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import torch as t
def corn_loss(logits, y_train, num_classes):
"""Computes the CORN loss described in our forthcoming
'Deep Neural Networks for Rank Consistent Ordinal
Regression based on Conditional Probabilities'
manuscript.
Parameters
----------
logits : torch.tensor, shape=(num_examples, num_classes-1)
Outputs of the CORN layer.
y_train : torch.tensor, shape=(num_examples)
Torch tensor containing the class labels.
num_classes : int
Number of unique class labels (class labels should start at 0).
Returns
----------
loss : torch.tensor
A torch.tensor containing a single loss value.
Examples
----------
>>> import torch
>>> from coral_pytorch.losses import corn_loss
>>> # Consider 8 training examples
>>> _ = torch.manual_seed(123)
>>> X_train = torch.rand(8, 99)
>>> y_train = torch.tensor([0, 1, 2, 2, 2, 3, 4, 4])
>>> NUM_CLASSES = 5
>>> #
>>> #
>>> # def __init__(self):
>>> corn_net = torch.nn.Linear(99, NUM_CLASSES-1)
>>> #
>>> #
>>> # def forward(self, X_train):
>>> logits = corn_net(X_train)
>>> logits.shape
torch.Size([8, 4])
>>> corn_loss(logits, y_train, NUM_CLASSES)
tensor(0.7127, grad_fn=<DivBackward0>)
https://github.com/Raschka-research-group/coral-pytorch/blob/c6ab93afd555a6eac708c95ae1feafa15f91c5aa/coral_pytorch/losses.py
"""
sets = []
for i in range(num_classes - 1):
label_mask = y_train > i - 1
label_tensor = (y_train[label_mask] > i).to(t.int64)
sets.append((label_mask, label_tensor))
num_examples = 0
losses = 0.0
for task_index, s in enumerate(sets):
train_examples = s[0]
train_labels = s[1]
if len(train_labels) < 1:
continue
num_examples += len(train_labels)
pred = logits[train_examples, task_index]
loss = -t.sum(
t.nn.functional.logsigmoid(pred) * train_labels
+ (t.nn.functional.logsigmoid(pred) - pred) * (1 - train_labels)
)
losses += loss
return losses / num_examples
def corn_label_from_logits(logits):
"""
Returns the predicted rank label from logits for a
network trained via the CORN loss.
Parameters
----------
logits : torch.tensor, shape=(n_examples, n_classes)
Torch tensor consisting of logits returned by the
neural net.
Returns
----------
labels : torch.tensor, shape=(n_examples)
Integer tensor containing the predicted rank (class) labels
Examples
----------
>>> # 2 training examples, 5 classes
>>> logits = torch.tensor([[14.152, -6.1942, 0.47710, 0.96850],
... [65.667, 0.303, 11.500, -4.524]])
>>> corn_label_from_logits(logits)
tensor([1, 3])
https://github.com/Raschka-research-group/coral-pytorch/blob/c6ab93afd555a6eac708c95ae1feafa15f91c5aa/coral_pytorch/dataset.py
"""
probas = t.sigmoid(logits)
probas = t.cumprod(probas, dim=1)
predict_levels = probas > 0.5
predicted_labels = t.sum(predict_levels, dim=1)
return predicted_labels
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