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@PotosnakW PotosnakW commented Mar 27, 2025

New files:

  • momentfm/models/moment.py: supports infini channel mixing with config.infini_channel_mixing boolean and config.n_series (number of individual time series). Only support forecasting currently.
  • momentfm/utils.t5_infini.py: contains 'T5InfiniModel' class. if config.infini_channel_mixing==True then T5InfiniAttention is used, else the default T5Attention is used.

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I checked the implementation with the paper and everything looks good! I left some minor stylistic comments + a small comment on positional bias. Additionally, it's good that infini-moment was moved to the other file.

"""

x_enc = self.tokenizer(x=x_enc)
batch_size, n_channels, seq_len = x_enc.shape
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I suggest unifying n_channels and n_series.

x: [batch_size x n_channels x n_patches x d_model]
output: [batch_size x n_channels x forecast_horizon]
"""
x = self.flatten(x) # x: [batch_size, n_series, n_patches, d_model]
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suggesting unification of n_channels and n_series

if not self.has_relative_attention_bias:
position_bias = torch.zeros(
(1, self.n_channels, self.n_heads, seq_length, key_length), device=hidden_states.device, dtype=hidden_states.dtype
) # Willa - should we use n_channels or just 1?
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in the original implementation by Nina there is no channel axis, so it gets probably broadcasted and position biases are shared between channels, hence there should be probably 1?

# Vectorized infini attention computation across channels
sigma_k = self.elu(key_states) + 1.0 # [batch_size, n_series, n_heads, n_patch, dim]
sigma_k_transposed = sigma_k.transpose(-2, -1) # [batch_size, n_series, n_heads, dim, n_patch]
memory_matrix = torch.matmul(sigma_k_transposed, value_states).sum(dim=1).unsqueeze(1) # [batch_size, 1, n_heads, dim, dim] sum over channels then unsqueeze to enable broadcasting over channels
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for the purpose of making it easier to understand- can we split the computation of memory matrix into memory updates and only then sum them in the separate line? Implementation looks correct btw!

z = sigma_k.sum(dim=-2).unsqueeze(-1).sum(dim=1) # [batch_size, n_heads, dim, 1] sum over sequence length and channels
z = z.unsqueeze(dim=1) # [batch_size, 1, n_heads, dim, 1]
sigma_q = self.elu(query_states) + 1.0 # [batch_size, n_series, n_heads, n_patch, dim]
A_mem = (sigma_q @ memory_matrix) / ((sigma_q @ z) + 1e-6) # [batch_size, n_series, n_heads, n_patch, dim]/[batch_size, n_series, n_heads, n_patch, 1] --> [batch_size, n_series, n_heads, n_patch, dim] Adding 1e-6 for preventing division to 0
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maybe split this too?

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2 participants