1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
;;; gnosis-algorithm.el --- Spaced Repetition Algorithm for Gnosis -*- lexical-binding: t; -*-
;; Copyright (C) 2023 Thanos Apollo
;; Author: Thanos Apollo <[email protected]>
;; Keywords: extensions
;; URL: https://git.thanosapollo.org/gnosis
;; Version: 0.0.1
;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; Handles date calculation as well as ef & interval calculations.
;; This file contains the algorithm for the spaced repetition system used in Gnosis.
;; Gnosis algorithm is inspired by the SM-2 algorithm used in Anki, but has been
;; modified to fit the needs of Gnosis.
;;; Code:
(require 'cl-lib)
(require 'calendar)
(defcustom gnosis-algorithm-interval '(1 3)
"Gnosis initial interval for successful reviews.
First item: First interval,
Second item: Second interval."
:group 'gnosis
:type '(list integer))
(defcustom gnosis-algorithm-ef '(0.35 0.30 1.3)
"Gnosis easiness factor.
First item : Increase factor
Second item: Decrease factor
Third item : Starting total ef
Note: Starting total ef should not be above 3.0"
:group 'gnosis
:type '(list float))
(defcustom gnosis-algorithm-ff 0.5
"Gnosis forgetting factor.
Used to calcuate new interval for failed questions.
NOTE: Do not change this value above 1"
:group 'gnosis
:type 'float)
(defcustom gnosis-algorithm-ef-increase 0.1
"Increase ef increase value by this amount for every
`gnosis-algorithm-ef-threshold' number of successful reviews."
:group 'gnosis
:type 'float)
(defcustom gnosis-algorithm-ef-decrease 0.2
"Decrease ef decrease value by this amount for every
`gnosis-algorithm-ef-threshold' number of failed reviews."
:group 'gnosis
:type 'float)
(defcustom gnosis-algorithm-ef-threshold 3
"Threshold for updating ef increase/decrease values.
Refers to the number of consecutive successful or failed reviews."
:group 'gnosis
:type 'integer)
(defun gnosis-algorithm-replace-at-index (index new-item list)
"Replace item at INDEX with NEW-ITEM in LIST."
(cl-loop for item in list
for i from 0
collect (if (= i index) new-item item)))
(defun gnosis-algorithm-round-items (list)
"Round all items in LIST to 2 decimal places."
(cl-loop for item in list
collect (/ (round (* item 100)) 100.0)))
(defun gnosis-algorithm-date (&optional offset)
"Return the current date in a list (year month day).
Optional integer OFFSET is a number of days from the current date."
(let* ((now (decode-time))
(now (list (decoded-time-month now)
(decoded-time-day now)
(decoded-time-year now))))
(let ((date (if (zerop (or offset 0))
now
(calendar-gregorian-from-absolute
(+ offset (calendar-absolute-from-gregorian now))))))
(list (nth 2 date) (nth 0 date) (nth 1 date)))))
(defun gnosis-algorithm-date-diff (date)
"Find the difference between the current date and the given DATE.
DATE format must be given as (year month day)."
(let ((given-date (encode-time 0 0 0 (caddr date) (cadr date) (car date))))
(- (time-to-days (current-time))
(time-to-days given-date))))
(cl-defun gnosis-algorithm-next-ef (&key ef success increase decrease threshold
c-successes c-failures)
"Returns the new EF, (increase-value decrease-value total-value)
Calculate the new e-factor given existing EF and SUCCESS, either t or nil.
Next EF is calculated as follows:
Upon a successful review, increase total ef value (nth 2) by
ef-increase value (nth 0).
Upon a failed review, decrease total ef by ef-decrease value (nth 1).
For every THRESHOLD of C-SUCCESSES (consecutive successful reviews)
reviews, increase ef-increase by INCREASE.
For every THRESHOLD of C-FAILURES reviews, decrease ef-decrease value
by DECREASE."
(cl-loop for (param type) in '((ef listp) (success booleanp) (increase numberp)
(decrease numberp) (threshold numberp))
do (cl-assert (funcall type (symbol-value param)) nil
"Assertion failed: %s must be of type %s" param type))
(let ((threshold-p (= (% (max 1 (if success c-successes c-failures)) threshold) 0))
(new-ef (if success (gnosis-algorithm-replace-at-index 2 (+ (nth 2 ef) (nth 0 ef)) ef)
(gnosis-algorithm-replace-at-index 2 (max 1.3 (- (nth 2 ef) (nth 1 ef))) ef))))
(cond ((and success threshold-p)
(setf new-ef (gnosis-algorithm-replace-at-index 0 (+ (nth 0 ef) increase) new-ef)))
((and (not success) threshold-p
(setf new-ef (gnosis-algorithm-replace-at-index 1 (+ (nth 1 ef) decrease) new-ef)))))
(gnosis-algorithm-round-items new-ef)))
(cl-defun gnosis-algorithm-next-interval (&key last-interval ef success successful-reviews
failure-factor initial-interval)
"Calculate next interval."
(cl-assert (< gnosis-algorithm-ff 1) "Value of `gnosis-algorithm-ff' must be lower than 1")
;; This should only occur in testing env or when the user has made breaking changes.
(cl-assert (> (nth 2 ef) 1) "Total ef value must be above 1")
(let* ((ef (nth 2 gnosis-algorithm-ef))
(interval (cond ((and (= successful-reviews 0) success)
(car initial-interval))
((and (= successful-reviews 1) success)
(cadr initial-interval))
(t (if success
(* ef last-interval)
(* failure-factor last-interval))))))
(gnosis-algorithm-date (round interval))))
(provide 'gnosis-algorithm)
;;; gnosis-algorithm.el ends here
|
