# Built on top of the original implementation at https://github.com/ArrowLuo/CLIP4Clip
#
# Modifications by Copyright 2022 Zilliz. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""PyTorch BERT model."""
import torch
import torch.nn.functional as F
from torch import nn
[docs]class LayerNorm(nn.Module):
"""
Layer normalization component.
"""
[docs] def __init__(self, hidden_size, eps=1e-12):
"""Construct a layernorm module in the TF style (epsilon inside the square root).
"""
super().__init__()
self.weight = nn.Parameter(torch.ones(hidden_size))
self.bias = nn.Parameter(torch.zeros(hidden_size))
self.variance_epsilon = eps
[docs] def forward(self, x):
u = x.mean(-1, keepdim=True)
s = (x - u).pow(2).mean(-1, keepdim=True)
x = (x - u) / torch.sqrt(s + self.variance_epsilon)
return self.weight * x + self.bias
[docs]class PreTrainedModel(nn.Module):
""" An abstract class to handle weights initialization and
a simple interface for dowloading and loading pretrained models.
"""
[docs] def init_weights(self, module):
""" Initialize the weights.
"""
if isinstance(module, (nn.Linear, nn.Embedding)):
# Slightly different from the TF version which uses truncated_normal for initialization
# cf https://github.com/pytorch/pytorch/pull/5617
module.weight.data.normal_(mean=0.0, std=0.02)
elif isinstance(module, LayerNorm):
if "beta" in dir(module) and "gamma" in dir(module):
module.beta.data.zero_()
module.gamma.data.fill_(1.0)
else:
module.bias.data.zero_()
module.weight.data.fill_(1.0)
if isinstance(module, nn.Linear) and module.bias is not None:
module.bias.data.zero_()
[docs]class CrossEn(nn.Module):
[docs] def forward(self, sim_matrix):
logpt = F.log_softmax(sim_matrix, dim=-1)
logpt = torch.diag(logpt)
nce_loss = -logpt
sim_loss = nce_loss.mean()
return sim_loss
