first commit

layers/AutoCorrelation.py

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+import torch
+import torch.nn as nn
+import torch.nn.functional as F
+import matplotlib.pyplot as plt
+import numpy as np
+import math
+from math import sqrt
+import os
+
+
+class AutoCorrelation(nn.Module):
+    """
+    AutoCorrelation Mechanism with the following two phases:
+    (1) period-based dependencies discovery
+    (2) time delay aggregation
+    This block can replace the self-attention family mechanism seamlessly.
+    """
+
+    def __init__(self, mask_flag=True, factor=1, scale=None, attention_dropout=0.1, output_attention=False):
+        super(AutoCorrelation, self).__init__()
+        self.factor = factor
+        self.scale = scale
+        self.mask_flag = mask_flag
+        self.output_attention = output_attention
+        self.dropout = nn.Dropout(attention_dropout)
+
+    def time_delay_agg_training(self, values, corr):
+        """
+        SpeedUp version of Autocorrelation (a batch-normalization style design)
+        This is for the training phase.
+        """
+        head = values.shape[1]
+        channel = values.shape[2]
+        length = values.shape[3]
+        # find top k
+        top_k = int(self.factor * math.log(length))
+        mean_value = torch.mean(torch.mean(corr, dim=1), dim=1)
+        index = torch.topk(torch.mean(mean_value, dim=0), top_k, dim=-1)[1]
+        weights = torch.stack([mean_value[:, index[i]] for i in range(top_k)], dim=-1)
+        # update corr
+        tmp_corr = torch.softmax(weights, dim=-1)
+        # aggregation
+        tmp_values = values
+        delays_agg = torch.zeros_like(values).float()
+        for i in range(top_k):
+            pattern = torch.roll(tmp_values, -int(index[i]), -1)
+            delays_agg = delays_agg + pattern * \
+                         (tmp_corr[:, i].unsqueeze(1).unsqueeze(1).unsqueeze(1).repeat(1, head, channel, length))
+        return delays_agg
+
+    def time_delay_agg_inference(self, values, corr):
+        """
+        SpeedUp version of Autocorrelation (a batch-normalization style design)
+        This is for the inference phase.
+        """
+        batch = values.shape[0]
+        head = values.shape[1]
+        channel = values.shape[2]
+        length = values.shape[3]
+        # index init
+        init_index = torch.arange(length).unsqueeze(0).unsqueeze(0).unsqueeze(0).repeat(batch, head, channel, 1).to(values.device)
+        # find top k
+        top_k = int(self.factor * math.log(length))
+        mean_value = torch.mean(torch.mean(corr, dim=1), dim=1)
+        weights, delay = torch.topk(mean_value, top_k, dim=-1)
+        # update corr
+        tmp_corr = torch.softmax(weights, dim=-1)
+        # aggregation
+        tmp_values = values.repeat(1, 1, 1, 2)
+        delays_agg = torch.zeros_like(values).float()
+        for i in range(top_k):
+            tmp_delay = init_index + delay[:, i].unsqueeze(1).unsqueeze(1).unsqueeze(1).repeat(1, head, channel, length)
+            pattern = torch.gather(tmp_values, dim=-1, index=tmp_delay)
+            delays_agg = delays_agg + pattern * \
+                         (tmp_corr[:, i].unsqueeze(1).unsqueeze(1).unsqueeze(1).repeat(1, head, channel, length))
+        return delays_agg
+
+    def time_delay_agg_full(self, values, corr):
+        """
+        Standard version of Autocorrelation
+        """
+        batch = values.shape[0]
+        head = values.shape[1]
+        channel = values.shape[2]
+        length = values.shape[3]
+        # index init
+        init_index = torch.arange(length).unsqueeze(0).unsqueeze(0).unsqueeze(0).repeat(batch, head, channel, 1).to(values.device)
+        # find top k
+        top_k = int(self.factor * math.log(length))
+        weights, delay = torch.topk(corr, top_k, dim=-1)
+        # update corr
+        tmp_corr = torch.softmax(weights, dim=-1)
+        # aggregation
+        tmp_values = values.repeat(1, 1, 1, 2)
+        delays_agg = torch.zeros_like(values).float()
+        for i in range(top_k):
+            tmp_delay = init_index + delay[..., i].unsqueeze(-1)
+            pattern = torch.gather(tmp_values, dim=-1, index=tmp_delay)
+            delays_agg = delays_agg + pattern * (tmp_corr[..., i].unsqueeze(-1))
+        return delays_agg
+
+    def forward(self, queries, keys, values, attn_mask):
+        B, L, H, E = queries.shape
+        _, S, _, D = values.shape
+        if L > S:
+            zeros = torch.zeros_like(queries[:, :(L - S), :]).float()
+            values = torch.cat([values, zeros], dim=1)
+            keys = torch.cat([keys, zeros], dim=1)
+        else:
+            values = values[:, :L, :, :]
+            keys = keys[:, :L, :, :]
+
+        # period-based dependencies
+        q_fft = torch.fft.rfft(queries.permute(0, 2, 3, 1).contiguous(), dim=-1)
+        k_fft = torch.fft.rfft(keys.permute(0, 2, 3, 1).contiguous(), dim=-1)
+        res = q_fft * torch.conj(k_fft)
+        corr = torch.fft.irfft(res, dim=-1)
+
+        # time delay agg
+        if self.training:
+            V = self.time_delay_agg_training(values.permute(0, 2, 3, 1).contiguous(), corr).permute(0, 3, 1, 2)
+        else:
+            V = self.time_delay_agg_inference(values.permute(0, 2, 3, 1).contiguous(), corr).permute(0, 3, 1, 2)
+
+        if self.output_attention:
+            return (V.contiguous(), corr.permute(0, 3, 1, 2))
+        else:
+            return (V.contiguous(), None)
+
+
+class AutoCorrelationLayer(nn.Module):
+    def __init__(self, correlation, d_model, n_heads, d_keys=None,
+                 d_values=None):
+        super(AutoCorrelationLayer, self).__init__()
+
+        d_keys = d_keys or (d_model // n_heads)
+        d_values = d_values or (d_model // n_heads)
+
+        self.inner_correlation = correlation
+        self.query_projection = nn.Linear(d_model, d_keys * n_heads)
+        self.key_projection = nn.Linear(d_model, d_keys * n_heads)
+        self.value_projection = nn.Linear(d_model, d_values * n_heads)
+        self.out_projection = nn.Linear(d_values * n_heads, d_model)
+        self.n_heads = n_heads
+
+    def forward(self, queries, keys, values, attn_mask):
+        B, L, _ = queries.shape
+        _, S, _ = keys.shape
+        H = self.n_heads
+
+        queries = self.query_projection(queries).view(B, L, H, -1)
+        keys = self.key_projection(keys).view(B, S, H, -1)
+        values = self.value_projection(values).view(B, S, H, -1)
+
+        out, attn = self.inner_correlation(
+            queries,
+            keys,
+            values,
+            attn_mask
+        )
+        out = out.view(B, L, -1)
+
+        return self.out_projection(out), attn