def test_device():
x = tensor([1, 2, 3], dtype="float32")
y1 = F.eye(x.shape, dtype="float32")
y2 = F.eye(x.shape, dtype="float32", device=None)
np.testing.assert_almost_equal(y1.numpy(), y2.numpy())
y3 = F.eye(x.shape, dtype="float32", device="xpux")
y4 = F.eye(x.shape, dtype="float32", device=x.device)
np.testing.assert_almost_equal(y3.numpy(), y4.numpy())
y5 = F.full((3, 2), 4, device=x.device)
y6 = F.full((3, 2), 4, device="xpux")
np.testing.assert_almost_equal(y5.numpy(), y6.numpy())
def fwd():
a = F.linspace(3, 10, 3, device=Device("xpux").to_c())
b = F.eye(3, device=Device("xpux").to_c())
return a, b
def forward(self, features, label=None, mask=None):
"""
if label and mask both None, the loss will degenerate to
SimSLR unsupervised loss.
Reference:
"A Simple Framework for Contrastive Learning of Visual Representations"<https://arxiv.org/pdf/2002.05709.pdf>
"Supervised Contrastive Learning"<https://arxiv.org/abs/2004.11362>
Args:
features(tensor): The embedding feature. shape=[bs, n_views, ...]
label(tensor): The label of images, shape=[bs]
mask(tensor): contrastive mask of shape [bsz, bsz], mask_{i,j}=1 if sample j
has the same class as sample i. Can be asymmetric.
return:
loss
"""
if len(features.shape) < 3:
raise ValueError("Features need have 3 dimensions at least")
bs, num_view = features.shape[:2]
#if dimension > 3, change the shape of the features to [bs, num_view, ...]
if len(features.shape) > 3:
features = features.reshape(bs, num_view, -1)
#label and mask cannot provided at the same time
if (label is not None) and (mask is not None):
raise ValueError("label and mask cannot provided at the same time")
elif (label is None) and (mask is None):
mask = F.eye(bs, dtype="float32")
elif label is not None:
label = label.reshape(-1, 1)
if label.shape[0] != bs:
raise RuntimeError(
"Num of labels does not match num of features")
mask = F.equal(label, label.T)
else:
mask = mask.astype("float32")
contrast_count = features.shape[1]
features = F.split(features, features.shape[1], axis=1)
contrast_feature = F.squeeze(F.concat(features, axis=0), axis=1)
if self.contrast_mode == "one":
anchor_feature = features[:, 0]
anchor_count = 1
elif self.contrast_mode == "all":
anchor_feature = contrast_feature
anchor_count = contrast_count
else:
raise ValueError("Unknown mode:{}".format(self.contrast_mode))
#compute logits
anchor_dot_contrast = F.div(
F.matmul(anchor_feature, contrast_feature.T), self.temperate)
#for numerical stability
logits_max = F.max(anchor_dot_contrast, axis=-1, keepdims=True)
logits = anchor_dot_contrast - logits_max
#tile mask
an1, con = mask.shape[:2]
nums = anchor_count * contrast_count
# mask-out self-contrast cases
mask = F.stack([mask] * nums).reshape(an1 * anchor_count,
con * contrast_count)
logits_mask = F.scatter(
F.ones_like(mask), 1,
F.arange(0, int(bs * anchor_count), dtype="int32").reshape(-1, 1),
F.zeros(int(bs * anchor_count), dtype="int32").reshape(-1, 1))
mask = mask * logits_mask
#compute log_prob
exp_logits = F.exp(logits) * logits_mask
log_prob = logits - F.log(F.sum(exp_logits, axis=1,
keepdims=True)) #equation 2
#mean
mean_log_prob_pos = F.sum(mask * log_prob, axis=1) / F.sum(mask,
axis=1)
#loss
loss = -(self.temperate / self.base_temperate) * mean_log_prob_pos
loss = F.mean(loss.reshape(anchor_count, bs))
return loss