in timm/data/loader.py [0:0]
def fast_collate(batch):
""" A fast collation function optimized for uint8 images (np array or torch) and int64 targets (labels)"""
assert isinstance(batch[0], tuple)
batch_size = len(batch)
if isinstance(batch[0][0], tuple):
# This branch 'deinterleaves' and flattens tuples of input tensors into one tensor ordered by position
# such that all tuple of position n will end up in a torch.split(tensor, batch_size) in nth position
is_np = isinstance(batch[0][0], np.ndarray)
inner_tuple_size = len(batch[0][0])
flattened_batch_size = batch_size * inner_tuple_size
targets = torch.zeros(flattened_batch_size, dtype=torch.int64)
tensor = torch.zeros((flattened_batch_size, *batch[0][0][0].shape), dtype=torch.uint8)
for i in range(batch_size):
assert len(batch[i][0]) == inner_tuple_size # all input tensor tuples must be same length
for j in range(inner_tuple_size):
targets[i + j * batch_size] = batch[i][1]
if is_np:
tensor[i + j * batch_size] += torch.from_numpy(batch[i][0][j])
else:
tensor[i + j * batch_size] += batch[i][0][j]
return tensor, targets
elif isinstance(batch[0][0], np.ndarray):
targets = torch.tensor([b[1] for b in batch], dtype=torch.int64)
assert len(targets) == batch_size
tensor = torch.zeros((batch_size, *batch[0][0].shape), dtype=torch.uint8)
for i in range(batch_size):
tensor[i] += torch.from_numpy(batch[i][0])
return tensor, targets
elif isinstance(batch[0][0], torch.Tensor):
targets = torch.tensor([b[1] for b in batch], dtype=torch.int64)
assert len(targets) == batch_size
tensor = torch.zeros((batch_size, *batch[0][0].shape), dtype=torch.uint8)
for i in range(batch_size):
tensor[i].copy_(batch[i][0])
return tensor, targets
else:
assert False