Add content src/site/notes/AI/torch/nn/linear.md

src/site/notes/AI/torch/nn/linear.md

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+---
+{"dg-publish":true,"permalink":"/AI/torch/nn/linear/","noteIcon":"3"}
+---
+
+#linear
+
+https://pytorch.org/docs/stable/generated/torch.nn.Linear.html
+
+Applies an affine linear transformation to the incoming data: 
+$$
+y=xA^{T} + b
+$$
+其中A和b分别是Linear中的weight和bias，这两个值会根据定义linear的in_features和out_features时确定shape，之后随机初始化，当然后也可以指定初始化算法，之后随模型训练更新weight
+
+```py
+import torch
+from torch import nn
+m = nn.Linear(3,4)
+print(m.weight)
+print(m.bias)
+
+input = torch.randn(3,3)
+output1 = m(input)
+
+output2 = torch.matmul(input, m.weight.t()) + m.bias
+
+assert output1 == output2
+
+```