fsrs4anki

A modern Anki custom scheduling based on Free Spaced Repetition Scheduler algorithm

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Quick Overview

FSRS4Anki is an implementation of the Free Spaced Repetition Scheduler (FSRS) algorithm for Anki, a popular flashcard application. It aims to improve the scheduling of flashcards for more efficient learning and memory retention by using a machine learning model to predict the optimal review intervals.

Pros

Implements an advanced spaced repetition algorithm (FSRS) for potentially more effective learning
Integrates seamlessly with Anki, a widely-used flashcard application
Provides customizable parameters for fine-tuning the scheduling behavior
Includes tools for analyzing and visualizing review data

Cons

Requires some technical knowledge to set up and configure
May have a learning curve for users accustomed to Anki's default scheduler
Potential for over-optimization, which could lead to less natural learning patterns
Limited compatibility with older versions of Anki

Code Examples

# Example 1: Creating an FSRS object
from fsrs import FSRS, Card, ReviewLog

fsrs = FSRS()
card = Card(due=0)

This code initializes an FSRS object and creates a new card with a due date of 0.

# Example 2: Simulating a review
now = 1600000000
result = fsrs.repeat(card, now)
new_card, review_log = result.card, result.review_log

This example simulates a card review at a specific timestamp and returns the updated card state and review log.

# Example 3: Customizing FSRS parameters
custom_fsrs = FSRS(
    request_retention=0.9,
    maximum_interval=36500,
    w=[0.4, 0.6, 2.4, 5.8, 4.93, 0.94, 0.86, 0.01, 1.49, 0.14, 0.94, 2.18, 0.05, 0.34, 1.26, 0.29, 2.61]
)

This code creates an FSRS object with custom parameters, including desired retention rate, maximum interval, and weight values for the algorithm.

Getting Started

To use FSRS4Anki:

Install Anki 2.1.45+ and the FSRS4Anki add-on from the AnkiWeb page.
In Anki, go to Tools > Add-ons > FSRS4Anki > Config to customize settings.
Create or import a deck and start reviewing cards.
(Optional) Use the provided analysis tools to visualize your review data:

from fsrs4anki_analyzer import FSRSAnalyzer

analyzer = FSRSAnalyzer()
analyzer.plot_retention_curve()
analyzer.plot_difficulty_distribution()

These steps will get you started with using FSRS4Anki in your Anki studies.

Competitor Comparisons

Anki-Android

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Pros of Anki-Android

Full-featured mobile app for Anki, providing a complete spaced repetition experience on Android devices
Syncs with AnkiWeb, allowing seamless integration with the desktop version of Anki
Large user base and active community support

Cons of Anki-Android

Limited customization options for the spaced repetition algorithm
Potentially overwhelming interface for new users due to the wide range of features

Code Comparison

FSRS4Anki (Python):

def init_model(self):
    self.w = [1, 1, 5, -0.5, -0.5, 0.2, 1.4, -0.12, 0.8, 2, -0.2, 0.2, 1]
    self.theta = [0.4, 0.6, 2.4, 5, 0.5, 1.0, 1.2, 0.8, 2.0, 0.3, 1.5]

Anki-Android (Java):

public class Scheduler {
    private static final int LEARNING_STEPS = 3;
    private static final int GRADUATING_INTERVAL = 1;
    private static final int EASY_INTERVAL = 4;
    private static final int INITIAL_EASE = 2500;
}

The code snippets show different approaches to implementing spaced repetition algorithms. FSRS4Anki uses a more complex model with weights and parameters, while Anki-Android employs a simpler scheduling system with fixed intervals and ease factors.

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README

FSRS4Anki

â¨ A modern spaced-repetition scheduler for Anki based on the Free Spaced Repetition Scheduler algorithm â¨

611Study.ICU

Hi, I'm Jarrett Ye, the creator of FSRS. FSRS is a highly efficient spaced repetition algorithm used by many people worldwide, saving considerable time. It applies cognitive science and educational technology to help students learn more effectively.

However, most Chinese high school students are still forced to study "611" - from 6 AM to 11 PM, six days a week. Tragically, many students have committed suicide or developed serious mental health issues.

The 611Study.ICU project aims to stop this abusive study model and protect students' lives and health.

As a former Chinese student, I experienced overtime study and sleep deprivation during high school. Anki saved my life. I want to use this algorithm to save more lives, but most Chinese high schools still prevent students from using it.

