Improved saturation criterion
Improved saturation criterion

- Find plateau using a running standard deviation
- Compute slope on that plateau


Former-commit-id: a8bda9c3f7fe2b4dc959f79651e19c58c2fe18b2
DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG