[bug#73220] [PATCH] ui: Add more nuance to relevance scoring.

[aurtzy <aurtzy@gmail.com>]

Fixes <https://issues.guix.gnu.org/70689>.

* guix/ui.scm (char-set:word-border): New variable.
(relevance): Update docstring.
[whole-word-score, exact-match-score]: New variables.
[score]: Score whole words such that matching a whole word will always put an
object higher than another if the other does not match any whole words.  Exact
matches are given similar treatment.  Score matches slightly higher than the
baseline if they have one word boundary, with the assumption that they are
more likely to be part of compound words rather than simply substrings.  Only
count a maximum of one scored match per field to limit putting too much weight
on terms that happen to be very common.
[score][string-ref-border?]: New procedure.

Change-Id: I8e3d7a20bf296485355d1c191fe3fee5ef6490c8
---

Hello!

This is an attempt to improve guix's search functionality for cases like the
linked issue.

Elaborating on some parts of my implementation:

I opted to switch to counting a maximum of one match per field, which helps
with cases where a common subword matches /many/ times in packages with longer
descriptions, pushing more relevant packages down.  In multi-term searches,
the unique terms - which are naturally rarer - also contribute to a larger
percentage of the score as a result of these changes.

Having matches with only one word boundary be scored as 2 instead of 1 was
done with the reasoning that a term is more likely to be part of a compound
word name (and thus more relevant) if it is a prefix or suffix; for example,
"gl" in OpenGL, "borg" in borgmatic, and "tor" in torbrowser.

In an effort to minimize regressions in scoring, I've compiled a set of test
cases and their expected results, which - if useful - might also be usable in
future work:

| Keyword(s) with poor  | Expectations                                  |
| results before        |                                               |
|-----------------------+-----------------------------------------------|
| dig                   | ~bind~ near top.                              |
| rsh                   | ~inetutils~ near top.                         |
| c                     | C language related.                           |
| c compiler            | Compiler-related C stuff.                     |
| r                     | R language related.                           |
| tor                   | Tor related; ~torbrowser~ somewhere near top. |
| gcc                   | ~gcc-toolchain~ near top.                     |
|-----------------------+-----------------------------------------------|
| Keyword(s) with mixed |                                               |
| results before        |                                               |
|-----------------------+-----------------------------------------------|
| gl                    | GL related.                                   |
| sh                    | Shell-related.                                |
|-----------------------+-----------------------------------------------|
| Keywords(s) with good |                                               |
| results before        |                                               |
|-----------------------+-----------------------------------------------|
| gcc toolchain         | ~gcc-toolchain~ near top.                     |
| python                | ~python~ at top.                              |
| python language       | ~python~ at top.                              |
| python minimal        | ~python{,2}-minimal~ and friends near top.    |
| sync files            | File synchronization related.                 |
| sdl2                  | ~sdl2~ at top.                                |

However, some of these cases might be a bit too abstract, so I'm not sure how
sufficient this testing is.  Note that I only did minimal testing with =guix
system search= and =guix home search= which - while seemingly fine - could be
more rigorous (am I forgetting any other commands?).

Going over the results of these changes on the test cases:

There were notable improvements searching:
- =rsh=: ~inetutils~ now shows up at the top when searching =rsh=, with
  another relevant (but previously buried) ~emacs-tramp~ at second place.
- =c=: Searches for =c= return results related to the language now, whereas
  before it was a lot of unrelated packages that simply had the most =c=
  characters.
- =dig=: While not the first result, ~bind~ is now displayed as tied for 3rd
  in relevance score, showing up within 10 packages.
- =r=: Previously in a similar situation as C.  Now ~r~ shows up at the top,
  with other R-related packages under it.
- =gl=: The =gl= test case's results are slightly improved.  Before, there
  were some non-relevant packages with the =gl= substring near the top, which
  is no longer the case.
- =sh=: As a common subword, searching =sh= led to a mix of relevant and less
  relevant results at the top.  A good majority are now shell-related.
- =tor=: ~tor~ shows up on the top in both cases, but before with lots of
  non-relevant packages under it; the previously buried ~torbrowser~ now
  accompanies other more relevant results near the top.
- =gcc=: ~gcc-toolchain~ is now a top result, compared to ~gccgo~ at the top
  before (and even ~gdc-toolchain~ also being higher; upstream name being
  "gcc" seems to have caused that).


