Re^2: Add a fixed number of unique elements to hash

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Re^3: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by kcott (Archbishop) on Mar 05, 2023 at 22:20 UTC
G'day tybalt89, When initially writing the code in my response, I checked the List::Util::shuffle() documentation and noticed the `sample()` function immediately after it. I hadn't encountered that previously and decided to give it a go. Curiously, although it did work as documented, multiple runs produced the same results. As you can see from my "sample runs" using `shuffle()`, multiple runs produced different results (yes, only two runs shown, but I did run it quite a few times). Looking at source/lib/List/AllUtils.pm, `List::AllUtils::sample()` should be identical to `List::Util::sample()`. I have List::Util v1.62 and Perl v5.36.0. I'm a bit short on time this morning; I was thinking of investigating further this afternoon [Aussie timezone: UTC+11:00]. If you have any insights into the behaviour of `sample()`, please share. It did seem like `sample()`, taking a random selection from the array, was probably a better choice than `shuffle()`, randomising the entire array and then taking a slice (obviously, benchmarking needed to confirm this). On the down side, `sample()` requires `List::Util v1.54`: you'd need at least Perl v5.32.0 (which has v1.55) or an upgrade from CPAN. — Ken	[reply] [d/l] [select]
Re^4: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by hippo (Archbishop) on Mar 07, 2023 at 10:50 UTC
I have a slightly newer verison of List::Util here (1.63 as below) and `sample` appears to work as intended, ie. different runs produce different results: `$ pmv List::Util 1.63 $ perl -MList::Util=sample -wE 'my @x=("a".."z"); say sample (3, @x)' jso $ perl -MList::Util=sample -wE 'my @x=("a".."z"); say sample (3, @x)' ter $ perl -MList::Util=sample -wE 'my @x=("a".."z"); say sample (3, @x)' mgl $ perl -MList::Util=sample -wE 'my @x=("a".."z"); say sample (3, @x)' ago $` [download] There's nothing in the List::Util changelog to indicate any modification to `sample` so either some other fix has had an effect or something else is at play. 🦛	[reply] [d/l] [select]
Re^5: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by kcott (Archbishop) on Mar 07, 2023 at 12:07 UTC
G'day hippo, ++ Thanks for checking that out. I ran a verbatim copy of your one-liner four times and got a different result each time; so, on the face of it, this seems to be working correctly (with `v1.62` & `v1.63`). I did actually sit down to run some tests yesterday; unfortunately, real-life barged in and the testing needed to take a backseat. I will get to it eventually. I'm fairly certain that I didn't change any logic when moving from `sample` to `shuffle`. I recall only a very minor modification; probably just these two lines (off the top of my head): `#use List::Util 'sample'; use List::Util 'shuffle'; ... #my @playlist = sample $list_length, @all_files; my @playlist = (shuffle @all_files)[0 .. $list_length - 1];` [download] I'll post more when I get to the testing. It's 11pm here now, so that won't be tonight. :-) — Ken	[reply] [d/l] [select]
Re^4: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by Vasek (Acolyte) on Mar 05, 2023 at 23:13 UTC
Many thanks for your replies and testing, but the target machine is running Perl 5.004 (unfortunately I wasn't precise enough when I just wrote Perl 5). The final solution was to use splice as suggested by jwkrahn in the next post.	[reply]
Re^5: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by davido (Cardinal) on Mar 06, 2023 at 03:41 UTC
What kind of machine are you running Perl 5.004 on? Seriously, you've peaqued my curiosity. You have some old desktop system from 1998 up and running? Anything newer than that, you would have upgraded to a more modern version of Perl long ago. Perl 5.004 is 25 years old. Dave	[reply]
Re^6: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by Vasek (Acolyte) on Mar 06, 2023 at 10:56 UTC
Re^7: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by cavac (Prior) on Mar 06, 2023 at 13:59 UTC
Re^7: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by davido (Cardinal) on Mar 06, 2023 at 19:22 UTC
Re^6: Add a fixed number of unique elements to hash [sample() vs. shuffle()] by hippo (Archbishop) on Mar 06, 2023 at 09:53 UTC
Re^3: Add a fixed number of unique elements to hash by jo37 (Curate) on Mar 06, 2023 at 20:24 UTC
Be careful with `List::AllUtils`. "All" isn't really "all". At least `frequency` from `List::MoreUtils` is missing. I prefer to `use` the original modules. Greetings, -jo `$gryYup$d0ylprbpriprrYpkJl2xyl~rzg??P~5lp2hyl0p$`	[reply] [d/l] [select]
Re^4: Add a fixed number of unique elements to hash by tybalt89 (Monsignor) on Mar 06, 2023 at 21:57 UTC
Probably because of `use List::AllUtils qw( count_by ); %frequencies = count_by { $_ } LIST;` [download]	[reply] [d/l]