_correct_state_dict_at_midpoint(node, length)

def test_loader_restores_before_none_item(self) -> None:
loader = Loader(IterableWrapper([0, None, 2]))
iterator = iter(loader)
self.assertEqual(next(iterator), 0)
state_dict = loader.state_dict()

restored = Loader(IterableWrapper([0, None, 2]))
restored.load_state_dict(state_dict)

self.assertEqual(list(restored), [None, 2])

def test_loader_reset_clears_cached_state_dict(self) -> None:
checkpoint_source = Loader(IterableWrapper([0, 1, 2]))
self.assertEqual(next(iter(checkpoint_source)), 0)
state_dict = checkpoint_source.state_dict()

loader = Loader(IterableWrapper([0, 1, 2]))
self.assertTrue(iter(loader).has_next())
loader.load_state_dict(state_dict)
iter(loader)

self.assertEqual(loader.state_dict(), state_dict)
11 changes: 8 additions & 3 deletions torchdata/nodes/loader.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,7 @@ def __init__(
self.loader = loader
self.root = loader.root
self._cached_item = None
self._has_cached_item = False
self._cached_state_dict: Optional[Dict[str, Any]] = None
self._num_yielded = 0

Expand All @@ -110,22 +111,26 @@ def reset(self, initial_state: Optional[Dict[str, Any]] = None):
self.root.reset(None)
self._num_yielded = 0
self._cached_item = None
self._has_cached_item = False
self._cached_state_dict = None

def has_next(self) -> bool:
if self._cached_item is None:
if not self._has_cached_item:
try:
# Cache the current state dict
self._cached_state_dict = self.state_dict()
# Load and save the next item
self._cached_item = next(self)
self._has_cached_item = True
except StopIteration:
pass
return self._cached_item is not None
return self._has_cached_item

def next(self):
if self._cached_item is not None:
if self._has_cached_item:
item = self._cached_item
self._cached_item = None
self._has_cached_item = False
self._cached_state_dict = None
else:
item = next(self.root)
Expand Down