added README

Author: pancetta

examples/fault_tolerance/README.md

@@ -0,0 +1,19 @@
+Emulating node failure with pySDC
+=================================
+
+This example has different scripts to emulate node failures in PFASST and evaluate the outcome of different recovery 
+strategies. This example folder has all the scripts to produce the figures/results from the corresponding paper, namely:
+
+* hard_faults_test.py: generate data to check iteration counts for node failures at different steps and iterations, 
+can do HEAT and ADVECTION example and all the different strategies described in the paper. 
+The script postproc_hard_faults_test.py produces the corresponding heatmaps.
+* hard_faults_detail.py: generate data to check residuals for a node failure at a specified step and iteration, can do
+HEAT and ADVECTION example and all the different strategies described in the paper. 
+The script postproc_hard_faults_detail.py produces the corresponding plots.
+* grayscott_example.py: runs the 1D gray-scott example using FEniCS, emulates random node failures and dumps the residuals. 
+The script postproc_grayscott.py produces the corresponding plots, the script animate_convergence.py gives some nice movies 
+(very specific, not suitable for general purpose).
+ 
+Warning: the are many global variables and hard-implemented numbers floating around in the code 
+(e.g. random node failures for the gray-scott example are not allowed to occure beyond iteration 6, 
+since the original example only takes 6 iterations). Also, to run the gray-scott example, FEniCS must be installed.