Make a faster HASH_ITER macro and make other hash optimizations #901
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AlexDaniel
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Jul 9, 2018
src/strings/uthash.h
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| #define HASH_CNT(hh,head) ((head)?((head)->hh.tbl->num_items):0) | ||
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| MVM_STATIC_INLINE unsigned GET_X_BITS_FUNCT(MVMuint64 bucket_rand, unsigned log2_num_buckets) { | ||
| switch (log2_num_buckets) { |
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Also optimize GET_X_BITS by making a switch out of it. It doesn't seem
like this would be faster, but it is due to compiler optimizations.
Maybe it needs a comment here saying that it is done this way because it's faster? Otherwise someone may refactor it months later :)
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HASH_ITER_FAST is faster and it doesn't randomize bucket order (though it's faster regardless of that). Makes the biggest difference when we are iterating a hash with a LOT of keys in it, such as adding a million keys to a hash then deleting and adding back again. Got about 40% speed improvement on this nqp script: https://gist.github.com/9a65a586ea21b20def8efe4aaaab55de Most of the time spent in the above script was in MVMHash_gc_mark, and that now uses the fast iterator internally which results in the speed improvement. Also optimize GET_X_BITS by making a switch out of it. It doesn't seem like this would be faster, but it is due to compiler optimizations.
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HASH_ITER_FAST is faster and it doesn't randomize bucket order (though
it's faster regardless of that).
Makes the biggest difference when we are iterating a hash with a LOT of
keys in it, such as adding a million keys to a hash then deleting and
adding back again. Got about 40% speed improvement on this nqp script:
https://gist.github.com/9a65a586ea21b20def8efe4aaaab55de
Also optimize GET_X_BITS by making a switch out of it. It doesn't seem
like this would be faster, but it is due to compiler optimizations.