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https://github.com/ig3/anki-patch-nextrevivl

Anki add-on to patch the V2 schedulre _nextRevIvl function
https://github.com/ig3/anki-patch-nextrevivl

Last synced: 14 days ago
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Anki add-on to patch the V2 schedulre _nextRevIvl function

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# anki-patch-nextrevivl



Fix/improve the calculation of next review interval in the V2 scheduler,

for Good and Easy cards.



## Installation



* Download patch-nextrevivl.ankiaddon

* Start Anki and open Tools -> Add-ons

* Drag the downloaded .ankiaddon file onto the add-ons list

* Restart Anki



## Changes



This add-on monkey patches _nextRevIvl in the V2 scheduler to change the

'current interval' parameter to _constrainedIvl to be the current interval,

for both Good and Easy. By default, for Good it is the new Hard interval

and for Easy it is the new Good interval.



With this change, the next interval for a review card is at least 1 day

longer than the current interval for all cases except Hard with Hard

Interval less than 1, in which case the minimum interval is 1 day. This

changes the interval for Good and Easy but the interval for Hard is

unchanged.



This fixes a fault with Good when Hard Interval is 1 or more, in which case

the new interval was at least 2 days greater than the current interval. At

larger intervals the difference is insignificant, but at shorter intervals

with a low card factor, this leads to intervals increasing in steps of two

days, which is quite noticable in the stats graph of intervals, and may be

too much for a just learned card.



This fixes a fault with Good when Hard Interval is less than 1, with a low

card factor and low current interval, in which case the interval becomes

stuck at 2 days. With the default scheduler, the only way out of this is to

select Easy until the interval and card factor increase sufficiently that

the next interval for Good is more than 1 day longer than the current

interval.



## Motivation



By default, Hard Interval is greater than 1 and the interval for Good

increases by at least 2 days. At short intervals (e.g. 1 or 2 days) the

increase really should be only 1 day. My memory is poor and the jump from 1

day (for a just learned card) to 3 days was too much.



More significant and the immediate motivation for me making this add-on is

when I changed Hard Interval to 90% so that the interval would gradually

decrease for persistently Hard cards. With this change, I ended up

accumulating cards at interval of 2 days. With interval 2 days, the new

interval for Good was also 2 days - no progress. The only way to progress

was Easy.



These problems arise because in the default scheduler, the minimum new

interval for Good is one day more than the new interval for Hard (i.e. the

new interval for Hard is calculated and this + 1 day is the minimum new

interval for Good. The minimum new interval for Hard is 1 day more than the

current interval if Hard Interval is set to 1 or more. If Hard Interval is

less than 1, then the minimum interval for Hard is 1 day. In this latter

case, the minimum interval for Good is 2 days and with a low card factor

(minimum is 130%) Good will not increase the interval from 2 days to 3

days, so it remains stuck at 2 days.



For me, this allows me to have Hard Interval a little less than 1 (I like

about 90%, so that I see cards that are persistently Hard at progressively

shorter intervals, rather than longer intervals). For decks with Hard

Interval greater than 1 (e.g. default configuration), then the increments

in interval are, initially, a little more gradual.



Alternatives to this are: set Hard Interval to 1 or more and configure

learning steps out to several days, so that increments of review intervals

of 2 days are reasonable; Set Hard Interval less than 1 and use the Easy

button to increase the interval when it is low.