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# Copyright (c) 2023, Dan Fu and Simran Arora.
# Adapted from https://github.com/HazyResearch/safari/blob/main/src/models/sequence/hyena.py
import torch.nn as nn
from einops import rearrange
import opt_einsum as oe
contract = oe.contract
from .hyena_utils import HyenaFilter
class MonarchMixerSequenceMixing(nn.Module):
def __init__(
self,
d_model,
l_max=128,
dropout=0.0,
hyena_kernel_lr=None,
bidirectional=False,
hyena_lr_pos_emb=1e-5,
hyena_w=10,
hyena_w_mod=1,
hyena_wd=0.1,
hyena_emb_dim=3,
hyena_filter_dropout=0.0,
hyena_filter_order=16,
residual_long_conv=False,
):
super().__init__()
self.d_model = d_model
self.l_max = l_max
self.kernel_lr = hyena_kernel_lr
self.channels = 1
self.bidirectional = bidirectional
self.residual_long_conv = residual_long_conv
self.NUM_PROJECTIONS = 3
print('-- Bidirectional:', self.bidirectional)
print("-- Using Long Conv Residual:", self.residual_long_conv)
print('-- Hyena w:', hyena_w)
print('-- Hyena w mod:', hyena_w_mod)
print(f"-- Hyena filter order: {hyena_filter_order}")
print(f"-- Hyena filter dropout: {hyena_filter_dropout}")
print(f"-- Hyena filter wd: {hyena_wd}")
print(f"-- Hyena filter emb dim: {hyena_emb_dim}")
print(f"-- Hyena filter lr: {hyena_kernel_lr}")
print(f"-- Hyena filter lr pos emb: {hyena_lr_pos_emb}")
self.filter_fn = HyenaFilter(
self.d_model,
order=hyena_filter_order,
seq_len=self.l_max,
dropout=hyena_filter_dropout,
bidirectional=self.bidirectional,
lr=hyena_kernel_lr,
lr_pos_emb=hyena_lr_pos_emb,
w=hyena_w, # frequency of periodic activations
w_mod=hyena_w_mod,
wd=hyena_wd, # weight decay of kernel parameters
emb_dim=hyena_emb_dim,
)
if self.residual_long_conv:
self.filter_fn2 = HyenaFilter(
self.d_model,
order=hyena_filter_order,
seq_len=self.l_max,
dropout=hyena_filter_dropout,
bidirectional=self.bidirectional,
lr=hyena_kernel_lr,
lr_pos_emb=hyena_lr_pos_emb,
w=hyena_w, # frequency of periodic activations
w_mod=hyena_w_mod,
wd=hyena_wd, # weight decay of kernel parameters
emb_dim=hyena_emb_dim,
)
# setup projections
self.in_linear = nn.Linear(d_model, 3 * d_model)
self.out_linear = nn.Linear(d_model, d_model)
# setup short conv
total_width = self.d_model * self.NUM_PROJECTIONS
self.short_filter = nn.Conv1d(
in_channels=total_width,
out_channels=total_width,
kernel_size=3,
groups=total_width,
padding=2,
)
def forward(self, u, **kwargs):
# u is B L H
L = u.size(-2)
# in projection
u_orig = u
u = self.in_linear(u)
u = rearrange(u, "b l d -> b d l")
# short filter
uc = self.short_filter(u)[..., :L]
x1, x2, v = uc.split(self.d_model, dim=1)
v = v * x1
k = self.filter_fn.filter(L, device=u.device)
k = rearrange(k, "c l d -> c d l")[0] # `c` is always 1 by default
if self.bidirectional:
k_rev = self.filter_fn.filter_rev(L, device=u.device)
k_rev = rearrange(k_rev, "c l d -> c d l")[0] # `c` is always 1 by default
else:
k_rev = None
y = self.filter_fn(v, L, k_fwd=k, k_rev=k_rev, bias= self.filter_fn.bias[None, :, None])
if self.residual_long_conv:
k2 = self.filter_fn2.filter(L, device=u.device)
k2 = rearrange(k2, "c l d -> c d l")[0]
if self.bidirectional:
k2_rev = self.filter_fn2.filter_rev(L, device=u.device)
k2_rev = rearrange(k2_rev, "c l d -> c d l")[0] # `c` is always 1 by default
else:
k2_rev = None
yu = self.filter_fn2(u_orig.transpose(-1, -2), L, k_fwd=k2, k_rev=k2_rev, bias= self.filter_fn2.bias[None, :, None])
# post gating
y = y * x2
if self.residual_long_conv:
y = y + yu
y = y.transpose(-1, -2)
y = self.out_linear(y)
return y, None
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