diff --git a/llms/mlx_lm/models/mamba2.py b/llms/mlx_lm/models/mamba2.py index 5b97f7d9..0f1d89bc 100644 --- a/llms/mlx_lm/models/mamba2.py +++ b/llms/mlx_lm/models/mamba2.py @@ -140,9 +140,7 @@ class Mamba2Block(nn.Module): dt = proj[..., -self.n_heads:] # Process time steps - simplified to match PyTorch - dt = nn.softplus(dt + self.dt_bias) # Time steps may need scaling - dt = dt * (self.args.time_step_max - self.args.time_step_min) + self.args.time_step_min - dt = mx.minimum(mx.maximum(dt, self.args.time_step_floor), self.args.time_step_max) + dt = nn.softplus(dt + self.dt_bias) x_conv, conv_state = self.conv1d(x_conv, cache[0] if cache else None) if cache is not None: @@ -151,9 +149,8 @@ class Mamba2Block(nn.Module): # Split conv output and reshape x = x_conv[..., :self.d_inner] - x = mx.reshape(x, (batch_size, seq_len, self.n_heads, self.d_head)) - B = mx.reshape(x_conv[..., self.d_inner:self.d_inner + self.d_state], (batch_size, seq_len, self.n_heads, self.d_state // self.n_heads)) - C = mx.reshape(x_conv[..., -self.d_state:], (batch_size, seq_len, self.n_heads, self.d_state // self.n_heads)) + B = mx.reshape(x_conv[..., self.d_inner:self.d_inner + self.n_groups * self.d_state], (batch_size, seq_len, self.n_groups, -1)) + C = mx.reshape(x_conv[..., -self.n_groups * self.d_state:], (batch_size, seq_len, self.n_groups, -1)) # Reshape for SSM processing x = mx.reshape(x, (batch_size, seq_len, self.n_heads, self.d_head)) @@ -161,12 +158,12 @@ class Mamba2Block(nn.Module): # Initialize state if cache and cache[1] is not None: # State initialization might need proper scaling - prev_state = cache[1] * self.args.initializer_range + prev_state = cache[1] else: prev_state = mx.zeros((batch_size, self.n_heads, self.d_head, self.d_state)) # Compute dA - simplified to match PyTorch - A = -mx.exp(self.A_log) * self.args.initializer_range + A = -mx.exp(self.A_log) dt = mx.reshape(dt, (batch_size, seq_len, self.n_heads)) dA = mx.exp(dt * mx.expand_dims(A, axis=(0, 1))) @@ -182,21 +179,18 @@ class Mamba2Block(nn.Module): dAt = dA[:, t] # [batch, n_heads] # Compute dBx using einsum to match PyTorch - dBx = mx.einsum('bh,bhd,bhp->bhpd', dAt, Bt, xt) - - # Update state - matches PyTorch implementation - next_state = ( - next_state * mx.expand_dims(dAt, axis=(-1, -2)) + dBx - ) - - # Compute output - yt = mx.einsum('bhpd,bhd->bhp', next_state, Ct) + dBx = mx.einsum('bh,bgd,bhp->bhpd', dAt, Bt, xt) # dAt: (b,h), Bt: (b,g,d), xt: (b,h,p) -> (b,h,p,d) + + # Update state + next_state = next_state * mx.expand_dims(dAt, axis=(-1, -2)) + dBx + + # Compute output with groups + yt = mx.einsum('bhpd,bgd->bhp', next_state, Ct) yt = yt + xt * mx.expand_dims(self.D, -1) # Reshape and normalize yt = mx.reshape(yt, (batch_size, 1, self.d_inner)) yt = self.norm(yt, z[:, t:t+1]) - yt = yt * (1.0 / math.sqrt(self.d_head)) outputs.append(self.out_proj(yt)) # Update cache