Function simd_adamw_update 

pub fn simd_adamw_update(
    grad: &[f32],
    m: &mut [f32],
    v: &mut [f32],
    param: &mut [f32],
    beta1: f32,
    beta2: f32,
    lr: f32,
    lr_t: f32,
    weight_decay: f32,
    epsilon: f32,
)

Fused AdamW parameter update with decoupled weight decay.

Updates momentum, variance, and parameters in a single pass with zero temporary allocations.

Arguments

• grad - Gradient vector
• m - First moment (momentum) vector (updated in-place)
• v - Second moment (variance) vector (updated in-place)
• param - Parameter vector (updated in-place)
• beta1 - Momentum decay rate
• beta2 - Variance decay rate
• lr - Learning rate
• lr_t - Bias-corrected learning rate for adaptive update
• weight_decay - Weight decay coefficient
• epsilon - Small constant for numerical stability