drafting a README.md file (first sketch, some parts yet to be updated)

- the zoo_sizes are not automatically recognized by the tool

README.md

+Platform Calibration (for SimGrid)
+==================================
+
+This project gathers all efforts regarding platform calibration for HPC experiments with SimGrid's SMPI.
+
+Calibration
+-----------
+
+The `calibrate` binary is an MPI application that introduces a bunch
+of MPI experiments. The goal is to profile the amount of time taken to
+execute some MPI operations in a real environment. The timings for
+such operations are obtained using the most precise clock available in
+the local node where the binary is executed. All measurements, along
+with their corresponding parameters such as message size, are dumped
+to the standard output. In a second stage, after the experiment has
+finished, an R script takes as input those measurements and a break
+points textual file informing the message sizes where the MPI protocol
+changes. As output, the R script generates the values that need to be
+included to the corresponding platform file, in order to obtain a
+faithful simulation.
+
+#### The Profiled Operations
+
+* **Blocking Receive** (R): time spent inside the _MPI_Recv_
+    function. During the benchmark initialization, through a ping-pong
+    operation, the program measures how much time the sender must
+    sleep between two benchmark procedures. Such sleep time is to be
+    sure the message that has been sent has arrived in the receiver
+    side.  After that, for a number of replications, the program
+    measures how long it took to execute the blocking receive
+    (assuming the message has already available). To guarantee all
+    replications are finished correctly, at the end, a message is sent
+    to the receiver side.
+
+* **Asynchronous Send** (AS): time spent inside the _MPI_Isend_
+    asynchronous operation. This measurement captures the time spent
+    in the buffering data and sending it to the network card. For a
+    number of replications, the program measures how long it took to
+    execute this operation when changing the message size.
+
+* **Ping-Pong** (PP): time spent to execute a sequence of a _MPI_Send_
+    followed by a _MPI_Recv_, representing together a ping pong
+    operation. The time spent in each of these two operations (send
+    and receive) is registered separately. The time spent for the
+    whole synchronous ping-pong can be obtained by summing these two
+    durations.
+
+* **Other operations** (OT): The network-unrelated functions
+    _MPI_Test_, _MPI_Iprobe_ and _MPI_Wtime_ are also profiled during
+    calibration since their CPU timings are neces
+
+#### Network Modeling
+
+The R and AS measurements (see above) represents the software overhead
+of the receive and send operations. Since the R is measured when the
+message is already available to be actually received, it is assumed
+that its duration consists exclusively in the message handling. The
+same is verified for the asynchronous send. Since the operation
+returns to the caller as soon as everything has been setup for the
+actual message transmission, we consider that it contains only the
+software overhead related to sending a message. Therefore, these two
+operations account for the software overhead, unrelated to network
+modeling itself. The network latency and bandwidth are calculated
+using the results of the PP measurements. Since the PP operation uses
+_MPI_Send_, we can check coherence of its behavior against the AS
+measurements (_MPI_Isend_).
+
+#### The Message Sizes and Variability Check
+
+We use a 10 runs of each function, each with n different sizes.  The
+sizes are taken from the file zoo_sizes.  This set was generated in
+order to provide a comprehensive set of sizes, with a good repartition
+for all magnitudes.  We can set the maximum limit for the sizes with
+-s (as sizes go up to 1GB in zoo).
+
+Saturation
+----------
+
 Forthcoming.