Update README.md to add score formula

README.md

@@ -3,7 +3,14 @@
 Annex to the UNIGE HPC cluster AIMP 2019 related to the PL12146.
 You will find the details of every benchmarks to be executed below.
 
-The weighting of each benchmark in the composite average score is indicated between square brackets:
+To compute a composite global score, we will:
+
+ 1. Normalize each by the results we obtained on a reference machine
+ 2. Multiply the result by 100
+ 3. Compute the weighted average mean
+
+The weighting of each benchmark in the composite average score is indicated
+between square brackets:
 
 Synthetic benchmarks:
 
@@ -16,3 +23,4 @@ User application benchmarks:
  * [Palabos](Palabos/README.md) [14%]
  * [CP2K](CP2K/README.md) [14%]
  * [TensorFlow](TensorFlow/README.md) [14%]
+