\section{Experimental results}
\label{sec.expe}
+While in~\cite{mpi-energy2} the energy model and the scaling factors selection algorithm were applied to a heterogeneous cluster and evaluated over the SimGrid simulator~\cite{SimGrid.org},
+in this paper real experiments were conducted over the grid'5000 platform.
\subsection{Grid'5000 architature and power consumption}
\label{sec.grid5000}
-The grid'5000 is a large-scale testbed found in France \cite{grid5000}.
-The grid infrastructure consist of ten sites distributed over all France
-metropolitan regions. Each site in the grid'5000 composed from number of heterogeneous
-computing clusters, while each cluster includes a collection of homogeneous nodes.
-In general, the grid'5000 had one thousand of heterogeneous nodes and eight thousand of cores.
-All the sites are connected together via special long distance network called RENATER,
-which is the French National Telecommunication Network for Technology. Whereas inside each site
-the clusters and their nodes are connected throw high speed local area networks.
-There are different types of local networks used such as Ethernet and Infiniband netwoks,
-which allowed different gigabits bandwidth and latencies. On the other hand, the nodes inside each cluster
-are homogeneous, while they are different from the nodes of the other clusters. Therefore, there are
-a wide diversity of processors in grid'5000, that mainly had different processors families
-such as Intel Xeon and AMD Opteron families.
-
-In this paper we are interested to run NAS parallel v3.3 \cite{NAS.Parallel.Benchmarks} over grid'5000.
+Grid'5000~\cite{grid5000} is a large-scale testbed that consists of ten sites distributed over all metropolitan France and Luxembourg. All the sites are connected together via a special long distance network called RENATER,
+which is the French National Telecommunication Network for Technology.
+Each site of the grid is composed of few heterogeneous
+computing clusters and each cluster contains many homogeneous nodes. In total,
+ grid'5000 has about one thousand heterogeneous nodes and eight thousand cores. In each site,
+the clusters and their nodes are connected via high speed local area networks.
+Two types of local networks are used, Ethernet or Infiniband networks which have different characteristics in terms of bandwidth and latency.
+
+Since grid'5000 is dedicated for testing, contrary to production grids it allows a user to deploy its own customized operating system on all the booked nodes. The user could have root rights and thus apply DVFS operations while executing a distributed application.
+
+
+
+we are interested to run NAS parallel v3.3 \cite{NAS.Parallel.Benchmarks} over grid'5000.
We are used seven benchmarks, CG, MG, EP, LU, BT, SP and FT. These benchmarks used seven different types of classes.
These classes are S, W, A, B, C, D, E, where S represents the smaller problem size that used by benchmark and
E is represents the biggest class. In this work, the class D is used for all benchmarks in all the experiments that will