I hope this project can raise awareness and help more students.

Introduction
How to Get Started?
Add-on Compatibility
Contribute
- Contributors
Developer Resources
Stargazers Over Time

Introduction

FSRS4Anki consists of two main parts: the scheduler and the optimizer.

The scheduler replaces Anki's built-in scheduler and schedules the cards according to the FSRS algorithm.
The optimizer uses machine learning to learn your memory patterns and finds parameters that best fit your review history. For details about the working of the optimizer, please read the mechanism of optimization.

For details about the FSRS algorithm, please read the algorithm. If you are interested, you can also read my papers:

A Stochastic Shortest Path Algorithm for Optimizing Spaced Repetition Scheduling (free access), and
Optimizing Spaced Repetition Schedule by Capturing the Dynamics of Memory (Google Scholar).

FSRS4Anki Helper is an Anki add-on that complements the FSRS4Anki Scheduler. You can read about it here: https://github.com/open-spaced-repetition/fsrs4anki-helper

How to Get Started?

If you are using Anki v23.10 or newer, refer to this tutorial.

If you are using an older version of Anki, refer to this tutorial.

Note that setting up FSRS is much easier in Anki v23.10 or newer.

Add-on Compatibility

Some add-ons can cause conflicts with FSRS. As a general rule of thumb, if an add-on affects a card's intervals, it shouldn't be used with FSRS.

Add-on	Compatible?	Comment
Review Heatmap	Yes :white_check_mark:	Doesn't affect anything FSRS-related.
Advanced Browser	Yes :white_check_mark:	Please use the latest version.
Advanced Review Bottom Bar	Yes :white_check_mark:	Please use the latest version.
The KING of Button Add-ons	Yes :white_check_mark:	Please use the latest version.
Pass/Fail	Yes :white_check_mark:	`Pass` is the equivalent of `Good`, `Fail` is the equivalent of `Again.`
AJT Card Management	Yes :white_check_mark:	Compatible with Anki 23.12 and newer.
Incremental Reading v4.11.3 (unofficial clone)	Unsure :question:	If you are using the standalone version of FSRS, it shows the interval given by Anki's built-in scheduler, not the custom scheduler. This add-on is technically compatible with built-in FSRS, but FSRS was not designed for incremental reading, and FSRS settings do not apply to IR cards because they work in a different way compared to other card types.
Delay siblings	No :x:	Delay siblings will modify the intervals given by FSRS. However, the FSRS4Anki Helper add-on has a similar feature that works better with FSRS. Please use the FSRS4Anki Helper add-on instead.
Auto Ease Factor	No :x:	The Ease Factor is no longer relevant when FSRS is enabled, therefore you won't benefit from using this add-on.
autoLapseNewInterval	No :x:	The `New Interval` setting is no longer relevant when FSRS is enabled, therefore you won't benefit from using this add-on.
Straight Reward	No :x:	The Ease Factor is no longer relevant when FSRS is enabled, therefore you won't benefit from using this add-on.

Let me know via issues if you want me to check compatibility between FSRS and some add-on.

Contribute

You can contribute to FSRS4Anki by beta testing, submitting code, or sharing your data. If you want to share your data with me, please fill out this form: https://forms.gle/KaojsBbhMCytaA7h8

Contributors

_Expertium
â ï¸ ð ð£ ð¤ ð

_user1823
â ï¸ ð ð£ ð¤ ð

_{Christos Longros}
ð£ ð

Developer Resources

If you're a developer considering using the FSRS algorithm in your own projects, we've curated some valuable resources for you. Check out the Awesome FSRS repository, where you'll find:

FSRS implementations in various programming languages
Related papers and research
Example applications using FSRS
Other algorithms and resources related to spaced repetition systems

This carefully curated list will help you better understand FSRS and choose the right implementation for your project. We encourage you to explore these resources and consider contributing to the FSRS ecosystem.

Stargazers Over Time

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fsrs4anki

Top Related Projects

Anki-Android

Quick Overview

Pros

Cons

Code Examples

Getting Started

Competitor Comparisons

Anki-Android

Pros of Anki-Android

Cons of Anki-Android

Code Comparison

Convert designs to code with AI

README

FSRS4Anki

611Study.ICU

Table of contents

Introduction

How to Get Started?

Add-on Compatibility

Contribute

Contributors

Developer Resources

Stargazers Over Time

Top Related Projects

Anki-Android

Convert designs to code with AI