Premier jet pour les algos.

[loba-papers.git] / supercomp11 / supercomp11.tex

diff --git a/supercomp11/supercomp11.tex b/supercomp11/supercomp11.tex
index 2cc35eb0eb1c9d0411e2f26b5770144d18f256b3..472a724e88be8487149a813a776731b7585b11b1 100644 (file)
--- a/supercomp11/supercomp11.tex
+++ b/supercomp11/supercomp11.tex
@@ -5,9 +5,16 @@
 \usepackage{amsmath}
 \usepackage{courier}
 \usepackage{graphicx}
 \usepackage{amsmath}
 \usepackage{courier}
 \usepackage{graphicx}

+\usepackage[ruled,lined]{algorithm2e}

 
 \newcommand{\abs}[1]{\lvert#1\rvert} % \abs{x} -> |x|
 
 
 \newcommand{\abs}[1]{\lvert#1\rvert} % \abs{x} -> |x|
 

+\newenvironment{algodata}{%
+  \begin{tabular}[t]{@{}l@{:~}l@{}}}{%
+  \end{tabular}}
+
+\newcommand{\VAR}[1]{\textit{#1}}
+

 \begin{document}
 
 \title{Best effort strategy and virtual load
 \begin{document}
 
 \title{Best effort strategy and virtual load


@@ -273,10 +280,10 @@ use this concept, load balancing messages must be sent using two different kinds
 of  messages:  load information  messages  and  load  balancing messages.   More
 precisely, a node  wanting to send a part  of its load to one  of its neighbors,
 can first send  a load information message containing the load  it will send and
 of  messages:  load information  messages  and  load  balancing messages.   More
 precisely, a node  wanting to send a part  of its load to one  of its neighbors,
 can first send  a load information message containing the load  it will send and

-then it  can send the load  balancing message containing data  to be transfered.
+then it can send the load  balancing message containing data  to be transferred.

 Load information  message are really  short, consequently they will  be received
 very quickly.  In opposition, load  balancing messages are often bigger and thus
 Load information  message are really  short, consequently they will  be received
 very quickly.  In opposition, load  balancing messages are often bigger and thus

-require more time to be transfered.
+require more time to be transferred.

 
 The  concept  of  \texttt{virtual load}  allows  a  node  that received  a  load
 information message to integrate the load that it will receive later in its load
 
 The  concept  of  \texttt{virtual load}  allows  a  node  that received  a  load
 information message to integrate the load that it will receive later in its load


@@ -333,14 +340,38 @@ a \emph{receiving thread}, a \emph{computing thread}, and a
 
 \paragraph{Receiving thread} The receiving thread is in charge of
 waiting for messages to come, either on the control channel, or on the
 
 \paragraph{Receiving thread} The receiving thread is in charge of
 waiting for messages to come, either on the control channel, or on the

-data channel.  When a message is received, it is pushed in a buffer of
+data channel.  Its behavior is sketched by Algorithm~\ref{algo.recv}.
+When a message is received, it is pushed in a buffer of

 received message, to be later consumed by one of the other threads.
 There are two such buffers, one for the control messages, and one for
 the data messages.  The buffers are implemented with a lock-free FIFO
 \cite{sutter.2008.writing} to avoid contention between the threads.
 
 received message, to be later consumed by one of the other threads.
 There are two such buffers, one for the control messages, and one for
 the data messages.  The buffers are implemented with a lock-free FIFO
 \cite{sutter.2008.writing} to avoid contention between the threads.
 

+\begin{algorithm}
+  \caption{Receiving thread}
+  \label{algo.recv}
+  \KwData{
+    \begin{algodata}
+      \VAR{ctrl\_chan}, \VAR{data\_chan}
+      & communication channels (control and data) \\
+      \VAR{ctrl\_fifo}, \VAR{data\_fifo}
+      & buffers of received messages (control and data) \\
+    \end{algodata}}
+  \While{true}{%
+    wait for a message to be available on either \VAR{ctrl\_chan},
+    or \VAR{data\_chan}\;
+    \If{a message is available on \VAR{ctrl\_chan}}{%
+      get the message from \VAR{ctrl\_chan}, and push it into \VAR{ctrl\_fifo}\;
+    }
+    \If{a message is available on \VAR{data\_chan}}{%
+      get the message from \VAR{data\_chan}, and push it into \VAR{data\_fifo}\;
+    }
+  }
+\end{algorithm}
+

 \paragraph{Computing thread} The computing thread is in charge of the
 \paragraph{Computing thread} The computing thread is in charge of the

