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Comment by jbapple

8 years ago

This post has some overconfident and under-researched claims:

> This came about because last year I wrote the fastest hash table (I still make that claim)

I'm extremely dubious of claims of the "fastest $DATA_STRUCTURE" without qualifiers about workload, hardware, and time/space trade-off. In particular, the last graph of this post shows some workloads (400k int keys, int[16] values, unsuccessful lookups) where the author's implementation of Swiss Table (as Google called their table) is 3x-10x slower than "bytell_hash_map", the author's own design.

> google_flat16_hash_map. This last one is my implementation of Google’s new hash table. Google hasn’t open-sourced their hash table yet, so I had to implement their hash table myself. I’m 95% sure that I got their performance right.

The talk announcing Swiss Table clearly didn't have enough detail to fully replicate their results. This 95% claim is rather astonishing in light of that.

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jbapple

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general_pizza  8 years ago

Hmm I’m seeing the opposite. The last graph shows Google’s hash table outperforming in all but a few places, including at 400k. Perhaps you mixed the axes up, lower is better here.

I also just want to comment that skepticism to high claims is good but your comment seems a bit too harsh. Briefly looking at his post where he goes into his “fastest hash table” it’s quite long, very detailed and has similar graphs. That doesn’t seem under-researched to me.

  • jbapple  8 years ago

    > Hmm I’m seeing the opposite. The last graph shows Google’s hash table outperforming in all but a few places, including at 400k.

    You're exactly right, General Pizza. I was trying to say that the Google table was faster, even though the author claimed that his or her table was "fastest" without qualification.

    Thanks for pointing that out; I'll leave my post as it is so yours continues to make sense in context.

coconutrandom  8 years ago

meta: classic HN, top post is a Negative Nancy regardless of how impressive the new thing is. Is there a name for this phenomena yet?

  • vanderZwan  8 years ago

    I know the type of post you talk about - dismissive easy critiques like "correlation does not.." - but GP's remark is not quite like that:

    - it states the article has some overconfident claims.

    - it gives detailed arguments for why

    > Is there a name for this phenomena yet?

    "bachelors' wives and maidens' children are well taught"?

  • nabla9  8 years ago

    No and there should not be. There unjustified critique and justified critique.

    ´