ustring hash improvements #1
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Amending this review with an improved hash function that generates many fewer collisions. (See discussion on oiio-dev) |
…lacement of the tile & file mutexes to avoid false sharing (moving them from next to each other to next to the structures they protect).
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I think I've made all the mods to address Chris' comments. |
…e expect m_validspec to be true, not at this point any more.
…cheFile refactor.
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Sorry, I think I made the mistake of merging upstream fixes and that has muddied up the diffs here by incorporating those other committed changes. Chris, have I addressed your earlier comments? |
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LGTM |
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Wait a second ... I think I had made a comment which got lost ? Changing the hash to be size_t is bad as it changes the hash on 64 bit platforms. Its designed to be a 32 bit hash. |
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Make the ustring statistics include info on hash collisions -- how many collisions (non-unique hashes), the max number of strings sharing a non-unique hash, and in debug mode the strings sharing the most-shared hash.
We think this is all harmless, but this stat allows us to reassure ourselves that hash collisions aren't hurting performance or becoming pathological.
Update: also replaced the hash function with one that has vastly fewer collisions.