3 ms·

Accessing RAM sometimes costs extra log(N)

• Tojot 10y ago
  In response to "The Myth of RAM" https://news.ycombinator.com/item?id=12383012 https://news.ycombinator.com/item?id=12383012 It so happens that a large part of my PhD was on this very subject. The result I've got N log(N), this is more visible when you get to larger RAM (I had 0,5 TB RAM at the time). We have an empirical result, a justification and a rigorous predictive model. The reason has to do with hashing, but a different type: TLB. Feel free to take a look at a free copy at http://arxiv.org/abs/1212.0703 http://arxiv.org/abs/1212.0703 where we establish the VAT cost model.
  • corysama 10y ago
    Very interesting and informative. I would have expected a TLB to incur an additional cost beyond exhausting the cache hierarchy. But, I would have expected it to be a single additional cliff around a gig at most. Shame there's no discussion here. I've x-posted to https://www.reddit.com/r/programming/comments/509qhd/randomly_accessing_n_items_in_dram_is_on_in/ https://www.reddit.com/r/programming/comments/509qhd/randoml... Maybe that will drum up a bit more conversation.
    • Tojot 10y ago
      Thanks! Looks like it worked.
• deleted 10y ago
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