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| Perl: the Markov chain saw | |
| PerlMonks |
Re^5: Bidirectional lookup algorithm? (Judy)by BrowserUk (Patriarch) |
| on Jan 15, 2015 at 06:33 UTC ( [id://1113301]=note: print w/replies, xml ) | Need Help?? |
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For the record, I finally managed to build a static 64-bit library, too. Well done. And thank you for trying. Was that with Mingw or MSVC? I never managed to get beyond the Too early to specify a build action 'installdeps'. Do 'Build installdeps' instead. idiocy using MSVC. However, the Judy module that I built against the 64-bit library loaded ok, but kept crashing during the running of its test suite. In Judy.xs, I changed the hard coded "long" casts to "long long" casts. That got rid of lots of warnings during the build, but the crashing persisted. The generated Judy.c file still contained some casts to "unsigned long int" , but I couldn't immediately find what was generating those casts - at which point I totally lost interest. It's very capable code, but the very epitome of 'macro abuse'. The only way to work out what code is actually being compiled is to use /E and wade through the post processed source, but by then, you've no idea where the code came from; or what combination of #defines, #ifdefs and #ifndefs caused it. Like trying to listen to music by looking at an oscilloscope trace. That's why when I came across the 1 file version I linked, I jumped at it. It at least gave me a way to get a quick feel for the performance and memory usage -- both of which are very impressive -- until you have to make the Perl->XS->C and back transitions for every lookup :( Its not just the extra layers of function calls -- which I've tried to negate by forcing the functions to be inlined -- it also comes down to the fact that Perl code messes up the code and data caches as it leaps about all over memory chasing opcode trees. As the basis of Judy Array performance is the minimisation of cache misses, screwing with the cache between each access to those arrays, pretty much undoes everything the author worked so hard to achieve. Also, I think that my need to use two Judy arrays in parallel does nothing to enhance the performance. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
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