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% MLSys·im Tutorial — Module 3: Scale, Dollars, and Carbon
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  chapter      = {Module 3},
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  chaptertitle = {MLSys·im: Scale, Dollars, and Carbon},
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\title{MLSys·im Tutorial --- Module 3}
\subtitle{Scale, Dollars, and Carbon}
\author{Vijay Janapa Reddi}
\institute{Harvard University}
\date{Conference Tutorial}

\begin{document}

\begin{frame}[plain,shrink=10]
  \titlepage
\end{frame}

\begin{frame}{Roadmap: Conference Tutorial}
\centering\small
\begin{tabular}{rll}
\toprule
\textbf{Module} & \textbf{Topic} & \textbf{Status} \\
\midrule
Module 1 & Foundations \& Architecture & \checkmark Done \\
Module 2 & Advanced Single-Node Analysis & \checkmark Done \\
\rowcolor{crimson!12}
\textbf{Module 3} & \textbf{Scale, Dollars, and Carbon} & \textbf{$\leftarrow$ You are here} \\
Module 4 & Design Space Exploration \& Synthesis & \\
\bottomrule
\end{tabular}
\end{frame}

\section{Going Distributed}

\begin{frame}{The Distributed Computing Taxonomy}
When models outgrow a single GPU, we must partition them:
\begin{itemize}
  \item \textbf{Data Parallelism (DP):} Replicate model, shard data.
  \item \textbf{Tensor Parallelism (TP):} Shard matrix multiplications. High communication bandwidth required (NVLink).
  \item \textbf{Pipeline Parallelism (PP):} Shard layers across GPUs. Leads to pipeline bubbles.
\end{itemize}
\end{frame}

\begin{frame}{The Amdahl Trap}
Scaling efficiency is never 100\%. It degrades due to:
\begin{enumerate}
  \item \textbf{Communication overhead:} Time spent passing tensors over InfiniBand (AllReduce, AllGather).
  \item \textbf{Pipeline bubbles:} GPUs sitting idle waiting for previous pipeline stages to finish.
  \item \textbf{Stragglers:} The cluster is only as fast as its slowest node.
\end{enumerate}
\vfill
\begin{center}
The \texttt{DistributedModel} solver automatically calculates network transmission times and pipeline bubbles.
\end{center}
\end{frame}

\section{Economics \& TCO}

\begin{frame}{The Total Cost of Ownership (TCO)}
\begin{center}
\Large
\[
\text{TCO} = \underbrace{\text{CapEx}}_{\text{hw + facility}}
          + \underbrace{\text{OpEx}_{\text{energy}}}_{\text{electricity}}
          + \underbrace{\text{OpEx}_{\text{maint}}}_{\text{staff}}
\]
\end{center}
\vspace{1em}
\textbf{The Infrastructure Multiplier:}
GPUs are only $\sim$40\% of total CapEx. Networking (InfiniBand), power delivery, cooling, facility, and operations add 50--150\%.
\end{frame}

\section{Sustainability \& Composition}

\begin{frame}[fragile]{Cross-Domain Carbon Accounting}
\small
Training time depends on hardware efficiency; carbon depends on grid intensity.
\begin{lstlisting}[language=Python,basicstyle=\ttfamily\tiny]
from mlsysim.solvers import DistributedModel, SustainabilityModel
from mlsysim.systems.registry import Systems
from mlsysim.infrastructure.registry import Infrastructure
from mlsysim.models.registry import Models

fleet = Systems.Clusters.Research_256  # 32x DGX H100 nodes

perf = DistributedModel().solve(
    model=Models.Language.Llama3_70B, fleet=fleet,
    tp_size=8, pp_size=1, dp_size=32)
days = perf.latency.to("days").magnitude

sust = SustainabilityModel().solve(
    fleet=fleet, duration_days=days, mfu=perf.mfu,
    datacenter=Infrastructure.Datacenters.GCP_Iowa)
print(f"Total Carbon: {sust.carbon_footprint:.1f} tonnes CO2e")
\end{lstlisting}
\end{frame}

\begin{frame}{Geography is the Biggest Lever}
\centering
\begin{tabular}{lcr}
\toprule
\textbf{Region} & \textbf{Mix} & \textbf{Carbon Intensity (gCO$_2$/kWh)} \\
\midrule
Quebec    & Hydro       & 20 \\
Sweden    & Hydro+Nuc   & 25 \\
US Avg    & Mixed       & 390 \\
Poland    & Coal        & 820 \\
\bottomrule
\end{tabular}
\vfill
\begin{alertblock}{The 41$\times$ Gap}
Training the exact same model on the exact same hardware in Poland emits \textbf{41$\times$ more carbon} than training it in Quebec.
\end{alertblock}
\end{frame}

\begin{frame}{Summary: Module 3}
\begin{enumerate}
  \item \textbf{Distributed Computing:} Tensor Parallelism requires high bandwidth (NVLink); Pipeline Parallelism incurs bubbles.
  \item \textbf{Economics:} Hardware is only 40\% of TCO. Do not ignore the Infrastructure Multiplier.
  \item \textbf{Composition:} Output from performance solvers (latency) pipes directly into sustainability and economics solvers.
  \item \textbf{Sustainability:} Geography (Carbon Intensity) is the single biggest lever in AI sustainability.
\end{enumerate}
\vspace{1em}
\begin{center}
\textit{Next up: Module 4 - Design Space Exploration!}
\end{center}
\end{frame}

\end{document}