Update README.md

Author: panchoop

README.md

@@ -130,5 +130,7 @@ The code is heavily sub-optimized. Therefore expect long execution times.
 See table 1 in paper.
 
 #### FAQ:
+- When running the algorithm, nearing convergence the energy is not monotonously decreasing! 
+**ans** Try setting the tolerance value to something higher. There are rounding issues with rounding errors, see [this issue](https://github.com/panchoop/DGCG_algorithm/issues/13#issue-774344239)