in reply to Re: Size of Judy::HS array: where is MemUsed()?
in thread Size of Judy::HS array: where is MemUsed()?

G'day eyepopslikeamosquito,

Thanks for this. I do remember the "Rosetta Code: Long List is Long" thread — in fact, I front-paged it — and I did follow it for some time. There are certainly things of interest. I've packed up my tinkering for now (heading off for a major family "Easter" reunion) but will no doubt get back to it next week.

Your first reference brought Memory::Usage to my attention. I don't recall using that module, or even being aware of it, previously. It could provide common ground for comparing sizes: currently using Devel::Size::total_size() for %hash and Judy::HS::MemUsed() for $judy. It would also get around the MemUsed() bug(s) already discussed.

I came across Judy arrays quite some time ago: I added it to my mental list of things to study further at some future date. Curiously, I came across your third reference a couple of days ago (via some link hopping around PM): this prompted me to move Judy arrays from the mental list to the active list. :-)

— Ken

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Re^3: Size of Judy::HS array: where is MemUsed()?
by marioroy (Prior) on Apr 10, 2023 at 20:59 UTC

    G'day kcott,

    During the "Rosetta Code: Long List is Long" experiment, I called the JudySL/HS free functions in C to obtain the amount of memory used. The Judy::HS Perl module also returns bytes. Judy::HS wowed me regarding memory utilization versus native hash. I did not call MemUsed at the time.

    my bytes = Free( $Judy );

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      G'day Mario,

      Thanks for the feedback. As mentioned earlier, this was put on hold for a family Easter event; I expect to be working on it again this week.

      My main concern with MemUsed() was the bug(s) reported by hv: if I were to present Judy::HS to $work, as a buggy module, which needed patching, and appeared to be abandonware, it probably wouldn't be received too well. Using Memory::Usage instead of MemUsed() would circumvent this problem; other parts of Judy::HS seem solid (from what I've read).

      Early results do show that Judy::HS used a lot less memory than %hash.

      I initially used /usr/share/dict/australian-english to populate the hash keys. I chose this because it was the largest of several files I have in /usr/share/dict/ (the fact that I'm an Aussie was only a secondary consideration); however, I found that this file has entries with characters outside the 7-bit ASCII range (e.g. Ångström). This required some encoding manipulation for Judy::HS; creating this data structure was slower than for a %hash.

      /usr/share/dict/linux.words is the smallest in that directory and, as far as I can tell, only uses 7-bit ASCII. I'll be giving that a try to see how Judy::HS fares against %hash when there's no encoding consideration.

      There's other areas I intend to address, which will likely include: reading the data structures with and without encoding; non-integer values; and, complex structures (e.g. HoH).

      All very interesting; there should be a Meditation somewhere down the track with results of this investigation.

      — Ken

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