Ep 9: Some ideas #45
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Ep 9: Some ideas #45
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This is a CLI app. It deserves proper argument parsing and stuff. This has the side effect of collecting the files into a Vec but if you pass so many files that this matters you are doing some weird stuff
Super tiny thing but why not support people's non UTF8 file names?
This is very unhelpful:
error[E0387]: cannot borrow data mutably in a captured outer variable in an `Fn` closure
--> src/main.rs:30:57
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30 | .for_each(|filename| tally_words(filename, &mut words).unwrap());
| ^^^^^
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help: consider changing this closure to take self by mutable reference
--> src/main.rs:30:19
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30 | .for_each(|filename| tally_words(filename, &mut words).unwrap());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This creates a new HashMap in each `tally_words` call. We can thus omit using a Mutex. Instead of doing `for_each` with side effects, we use `reduce` (Rayon's parallel version of it) to build the final map of words. The reason I used the im crate is because it has a very nice `union_with` method on its HashMap; you can also replace `im::HashMap` with `im::OrdMap` if you want to get sorted output directly. I have no idea if this is faster, but it does show a different way of using concurrency.
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As always, top notch work by @killercup. |
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Thanks! Added. |
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Very interesting approach, well done! |
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Hey, after watching episode 9 I wanted to play around with another way of doing this: Instead of using a Mutex, we can also create a new hash map each time and combine them later on in a reduce. And Rayon has a pretty nice way of doing that.
I have not done any benchmarks whatsoever. See commit messages for more details.