-real load management.  It iteratively runs the following operations:
+real load management.  As exposed in Algorithm~\ref{algo.comp}, it
+iteratively runs the following operations:

 \begin{itemize}
 \item if some load was received from the neighbors, get it;
 \item if there is some load to send to the neighbors, send it;
 \begin{itemize}
 \item if some load was received from the neighbors, get it;
 \item if there is some load to send to the neighbors, send it;


@@ -349,7 +380,35 @@ real load management.  It iteratively runs the following operations:
 \end{itemize}
 Practically, after the computation, the computing thread waits for a
 small amount of time if the iterations are looping too fast (for
 \end{itemize}
 Practically, after the computation, the computing thread waits for a
 small amount of time if the iterations are looping too fast (for

-example, when the current load is zero).
+example, when the current load is near zero).
+
+\begin{algorithm}
+  \caption{Computing thread}
+  \label{algo.comp}
+  \KwData{
+    \begin{algodata}
+      \VAR{data\_fifo} & buffer of received data messages \\
+      \VAR{real\_load} & current load \\
+    \end{algodata}}
+  \While{true}{%
+    \If{\VAR{data\_fifo} is empty and $\VAR{real\_load} = 0$}{%
+      wait until a message is pushed into \VAR{data\_fifo}\;
+    }
+    \While{\VAR{data\_fifo} is not empty}{%
+      pop a message from \VAR{data\_fifo}\;
+      get the load embedded in the message, and add it to \VAR{real\_load}\;
+    }
+    \ForEach{neighbor $n$}{%
+      \If{there is some amount of load $a$ to send to $n$}{%
+        send $a$ units of load to $n$, and subtract it from \VAR{real\_load}\;
+      }
+    }
+    \If{$\VAR{real\_load} > 0.0$}{
+      simulate some computation, whose duration is function of \VAR{real\_load}\;
+      ensure that the main loop does not iterate too fast\;
+    }
+  }
+\end{algorithm}

 
 \paragraph{Load-balancing thread} The load-balancing thread is in
 charge of running the load-balancing algorithm, and exchange the
 
 \paragraph{Load-balancing thread} The load-balancing thread is in
 charge of running the load-balancing algorithm, and exchange the


@@ -363,10 +422,35 @@ control messages.  It iteratively runs the following operations:
   iterate too fast.
 \end{itemize}
 
   iterate too fast.
 \end{itemize}
 

+\begin{algorithm}
+  \caption{Load-balancing}
+  \label{algo.lb}
+  \While{true}{%
+    \While{\VAR{ctrl\_fifo} is not empty}{%
+      pop a message from \VAR{ctrl\_fifo}\;
+      identify the sender of the message,
+      and update the current knowledge of its load\;
+    }
+    run the load-balancing algorithm to make the decision about load transfers\;
+    \ForEach{neighbor $n$}{%
+      send a control messages to $n$\;
+    }
+    ensure that the main loop does not iterate too fast\;
+  }
+\end{algorithm}
+
+\paragraph{}
+For the sake of simplicity, a few details were voluntary omitted from
+these descriptions.  For an exhaustive presentation, we refer to the
+actual code that was used for the experiments, and which is
+available at \textbf{FIXME URL}.
+
+\textbf{FIXME: ajouter des détails sur la gestion de la charge virtuelle ?}
+

 \subsection{Experimental contexts}
 \label{Contexts}
 
 \subsection{Experimental contexts}
 \label{Contexts}
 

-\textbf{FIXME once the experimentations are done!}
+\textbf{FIXME once the experimentation is done!}

 \begin{description}
 \item[platforms] homogeneous ; heterogeneous generated with the SIMULACRUM tool~\cite{QUINSON:2010:INRIA-00502839:1}
 \item[topologies]
 \begin{description}
 \item[platforms] homogeneous ; heterogeneous generated with the SIMULACRUM tool~\cite{QUINSON:2010:INRIA-00502839:1}
 \item[topologies]


@@ -421,4 +505,4 @@ Taille : 10 100 très gros
 
 % LocalWords:  Raphaël Couturier Arnaud Giersch Abderrahmane Sider Franche ij
 % LocalWords:  Bertsekas Tsitsiklis SimGrid DASUD Comté Béjaïa asynchronism ji
 
 % LocalWords:  Raphaël Couturier Arnaud Giersch Abderrahmane Sider Franche ij
 % LocalWords:  Bertsekas Tsitsiklis SimGrid DASUD Comté Béjaïa asynchronism ji

-% LocalWords:  ik isend irecv
+% LocalWords:  ik isend irecv Cortés et al chan ctrl fifo