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20120416-Nonblocking.tex
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20120416-Nonblocking.tex
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% \documentclass[handout]{beamer}
\documentclass{beamer}
\mode<presentation>
{
\usetheme{default}
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\setbeamercovered{transparent=100}
}
\usepackage[english]{babel}
\usepackage[latin1]{inputenc}
\usepackage{textpos,alltt,listings,multirow,ulem,siunitx}
\usepackage{pdfpages}
\usepackage{multimedia}
\newcommand\hmmax{0}
\newcommand\bmmax{0}
\usepackage{bm}
% font definitions, try \usepackage{ae} instead of the following
% three lines if you don't like this look
\usepackage{mathptmx}
\usepackage[scaled=.90]{helvet}
% \usepackage{courier}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary[shapes,shapes.arrows,arrows,shapes.misc,fit,positioning,trees,mindmap,backgrounds]
% \usepackage{pgfpages}
% \pgfpagesuselayout{4 on 1}[a4paper,landscape,border shrink=5mm]
\usepackage{JedMacros}
\title{User-defined Nonblocking Collectives \\ Must Make Progess}
\author{{\bf Jed Brown}}
% - Use the \inst command only if there are several affiliations.
% - Keep it simple, no one is interested in your street address.
\institute
{
{Mathematics and Computer Science Division, Argonne National Laboratory}
}
\date{Exascale Research Conference 2012-04-16}
% This is only inserted into the PDF information catalog. Can be left
% out.
\subject{Talks}
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% \pgfdeclareimage[height=0.5cm]{university-logo}{university-logo-filename}
% \logo{\pgfuseimage{university-logo}}
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% the beginning of each subsection:
% \AtBeginSubsection[]
% {
% \begin{frame}<beamer>
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% }
\AtBeginSection[]
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\begin{frame}<beamer>
\frametitle{Outline}
\tableofcontents[currentsection]
\end{frame}
}
% If you wish to uncover everything in a step-wise fashion, uncomment
% the following command:
% \beamerdefaultoverlayspecification{<+->}
\begin{document}
\lstset{language=C}
\normalem
\begin{frame}
\titlepage
\end{frame}
\begin{frame}{Blocking communication is the enemy}
\includegraphics{figures/PipelinedGMRES} \\
In PETSc, Block Jacobi with ILU preconditioning, {\tt -ksp\_type pgmres}
\end{frame}
\begin{frame}{Not all nonblocking algorithms belong ``upstream''}
\begin{itemize}
\item{\bf Tall skinny $QR$}
\begin{itemize}
\item Essentially {\tt Allreduce()} with side effects
\item In this case, needed to reconstruct orthogonal $Q$.
\end{itemize}
\item{\bf Unstructured communication setup}
\begin{itemize}
\item Neighbor discovery from one-sided specification
\item Sparse matrix assembly
\item Many AMR applications
\end{itemize}
\item{\bf Fast multipole method}
\begin{itemize}
\item Coarse levels have little computation
\item Can overlap with local work
\end{itemize}
\end{itemize}
\end{frame}
\begin{frame}{Ways to ensure progress}
\begin{itemize}
\item{\bf Just spawn a comm thread}
\begin{itemize}
\item Where should we put it?
\item Comm threads displace computation threads and compete for shared resources.
\item Many libraries with their own comm threads don't play nicely.
\end{itemize}
\item{\bf MPI Generalized Requests}
\begin{itemize}
\item Original MPI-2 had no way to have the request polled.
\item Latham, Gropp, Ross, and Thakur 2007 extended added an extension for polling, but only when \emph{that request} is tested.
\item MPI-3 nonblocking collectives are still ``special'' in that users cannot provide a nonblocking interface with comparable semantics.
\end{itemize}
\item{\bf Common event-driven interface}
\begin{itemize}
\item Could be a simple extension of MPI Generalized Requests.
\item Any new programming models should provide something comparable.
\end{itemize}
\end{itemize}
\end{frame}
\end{document}