The SuperMemo-2 (SM-2) algorithm, created by Polish researcher Piotr Woźniak in the late 1980s, remains the gold standard for spaced repetition scheduling. It powers major flashcard systems like Anki, and now forms the core engine of ChunkMaster.
The Math of Scheduling
The scheduler determines the interval (in days) until the next review based on the number of consecutive successful repetitions (n) and an Ease Factor (EF). The EF defaults to 2.5 and adjusts based on user feedback rating scores (0-5 scale):
- Interval 1 (First Repetition): Scheduled for 1 day.
- Interval 2 (Second Repetition): Scheduled for 6 days.
- Interval n (n > 2):
Interval(n) = Interval(n-1) * EaseFactor
Feedback Adjustments
After viewing the card, your grade determines how the Ease Factor shifts:
- Again (Grade 0): forgotten. Repetitions counter resets to 0, EF drops by 0.2, and it is rescheduled immediately.
- Hard (Grade 3): EF drops by 0.15, next interval scales slightly.
- Good (Grade 4): EF stays stable, next interval multiplied by EF.
- Easy (Grade 5): EF increases by 0.15, next interval gets a 30% bonus.
By adjusting these coefficients dynamically, ChunkMaster adjusts to your personal memory speed, ensuring maximum retention with minimal reviews.