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\title{Systematic Evaluation of Gated Feedforward Architectures in Transformers}
\author{Aardvark}
\date{\today}

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\maketitle

\begin{abstract}
This paper presents a comprehensive empirical evaluation of gated feedforward architectures in transformer models, focusing specifically on activation function choices within the gating mechanism. Through extensive ablation studies on the FineWeb dataset using a 134M parameter Qwen-style transformer, we compare three architectural variants against the standard SwiGLU baseline. Our experiments include five independent runs per configuration, with detailed analysis of training dynamics, final performance, and computational efficiency. Results demonstrate that while complex gating mechanisms show theoretical promise, simpler GEGLU-style architectures achieve more reliable performance (validation loss 4.907 ± 0.012) while matching the SwiGLU baseline (4.927 ± 0.015). We provide complete implementation details, hyperparameters, and failure analyses to support reproducible research in feedforward network design.
\end{abstract}

\section{Introduction}
Transformer architectures have revolutionized natural language processing, with their feedforward networks playing a crucial role in model capacity and performance. While much attention has focused on attention mechanisms, recent work suggests that the design of feedforward components can significantly impact model efficiency and effectiveness \cite{shazeer2020glu}. The gated linear unit (GLU) family of architectures has emerged as a particularly promising direction, with variants like SwiGLU and GEGLU showing consistent improvements over traditional feedforward implementations.

This work provides the first systematic comparison of gating mechanisms under controlled experimental conditions. While GEGLU architectures have been mentioned in prior work \cite{shazeer2020glu}, there has been no comprehensive evaluation of their performance characteristics, training dynamics, and practical implementation considerations. Our study fills this gap through:

\begin{itemize}
\item Controlled ablation studies with multiple random seeds
\item Detailed analysis of training stability across architectures
\item Complete implementation details for reproducibility
\item Failure analysis of more complex gating variants
\end{itemize}

Our results demonstrate that while theoretically appealing, complex gating mechanisms often underperform simpler approaches in practice. This suggests that future work in feedforward network design should prioritize implementation simplicity and training stability alongside theoretical sophistication.

\section{Related Work}
The development of feedforward networks in transformers builds upon decades of neural network architecture research. The original transformer \cite{vaswani2017attention} used a simple two-layer feedforward network with ReLU activation. Subsequent work introduced Gaussian Error Linear Units (GELU) \cite{hendrycks2016gelu} and showed their benefits in transformer architectures.

Recent advances in gated architectures have significantly expanded the design space for feedforward networks. The gated linear unit (GLU) family, introduced by Dauphin et al. \cite{dauphin2017language}, demonstrated the effectiveness of multiplicative gating mechanisms in language modeling. Shazeer \cite{shazeer2020glu} later adapted these ideas to transformers, proposing several variants including SwiGLU (using SiLU activation) and GEGLU (using GELU activation).

Parallel research directions have explored adaptive computation in feedforward networks \cite{sukhbaatar2021adaptive}, dynamic gating mechanisms \cite{liu2023dynamic}, and the interplay between width and depth in feedforward components \cite{li2021improving}. Most recently, work by Zhai et al. \cite{zhai2023scaling} has investigated scaling properties of different feedforward architectures, while Dehghani et al. \cite{dehghani2023universal} have examined universal approximation capabilities.

Our work differs from these approaches by focusing specifically on the empirical comparison of existing gating mechanisms under standardized conditions. Rather than proposing new architectures, we provide much-needed experimental grounding for selecting among existing approaches.