There are slight regressions with searching:
- =sync files=: The new algorithm has a few less relevant results at the top
  compared to before, but otherwise seems like a shuffling of the old results.
- =sdl2=: ~sdl2~'s top rank is overtaken by two libraries.


If I didn't mention a test case from the table, it's probably because results
were at least consistent or better (and I think I've written too much to read
already).

Closing this message on an unrelated note for future work: I stumbled on an
interesting idea while looking for test cases which suggested reducing the
score of a programming library when its language is not included in search
terms.  It's out of scope for the current issue, but I thought I'd mention it
anyways for potential further improvements.

Cheers,

aurtzy

 guix/ui.scm | 54 ++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 45 insertions(+), 9 deletions(-)

diff --git a/guix/ui.scm b/guix/ui.scm
index 966f0611f6..420f1f7501 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -19,6 +19,7 @@
 ;;; Copyright © 2018 Steve Sprang <scs@stevesprang.com>
 ;;; Copyright © 2022 Taiju HIGASHI <higashi@taiju.info>
 ;;; Copyright © 2022 Liliana Marie Prikler <liliana.prikler@gmail.com>
+;;; Copyright © 2024 aurtzy <aurtzy@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -1678,22 +1679,57 @@ (define* (package->recutils p port #:optional (width (terminal-columns))
 ;;; Searching.
 ;;;
 
+(define char-set:word-border (char-set-union char-set:digit
+                                             char-set:punctuation
+                                             char-set:symbol
+                                             char-set:whitespace))
+
 (define (relevance obj regexps metrics)
-  "Compute a \"relevance score\" for OBJ as a function of its number of
-matches of REGEXPS and accordingly to METRICS.  METRICS is list of
-field/weight pairs, where FIELD is a procedure that returns a string or list
-of strings describing OBJ, and WEIGHT is a positive integer denoting the
-weight of this field in the final score.
+  "Compute a \"relevance score\" for OBJ as a function of its matches of REGEXPS and
+accordingly to METRICS.  METRICS is list of field/weight pairs, where FIELD is a
+procedure that returns a string or list of strings describing OBJ, and WEIGHT is a
+positive integer denoting the weight of this field in the final score.
 
 A score of zero means that OBJ does not match any of REGEXPS.  The higher the
 score, the more relevant OBJ is to REGEXPS."
+  ;; Ensure that objects with whole word matches always score greater than (or equal
+  ;; to) objects that only match substrings.
+  (define whole-word-score (apply + (map (match-lambda
+                                           ((_ . weight) weight))
+                                         metrics)))
+  (define exact-match-score (* whole-word-score 2))
+
   (define (score regexp str)
+    (define (string-ref-border? k)
+      (if (<= 0 k (1- (string-length str)))
+          (char-set-contains? char-set:word-border (string-ref str k))
+          #t))
+
     (fold-matches regexp str 0
                   (lambda (m score)
-                    (+ score
-                       (if (string=? (match:substring m) str)
-                           5             ;exact match
-                           1)))))
+                    (cond
+                     ((string=? (match:substring m) str)
+                      exact-match-score)
+                     ((>= score whole-word-score)
+                      ;; No need to compute further if score is already max
+                      ;; possible score
+                      score)
+                     (else
+                      (let ((start-border?
+                             (string-ref-border? (1- (match:start m))))
+                            (end-border?
+                             (string-ref-border? (match:end m))))
+                        (max score
+                             (cond
+                              ((and start-border? end-border?)
+                               whole-word-score)
+                              ((or start-border? end-border?)
+                               ;; If the match only has one border, it could still be
+                               ;; part of a compound word, and thus be more likely to
+                               ;; be relevant than if it was just a substring.
+                               2)
+                              (else
+                               1)))))))))
 
   (define (regexp->score regexp)
     (let ((score-regexp (lambda (str) (score regexp str))))

base-commit: b6d5a7f5836739dab884b49a64ca354794dd845f
-- 
2.45.2