User:Vikram Atreya/GSoC21/Project

Implementing UNDO command

Community Bonding

• Set up the blog and wiki
• Decide on which approach to implement UNDO

Development Plan

• Week 1: Decide architecture and create the required files to have an undo cmd
  • Add files to libged, make changes in Cmake files and decide on space/location to store the temporary data being generated. Write documentation on how the undo command is going to be implemented and how it will work.
• Week 2: Start implementing the UNDO logic
  • Check for different commands like kill, make and other basic commands for proper compatibility with the UNDO command.
• Week 3: Continue the implementation
  • Start working and testing for complicated commands like dbconcat which deal with overwriting, creating new objects and deleting multiple objects. In the partial + events method this might take more time as splitting commands into events is a big task.
• Week 4: Get a basic review and start testing
  • Take inputs from my mentor on current progress and how I could improve the code. Write tests for various cases and check robustness.
• Week 5: Continue testing and optimizing code
• Week 6: Work on further optimizations / Account for unforeseen delays
  • I will keep this week as a buffer.
• Week 7: Optimizations to UNDO
  • Depending on the method chosen, work on improving the time/space complexity of the implementation.
• Week 8: Document work and issues faced
• Week 9: Prepare for final evaluations

Design ideas

• Facilitate 10-15 undos from the latest state
• Initially no redo command and later states are deleted once undo is used
• Works only on objects and not on other data stored
• Plain undo with no flags does just 1 undo
• ``` -n X``` flag does multiple undos, where X is no of undos to be done

Implementation ideas

• Full checkpoint is stored before 15 commands.
• Form an array with values as names of all non-hidden objects, search for backups in hidden objects (backup should have a version just previous to the no of undos requested). After iterating through all backup objects if we do not find a backup, ,which should ideally be found in the full checkpoint even if it was not backed up later, we killthat object.
• Undo can also be considered to be a normal command and full checpoint can be created before undoing, so that redo will be done with an undo.