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Oh, I'd missed those solutions, thanks. You guys got way more hard core than I did -- nice work! Looking forward to reading the code for those solutions this week.

Update: for reference, Jason Chu's solution (https://github.com/dhartunian/1brcgo/blob/494eabd6ea958cc193...) seems to be the fastest on my machine, and runs in about 1.3s!

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I think we all ended up using unsafe, though there were some solutions without mmap. It would have been interesting if we had adhered to the same constraints you did!

Could you say why you find using memory-mapped files to be a portability issue? Thanks.

Well, I guess it's more that the standard library doesn't have a cross-platform way to access them, not that memory-mapped files themselves can't be done on (say) Windows. It looks like there's a fairly popular 3rd party package that supports at least Linux, macOS, and Windows: https://github.com/edsrzf/mmap-go

Not all filesystems support memory-mapped files equally, and for some that do, the support comes with caveats and could be slower than non-memory-mapped access.

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