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Writing Efficient C++ Code (2013)

176 points · 161 comments · ibobev

  1. hn_submit · · focus · HN ↗
    I write in C++ almost every day but never have the need to optimize for speed. Even when you write straightforward code it's already blazingly fast.
    1. glouwbug · · focus · HN ↗
      True, but moving from a list of unique polymorphic pointers to a std::variant gains you at least a 2-3x speed up in terms of TLB and cacheline locality. From there, swapping to SOA will net you another 4-8x, so you're looking at nearly 25x improvement by going data first. That may not matter in the unique case of say, games, where rendering a million entities will dwarf the cost of SIMD processing a million entities, but in something like numerical simulations (fluids) or quant it will be warmly welcomed
      1. someonebaggy · · focus · HN ↗
        You don't render a million entities, only the ones that are actually on-screen. But when you do render them, you also want to render them in SoA style, culling them by comparing all the bounding boxes against the view frustum, generating a single big list of draw commands and passing it to draw-indirect one time.
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