def _MarginRankingLoss(input1, input2, target, margin = 0, reduction='mean'):
low_bound = flow.constant_like(target, 0, dtype= flow.float32)
if reduction == 'none':
ret = math.maximum(low_bound,
math.add(margin,math.multiply(target,math.multiply(-1,math.subtract(input1,input2)))))
else:
ret = math.reduce_mean(math.maximum(low_bound,
math.add(margin,math.multiply(target,math.multiply(-1,math.subtract(input1,input2))))))
return ret
def _MarginRankingLoss(self, input1, input2, target, reduction='mean'):
if reduction == 'none':
ret = flow.clip(
math.add(self.margin, math.multiply(target, math.multiply(-1, math.subtract(input1, input2)))),
min_value=0)
else:
ret = math.reduce_mean(flow.clip(
math.add(self.margin, math.multiply(target, math.multiply(-1, math.subtract(input1, input2)))),
min_value=0))
return ret
def forward(self, inputs, label):
"""
Args:
inputs (torch.Tensor): prediction matrix (before softmax) with
shape (batch_size, num_classes).
targets (torch.LongTensor): ground truth labels with shape (batch_size).
Each position contains the label index.
"""
one_hot_label = flow.one_hot(indices=flow.cast(label, flow.int32), depth=self.num_classes, axis=-1,
dtype=flow.float32)
log_probs = math.log(flow.nn.softmax(inputs, axis=1))
targets = math.add(math.multiply((1 - self.epsilon), one_hot_label), (self.epsilon / self.num_classes))
temp = math.multiply(log_probs, math.multiply(-1, targets))
temp2 = math.reduce_mean(temp, axis=0)
loss = math.reduce_sum(temp2)
return loss
def _euclidean_squared_distance(input1, input2):
"""Computes euclidean squared distance.
Args:
input1 : 2-D feature matrix.
input2 : 2-D feature matrix.
Returns:
distance matrix.
"""
m, n = input1.shape[0], input2.shape[0]
temp1 = math.reduce_sum(math.pow(
input1, flow.constant_like(input1, 2, dtype=flow.float32)),
axis=1)
temp2 = math.reduce_sum(math.pow(
input2, flow.constant_like(input2, 2, dtype=flow.float32)),
axis=1)
shape_tensor1 = flow.constant(value=0.0, dtype=flow.float32, shape=(m, n))
shape_tensor2 = flow.constant(value=0.0, dtype=flow.float32, shape=(n, m))
temp1 = flow.broadcast_like(temp1, like=shape_tensor1, broadcast_axes=[1])
temp2 = flow.transpose(flow.broadcast_like(temp2,
like=shape_tensor2,
broadcast_axes=[1]),
perm=(1, 0))
dismat = math.add(temp1, temp2)
return math.add(
dismat,
math.multiply(-2,
flow.matmul(input1, flow.transpose(input2,
perm=(1, 0)))))
def build(self, inputs, targets):
"""
Args:
inputs (torch.Tensor): feature matrix with shape (batch_size, feat_dim).
targets (torch.LongTensor): ground truth labels with shape (num_classes).
"""
n = inputs.shape[0]
dist = math.reduce_sum(math.pow(
inputs, flow.constant_like(inputs, 2, dtype=flow.float32)),
axis=1)
shape_tensor = flow.constant(value=0.0,
dtype=flow.float32,
shape=(n, n))
dist = flow.broadcast_like(dist, like=shape_tensor, broadcast_axes=[1])
dist = math.add(
dist, flow.transpose(dist, perm=(1, 0),
batch_axis_non_change=True))
temp1 = math.multiply(
-2,
flow.matmul(
inputs,
flow.transpose(inputs, perm=(1, 0),
batch_axis_non_change=True)))
dist = math.add(dist, temp1)
dist = math.sqrt(flow.clamp(dist, min_value=1e-12))
mask = math.equal(
flow.broadcast_like(targets, like=shape_tensor,
broadcast_axes=[1]),
flow.transpose(flow.broadcast_like(targets,
like=shape_tensor,
broadcast_axes=[1]),
perm=(1, 0),
batch_axis_non_change=True))
mask_rev = math.not_equal(
flow.broadcast_like(targets, like=shape_tensor,
broadcast_axes=[1]),
flow.transpose(flow.broadcast_like(targets,
like=shape_tensor,
broadcast_axes=[1]),
perm=(1, 0),
batch_axis_non_change=True))
dist_ap, dist_an = [], []
for i in range(n):
temp_dist = flow.slice_v2(dist, [(i, i + 1, 1)])
temp_mask = flow.slice_v2(mask, [(i, i + 1, 1)])
temp_mask_rev = flow.slice_v2(mask_rev, [(i, i + 1, 1)])
dist_ap.append(
math.reduce_max(
flow.gather_nd(temp_dist, flow.where(temp_mask))))
dist_an.append(
math.reduce_min(
flow.gather_nd(temp_dist, flow.where(temp_mask_rev))))
dist_ap = flow.concat(dist_ap, 0)
dist_an = flow.concat(dist_an, 0)
y = flow.ones_like(dist_an)
# return dist_an, dist_ap, y
return self._MarginRankingLoss(dist_an, dist_ap, y)