X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/loba-papers.git/blobdiff_plain/c8b7a837b49a20dcbce655c5c891aea3f25542f5..f13866736c2d1dda2bc227e4a05626ea5535e7d6:/supercomp11/supercomp11.tex

diff --git a/supercomp11/supercomp11.tex b/supercomp11/supercomp11.tex
index 49477d7..1faf1b0 100644
--- a/supercomp11/supercomp11.tex
+++ b/supercomp11/supercomp11.tex
@@ -29,12 +29,12 @@
 }
 
 \institute{R. Couturier \and A. Giersch \at
-              LIFC, University of Franche-ComtÃ©, Belfort, France \\
+              FEMTO-ST, University of Franche-ComtÃ©, Belfort, France \\
               % Tel.: +123-45-678910\\
               % Fax: +123-45-678910\\
               \email{%
-                raphael.couturier@univ-fcomte.fr,
-                arnaud.giersch@univ-fcomte.fr}
+                raphael.couturier@femto-st.fr,
+                arnaud.giersch@femto-st.fr}
 }
 
 \maketitle
@@ -489,8 +489,19 @@ To summarize the different load balancing strategies, we have:
 %
 This gives us as many as $4\times 2\times 2 = 16$ different strategies.
 
+\paragraph{End of the simulation}
 
-\paragraph{Configurations}
+The simulations were run until the load was nearly balanced among the
+participating nodes.  More precisely the simulation stops when each node holds
+an amount of load at less than 1\% of the load average, during an arbitrary
+number of computing iterations (2000 in our case).
+
+Note that this convergence detection was implemented in a centralized manner.
+This is easy to do within the simulator, but it's obviously not realistic.  In a
+real application we would have chosen a decentralized convergence detection
+algorithm, like the one described in \cite{10.1109/TPDS.2005.2}.
+
+\paragraph{Platforms}
 
 In order to show the behavior of the different strategies in different
 settings, we simulated the executions on two sorts of platforms.  These two
@@ -511,11 +522,15 @@ bandwidth was fixed to 2.25~GB/s, with a latency of 500~$\mu$s.
 Then we derived each sort of platform with four different number of computing
 nodes: 16, 64, 256, and 1024 nodes.
 
+\paragraph{Configurations}
+
 The distributed processes of the application were then logically organized along
 three possible topologies: a line, a torus or an hypercube.  We ran tests where
 the total load was initially on an only node (at one end for the line topology),
-and other tests where the load was initially randomly distributed across all
-the participating nodes.
+and other tests where the load was initially randomly distributed across all the
+participating nodes.  The total amount of load was fixed to a number of load
+units equal to 1000 times the number of node.  The average load is then of 1000
+load units.
 
 For each of the preceding configuration, we finally had to choose the
 computation and communication costs of a load unit.  We chose them, such as to
@@ -552,13 +567,45 @@ time.
 
 \paragraph{Metrics}
 
+In order to evaluate and compare the different load balancing strategies we had
+to define several metrics.  Our goal, when choosing these metrics, was to have
+something tending to a constant value, i.e. to have a measure which is not
+changing anymore once the convergence state is reached.  Moreover, we wanted to
+have some normalized value, in order to be able to compare them across different
+settings.
+
+With these constraints in mind, we defined the following metrics:
+%
 \begin{description}
-\item[\textbf{average idle time}]
-\item[\textbf{average convergence date}]
-\item[\textbf{maximum convergence date}]
-\item[\textbf{data transfer amount}] relative to the total data amount
+\item[\textbf{average idle time:}] that's the total time spent, when the nodes
+  don't hold any share of load, and thus have nothing to compute.  This total
+  time is divided by the number of participating nodes, such as to have a number
+  that can be compared between simulations of different sizes.
+
+  This metric is expected to give an idea of the ability of the strategy to
+  diffuse the load quickly.  A smaller value is better.
+
+\item[\textbf{average convergence date:}] that's the average of the dates when
+  all nodes reached the convergence state.  The dates are measured as a number
+  of (simulated) seconds since the beginning of the simulation.
+
+\item[\textbf{maximum convergence date:}] that's the date when the last node
+  reached the convergence state.
+
+  These two dates give an idea of the time needed by the strategy to reach the
+  equilibrium state.  A smaller value is better.
+
+\item[\textbf{data transfer amount:}] that's the sum of the amount of all data
+  transfers during the simulation.  This sum is then normalized by dividing it
+  by the total amount of data present in the system.
+
+  This metric is expected to give an idea of the efficiency of the strategy in
+  terms of data movements, i.e. its ability to reach the equilibrium with fewer
+  transfers.  Again, a smaller value is better.
+
 \end{description}
 
+
 \subsection{Validation of our approaches}
 \label{Results}
 
