feat: add TimesNet_Q and xPatch models with Q matrix transformations

layers/revin.py

@@ -0,0 +1,61 @@
+import torch
+from torch import nn
+
+class RevIN(nn.Module):
+    def __init__(self, num_features: int, eps=1e-5, affine=True, subtract_last=False):
+        """
+        :param num_features: the number of features or channels
+        :param eps: a value added for numerical stability
+        :param affine: if True, RevIN has learnable affine parameters
+        """
+        super(RevIN, self).__init__()
+        self.num_features = num_features
+        self.eps = eps
+        self.affine = affine
+        self.subtract_last = subtract_last
+        if self.affine:
+            self._init_params()
+
+    def forward(self, x, mode:str):
+        if mode == 'norm':
+            self._get_statistics(x)
+            x = self._normalize(x)
+        elif mode == 'denorm':
+            x = self._denormalize(x)
+        else: raise NotImplementedError
+        return x
+
+    def _init_params(self):
+        # initialize RevIN params: (C,)
+        self.affine_weight = nn.Parameter(torch.ones(self.num_features))
+        self.affine_bias = nn.Parameter(torch.zeros(self.num_features))
+
+    def _get_statistics(self, x):
+        dim2reduce = tuple(range(1, x.ndim-1))
+        if self.subtract_last:
+            self.last = x[:,-1,:].unsqueeze(1)
+        else:
+            self.mean = torch.mean(x, dim=dim2reduce, keepdim=True).detach()
+        self.stdev = torch.sqrt(torch.var(x, dim=dim2reduce, keepdim=True, unbiased=False) + self.eps).detach()
+
+    def _normalize(self, x):
+        if self.subtract_last:
+            x = x - self.last
+        else:
+            x = x - self.mean
+        x = x / self.stdev
+        if self.affine:
+            x = x * self.affine_weight
+            x = x + self.affine_bias
+        return x
+
+    def _denormalize(self, x):
+        if self.affine:
+            x = x - self.affine_bias
+            x = x / (self.affine_weight + self.eps*self.eps)
+        x = x * self.stdev
+        if self.subtract_last:
+            x = x + self.last
+        else:
+            x =x + self.mean
+        return x