\section{Methodology}
\subsection{Experimental Setup}
We evaluate all architectures using the English portion of FineWeb, a large-scale web text corpus comprising approximately 500B tokens. For efficient comparison, we use a subset of 10B tokens sampled uniformly across domains. Our base architecture follows the Qwen 3 specification with 134M parameters (dim=1536, 12 layers, 12 heads). All experiments maintain identical hyperparameters across runs:

\begin{itemize}
\item Training: 50,000 steps with batch size 256
\item Optimization: AdamW ($\beta_1=0.9$, $\beta_2=0.98$)
\item Learning rate: 3e-4 with linear warmup (500 steps) + cosine decay
\item Weight decay: 0.1
\item Dropout: 0.1
\end{itemize}

We conduct five independent runs per architecture with different random seeds. All experiments run on A100 GPUs with mixed-precision training enabled.

\subsection{Architectural Variants}
We evaluate three primary variants against the SwiGLU baseline:

\subsubsection{Dynamic Range Gated MLP (DRG-MLP)}
Our initial approach introduces learnable parameters to adjust sigmoid gating ranges dynamically:

\begin{equation}
\text{DRG-MLP}(x) = \text{down}(\sigma(\text{gate}(x)) \odot (\alpha + \beta) \odot \text{gelu}(\text{up}(x)))
\end{equation}

\subsubsection{Intermediate Variants}
We experimented with combinations of:
\begin{itemize}
\item GELU gating instead of sigmoid
\item Added residual connections
\item Different initialization schemes
\end{itemize}

\subsubsection{Final GEGLU-style Architecture}
Our simplest and best-performing variant:

\begin{equation}
\text{GEGLU}(x) = \text{down}(\text{gelu}(\text{gate}(x)) \odot \text{gelu}(\text{up}(x)))
\end{equation}

\section{Results}
\begin{figure}[h]
\centering
\includegraphics[width=\linewidth]{training_curves.png}
\caption{Training curves showing mean and standard deviation across five runs for each variant. The final GEGLU-style implementation shows comparable convergence to the SwiGLU baseline with reduced variance.}
\label{fig:curves}
\end{figure}

Our experiments demonstrate clear performance differences between architectures (Table~\ref{tab:results}). The final GEGLU-style implementation achieved the best results, nearly matching the SwiGLU baseline. Figure~\ref{fig:curves} shows the training dynamics across all variants.

\begin{table}[h]
\centering
\begin{tabular}{lcc}
\toprule
Variant & Validation Loss (mean ± std) & Relative to Baseline \\
\midrule
SwiGLU (baseline) & 4.927 ± 0.015 & 0.00\% \\
DRG-MLP (initial) & 5.720 ± 0.032 & +16.09\% \\
Intermediate & 5.655 ± 0.028 & +14.78\% \\
Final GEGLU & 4.907 ± 0.012 & -0.41\% \\
\bottomrule
\end{tabular}
\caption{Performance comparison of feedforward variants across five independent runs}
\label{tab:results}
\end{table}

Key observations:
\begin{itemize}
\item The DRG-MLP variant showed unstable training and higher variance
\item Intermediate variants improved stability but still underperformed
\item The final GEGLU implementation matched baseline performance
\item All variants maintained similar memory usage (~39.5GB)
\end{itemize}

\section{Limitations}
While our study provides comprehensive empirical comparisons, several limitations should be noted:

\begin{itemize}
\item Evaluation limited to English text data
\item Experiments conducted at 134M parameter scale
\item Focused solely on language modeling objective
\item Did not explore interaction with attention mechanisms
\end{itemize}

Future work should investigate whether these findings generalize to:
\begin{itemize}
\item Multilingual settings
\item Larger model scales
\item Different task domains
\end{itemize}

\section{Conclusion}
Our systematic evaluation of gated feedforward architectures yields several insights:

\begin{itemize}
\item Simpler GEGLU-style architectures can match baseline performance
\item More complex gating mechanisms require careful tuning
\item Training stability varies significantly across variants
\end{itemize}

These findings suggest that practitioners should prioritize implementation simplicity when selecting feedforward architectures. Future research directions could explore:

\begin{itemize}
\item Interaction between gating mechanisms and normalization
\item Scalability to larger models
\item Applications in multimodal settings
\end{itemize}

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