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Comment by gleenn | Hacker News Reader

Level0 was fun, Level1 threw me immediately into "This looks like it's gonna suck". I know Git fairly well, but I don't know it that well. I poked at the shell script a bit, but I just ain't seeing it. It's also a lot harder to work on without the support of the easy benchmarking ability that was provided in Level0. How do I know if I'm actually improving.

Props in general, I just feel like Level1 was kind of a brick wall for me.

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I thought the shell script was actually a really great way of introducing you to the subject. You can basically look at the script, make out the "hot" part, optimize that part and you're done.

How would you optimise internal git commands or a loop that will still need to brute-force either way?

Rot13 for spoilers:

Jura vaibxvat tvg va n furyy ybbc, lbh'er jnfgvat lbhe gvzr sbexvat. Qbvat guvf va n fvatyr cebprff jvyy fcrrq vg hc n ybg.

That's what I suspected. So essentially, mimic that git command in bash without calling the git command (including the header stuff)?

It's not calling the git command that's problematic, it's calling an external command at all. So you pretty much have to recode the hot part in another language, where you just manipulate buffers instead of piping stuff around.

I did exactly that but my SHA-1 (in Ruby) is ending up different than Git's. Even weirder, when I take the header + body, and use an online SHA-1, I get a third and different value! (Not equal to git-hash-object nor to mine in Ruby). Is the body supposed to be modified to add LEDGER content?

do you have 'commit $body.length\0'?

This was the part that I stumbled on for a few hours late at night and kept me up. Next morning, when investigating what git hash-object did, it was obvious. should have just went to sleep.

Look again at Object Storage under the Git Objects link and you should get it, you're probably not quite matching what it does, it is a simple SHA1 so you're probably just missing one little part of the string to hash. You're on the right track - test getting the hashes to match first with git hash-object, but once you have done that you just need to solve it faster and recover when you discover that someone else got there first.

It is possible in ruby, that's what I used first, though the ref implementation is in ruby, so a single process may not cut it unless you are lucky. Keep trying too if you are solving it but not quite making it in time as you're competing against a variable time to complete on the other side.

You don't have to use bash, or just one process. You can completely replace their solution as long as you do roughly the same thing and they can run your binary (C, python, ruby, java, whatever).

The link to the git docs is fairly illuminating - there's only a very small part you need to understand. In particular, look at Object Storage under the Git Objects link.

It is a bit tricky because you're competing against random timings for the bot miners, but you need to mine before the bots do, so you need to speed up finding a commit hash, then do the commit. I hope that is useful without giving too much away.

yes i felt the same

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