Report of "Bug" with Switching from FSRS back to older versions

This issue means users should know that there will be an issue if a person decides to switch to FSRS, do reviews, then later swap back to an Anki version without FSRS.

Not really a bug as its obvious this issue would happen, and I shouldn’t have done it in the first place.

How to replicate:

  1. (Optional) Recall card using default anki algorithm
  2. Recall call using FSRS algorithm
  3. Revert Anki version back to verion without FSRS implementation
  4. Card will now use the FSRS D% as the Ease % directly

Do you have Card Info that shows this happening?

In #3, do you just mean – flip the FSRS switch off? After you did that, did you study (and grade) the card again?

No I dont have the card info. But I do remember it that it directly took the Ease percentage from the D%. ie. if D was 81.6%, the new ease was now 81.6%
Ie. it show would show:
Previous Recall: Ease: 81.6%
The recall prior: Ease: 250%

In 3., I mean downgrade anki version.

I did not test studying the card again.

If you didn’t study the card again, then how do you know what Ease was applied after downgrading to using the SM-2 algorithm instead?

When you’re using FSRS, Anki repurposes the “Ease” column in the Card Info to display Difficulty, but that doesn’t mean that Anki gets the ease and D figures confused. They are stored in different places and used in different formulas.

If you have Card Info showing the wrong value being applied, add that here, so someone can take a look.

Older Anki versions don’t know how to display the difficulty value correctly, but it shouldn’t cause any harm with the scheduling.

Ah, you are that discord user. I remember you posted this

Yeah, that is just a display issue, like Damien said. The card hasn’t been reviewed again under SM-2.

From a support perspective, It’s actually good that the D value is maintained for that line in the card info, because now we know which reviews were done under FSRS. There’s no overlap between the possible range of ease values and D values, so no chance of confusion.

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