From a0344b429c17f1d5d9cea5b5ffaa77c36fc17850 Mon Sep 17 00:00:00 2001
From: Gnome Ann <>
Date: Tue, 1 Mar 2022 15:40:44 -0500
Subject: [PATCH] Upload torch_lazy_loader.py

---
 torch_lazy_loader.py | 95 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 torch_lazy_loader.py

diff --git a/torch_lazy_loader.py b/torch_lazy_loader.py
new file mode 100644
index 00000000..c5211050
--- /dev/null
+++ b/torch_lazy_loader.py
@@ -0,0 +1,95 @@
+import contextlib
+import pickle
+import torch
+from typing import Any, Callable, Dict, Optional, Tuple, Type
+
+
+class LazyTensor:
+    def __init__(self, storage_type: Type[torch._StorageBase], key: str, location: str, nelements: int, storage_offset: Optional[int] = None, shape: Optional[Tuple[int, ...]] = None, stride: Optional[Tuple[int, ...]] = None, requires_grad=False, backward_hooks: Any = None):
+        self.storage_type = storage_type
+        self.key = key
+        self.location = location
+        self.nelements = nelements
+        self.storage_offset = storage_offset
+        self.shape = shape
+        self.stride = stride
+        self.requires_grad = requires_grad
+        self.backward_hooks = backward_hooks
+
+    def __view(self, f: Callable):
+        return f"{type(self).__name__}(storage_type={f(self.storage_type)}, key={f(self.key)}, location={f(self.location)}, nelements={f(self.nelements)}, storage_offset={f(self.storage_offset)}, shape={f(self.shape)}, stride={f(self.stride)}, requires_grad={f(self.requires_grad)}, backward_hooks={f(self.backward_hooks)})"
+
+    def __repr__(self):
+        return self.__view(repr)
+
+    def materialize(self, checkpoint: torch._C.PyTorchFileReader, map_location=None) -> torch.Tensor:
+        storage_dtype = self.storage_type(0).dtype
+        storage = checkpoint.get_storage_from_record(f"data/{self.key}", self.nelements, storage_dtype).storage()
+        storage = torch.serialization._get_restore_location(map_location)(storage, self.location)
+        tensor = torch.tensor([], dtype=storage.dtype, device=storage.device)
+        tensor.set_(storage, self.storage_offset, self.shape, self.stride)
+        tensor.requires_grad = self.requires_grad
+        tensor._backward_hooks = self.backward_hooks
+        return tensor
+
+
+class _LazyUnpickler(pickle.Unpickler):
+    lazy_loaded_storages: Dict[str, LazyTensor]
+
+    def __init__(self, *args, **kwargs):
+        self.lazy_loaded_storages = {}
+        return super().__init__(*args, **kwargs)
+
+    def forced_persistent_load(self, saved_id):
+        assert isinstance(saved_id, tuple)
+        typename = saved_id[0]
+        assert typename == "storage", f"Unknown typename for persistent_load, expected 'storage' but got '{typename}'"
+
+        storage_type, key, location, nelements = saved_id[1:]
+
+        if key not in self.lazy_loaded_storages:
+            self.lazy_loaded_storages[key] = LazyTensor(storage_type, key, location, nelements)
+        
+        return self.lazy_loaded_storages[key]
+
+    def load(self, *args, **kwargs):
+        self.persistent_load = self.forced_persistent_load
+        retval = super().load(*args, **kwargs)
+        self.lazy_loaded_storages = {}
+        return retval
+
+
+def _rebuild_tensor(lazy_storage: LazyTensor, storage_offset, shape, stride):
+    lazy_storage.storage_offset = storage_offset
+    lazy_storage.shape = shape
+    lazy_storage.stride = stride
+    return lazy_storage
+
+
+@contextlib.contextmanager
+def use_lazy_torch_load(enable=True, callback: Optional[Callable] = None):
+    if not enable:
+        yield False
+        return
+
+    old_unpickler = pickle.Unpickler
+    pickle.Unpickler = _LazyUnpickler
+
+    old_rebuild_tensor = torch._utils._rebuild_tensor
+    torch._utils._rebuild_tensor = _rebuild_tensor
+
+    old_torch_load = torch.load
+
+    def torch_load(f, map_location=None, pickle_module=pickle, **pickle_load_args):
+        retval = old_torch_load(f=f, map_location=map_location, pickle_module=pickle_module, **pickle_load_args)
+        if callback is not None:
+            callback(retval, f=f, map_location=map_location, pickle_module=pickle_module, **pickle_load_args)
+        return retval
+
+    torch.load = torch_load
+
+    yield True
+
+    pickle.Unpickler = old_unpickler
+    torch._utils._rebuild_tensor = old_rebuild_tensor
+    torch.load = old_torch_load