| Message ID | 20210711115638.30207-1-mail@cbaines.net |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [bug#49522] weather: Don't look for exported package replacements twice. | expand |
| Context | Check | Description |
|---|---|---|
| cbaines/comparison | success | View comparision |
| cbaines/git branch | success | View Git branch |
| cbaines/applying patch | success | View Laminar job |
| cbaines/issue | success | View issue |
Hi! Christopher Baines <mail@cbaines.net> skribis: > There could be performance issues with member here, but only if there are lots > of replacements. > > * guix/scripts/weather.scm (all-packages): Return all exported packages, plus > non exported replacements, rather than including exported replacements twice. [...] > + "Return the list of packages we are going to query." > + (let* ((packages > + (fold-packages (lambda (package result) > + (cons package result)) > + '() > + > + ;; Dismiss deprecated packages but keep hidden packages. > + #:select? (negate package-superseded))) > + (non-exported-replacement-packages > + (fold-packages (lambda (package result) > + (let ((replacement (package-replacement package))) > + (if (and replacement > + ;; Avoid double couting replacements > + ;; that are themselves exported > + (not (member replacement packages))) > + (cons replacement result) > + result))) > + '() > + > + ;; Dismiss deprecated packages but keep hidden packages. > + #:select? (negate package-superseded)))) > + (append > + packages > + non-exported-replacement-packages))) Is the goal to delete duplicates? In that case, how about wrapping the existing expression in (delete-duplicates … eq?) ? (Note that (member x lst) is O(N) is the number of packages, so the code above is quadratic in the number of packages, which should be avoided. Also, packages cannot be meaningfully compared with ‘equal?’ (which is expensive in case of different packages), so ‘eq?’ should be preferred.) Thanks, Ludo’.
Ludovic Courtès <ludo@gnu.org> writes: > Hi! > > Christopher Baines <mail@cbaines.net> skribis: > >> There could be performance issues with member here, but only if there are lots >> of replacements. >> >> * guix/scripts/weather.scm (all-packages): Return all exported packages, plus >> non exported replacements, rather than including exported replacements twice. > > [...] > >> + "Return the list of packages we are going to query." >> + (let* ((packages >> + (fold-packages (lambda (package result) >> + (cons package result)) >> + '() >> + >> + ;; Dismiss deprecated packages but keep hidden packages. >> + #:select? (negate package-superseded))) >> + (non-exported-replacement-packages >> + (fold-packages (lambda (package result) >> + (let ((replacement (package-replacement package))) >> + (if (and replacement >> + ;; Avoid double couting replacements >> + ;; that are themselves exported >> + (not (member replacement packages))) >> + (cons replacement result) >> + result))) >> + '() >> + >> + ;; Dismiss deprecated packages but keep hidden packages. >> + #:select? (negate package-superseded)))) >> + (append >> + packages >> + non-exported-replacement-packages))) > > Is the goal to delete duplicates? Not really, the goal is to have a list with no duplicates. > In that case, how about wrapping the existing expression in > (delete-duplicates … eq?) ? > > (Note that (member x lst) is O(N) is the number of packages, so the code > above is quadratic in the number of packages, which should be avoided. > Also, packages cannot be meaningfully compared with ‘equal?’ (which is > expensive in case of different packages), so ‘eq?’ should be preferred.) Replacing member with memq seems sensible. My understanding of delete duplicates is that it's O(N^2), because it constructs a new list, and keeps searching it in linear time. While that sounds better, doing a linear search of packages for each replacement should be quicker, assuming there's only a few replacements compared to the number of packages. I'm fine with either though, I don't actually know which is faster, and it probably doesn't matter anyway. I'll send a patch with a delete-duplicates approach.
diff --git a/guix/scripts/weather.scm b/guix/scripts/weather.scm index 06312d65a2..0f70dc8460 100644 --- a/guix/scripts/weather.scm +++ b/guix/scripts/weather.scm @@ -53,17 +53,30 @@ #:export (guix-weather)) (define (all-packages) - "Return the list of public packages we are going to query." - (fold-packages (lambda (package result) - (match (package-replacement package) - ((? package? replacement) - (cons* replacement package result)) - (#f - (cons package result)))) - '() - - ;; Dismiss deprecated packages but keep hidden packages. - #:select? (negate package-superseded))) + "Return the list of packages we are going to query." + (let* ((packages + (fold-packages (lambda (package result) + (cons package result)) + '() + + ;; Dismiss deprecated packages but keep hidden packages. + #:select? (negate package-superseded))) + (non-exported-replacement-packages + (fold-packages (lambda (package result) + (let ((replacement (package-replacement package))) + (if (and replacement + ;; Avoid double couting replacements + ;; that are themselves exported + (not (member replacement packages))) + (cons replacement result) + result))) + '() + + ;; Dismiss deprecated packages but keep hidden packages. + #:select? (negate package-superseded)))) + (append + packages + non-exported-replacement-packages))) (define (call-with-progress-reporter reporter proc) "This is a variant of 'call-with-progress-reporter' that works with monadic