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\renewcommand{\FIGREP}{src/mpi/figures}
\section{Message Passing Interface (MPI)}
\label{sec:mpi}
\intersec{deneb}
\begin{frame}
\frametitle{MPI}
\framesubtitle{Goals of this section}
\begin{itemize}
\item Introduce distributed memory programming paradigm
\item Point-to-point communications
\item Collective communications
\end{itemize}
\end{frame}
\subsection{Introduction}
\begin{frame}
\frametitle{MPI}
\framesubtitle{Overview and goals of MPI}
\begin{itemize}
\item MPI is a \textit{Message-Passing Interface} specification
\item There are many implementations (MPICH, MVAPICH, Intel MPI, OpenMPI,
etc)
\item Library interface, not a programming language
\item It is standardized
\begin{itemize}
\item Defined by the \href{https://www.mpi-forum.org/}{MPI forum}
\item Current version is MPI 4.0
\end{itemize}
\item As such, it is portable, flexible and efficient
\item Interface to C and Fortran in standard
\end{itemize}
\end{frame}
\begin{frame}
\frametitle{MPI}
\framesubtitle{Message passing concepts}
\begin{itemize}
\item Let's derive a minimal message-passing interface
\item Message passing consists in transferring data chunks between separate
address spaces
\item Cooperative operation (\textit{send} matched with a \textit{receive}
operation)
\item From the sender:
\begin{itemize}
\item
\end{itemize}
\end{itemize}
\end{frame}
\subsection{MPI environment}
\begin{frame}[fragile]
\frametitle{MPI}
\framesubtitle{A simple hello world example}
\cxxfile[%
title={mpi/hello\_mpi.cc},
]{examples/mpi/hello_mpi.cc}
\end{frame}
\begin{frame}[b]
\frametitle{Environment}
\framesubtitle{}
\begin{itemize}
\item MPI code is bordered by a \cxxinline{MPI_Init} and a \cxxinline{MPI_Finalize}
\item MPI starts $N$ processes numbered $0, 1, ..., N-1$. It is the process \textit{rank}
\item They are grouped in a \textit{communicator} of \textit{size} $N$
\item After init, MPI provides a default communicator called \code{MPI\_COMM\_WORLD}
\end{itemize}
\addimage[width=7cm]{\FIGREP/communicator}{4.5cm}{3.2cm}
\end{frame}
\subsection{Terminology}
\begin{frame}
\frametitle{MPI}
\framesubtitle{}
\end{frame}
\subsection{Point-to-point communications}
\begin{frame}
\frametitle{MPI}
\framesubtitle{}
\end{frame}
\subsection{Collective communications}
\begin{frame}
\frametitle{MPI}
\framesubtitle{}
\end{frame}
\subsection{Advanced collective communications}
\begin{frame}
\frametitle{MPI}
\framesubtitle{}
\end{frame}
%%% Local Variables:
%%% mode: latex
%%% TeX-master: "../../phys_743_parallel_programming"
%%% End:
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