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I am learning Rust due to it's memory safety features and comments like this rub me the wrong way for some reason -- they give me an uneasy feeling that I will

by grok22 7y ago

I am learning Rust due to it's memory safety features and comments like this rub me the wrong way for some reason -- they give me an uneasy feeling that I will run into unexpected limitations in the language because these corners are not exercised enough. Because people who know the language are saying that the kind of data-structures that I deal with day in and out in my day-to-day work are not the "preferred" thing to do. I do system software/networking software and I deal with a lot of linked lists and trees and these comments make me feel that Rust may not be a good language for my use-case in-spite of me wanting the memory safety features.

mkesper 7y ago
It's just not needed to implement trivial data structures by yourself if it's already implemented before. Also linked lists might be sub-optimal, see other comments.
jdsully 7y ago
The comment applies word for word to C++ as well. Linked lists are just bad datastructures for modern CPUs. I don’t use rust so I can’t speak to the quality of the std lib, but I don’t think its fair to use the parent comment as evidence either way.
- blub 7y ago
  No, it doesn't apply to C++ because the corners of the language required to write lists and trees are exercised enough and don't suffer from unexpected limitations.
  - jdsully 7y ago
    The comment originating this discussion provides no evidence in any direction on the quality of the rust standard library. Merely that you wouldn't use these in practice, nor would you in C++.
pas 7y ago
Do you currently use C? C++ perhaps? I mean basically no other language that currently comes to mind fiddles so much with the basics. In Rust, just as in Java, people write highly optimized safe and fast data structures and others build upon that. In C/C++ it seems every project reinvents the wheel to a large degree. Or am I mistaken?
- bobbiechen 7y ago
  >In Rust, just as in Java, people write highly optimized safe and fast data structures and others build upon that. I'm currently taking a class on API design with Josh Bloch (Java Collections, Effective Java, etc.), who pointed out that this wasn't the case until the late 90s or so - he pulled out an example of a KWIC system [1] described in a paper [2] from 1971: Parnas 1971: This is a small system [that] could be produced by a good programmer within a week or two. And then Josh proceeded to show his implementation of the same system, which he had written in <2 hours just by making use of the built-in collections, regular expressions, sorting, string formatting, etc. It's really cool that these standard data structure implementations exist and are so accessible, making people orders of magnitude faster than before. [1] https://en.wikipedia.org/wiki/Key_Word_in_Context https://en.wikipedia.org/wiki/Key_Word_in_Context [2] https://prl.ccs.neu.edu/img/p-tr-1971.pdf https://prl.ccs.neu.edu/img/p-tr-1971.pdf
- grok22 7y ago
  I use C. And you are right, in my field there is a tendency to a large degree to re-invent the wheel of data-structures :-). Sometimes justified, but most times not. But mostly because C doesn't usually have well-known, industry-standard libraries for common data-structures. Or even if they do, it's kind of trivial to implement basic data-structures (not saying they will be bug-free!) instead of relying on some random distribution of a library from the Internet. BTW, most times, the problem is not performance, but tight control of memory usage.
  - throwaway17_17 7y ago
    I think your point about control of memory usage is spot on. Most conversations tend toward cycle count and execution speed and fail to consider memory usage at all (I know I’m certainly guilty of it).
btilly 7y ago
Don't worry. The language has lots of support for the style you wish to work in. As for the specific data structures, I recommend setting aside your knowledge of their utility and consider carefully why they are being criticized. Then run some experiments to convince yourself of what is true. If you come to the conclusion that the criticisms make sense, then you can proceed with the knowledge that the people in question have thought about the issue and came to good decisions. This should inspire hope that they have thought about other issues as well and may have valuable insights. For the record, I concluded many years ago that some variant on arrays/vectors/whatever outperforms linked lists in most situations by a lot. (There are times when arrays/vectors/whatever can't work. But they are less common than most imagine.) And changes in hardware have made that more true over time. Trees, on the other hand, have a flexibility that lends itself to many problems that it is hard to find other structures for many use cases. But even so if performance is critical, it is worth jumping through a lot of hoops to make sure that all of the pointers that make up a tree are physically close together in memory to improve the efficiency of your caches.
dodobirdlord 7y ago
Linking my comment from elsewhere. https://news.ycombinator.com/item?id=22393723 https://news.ycombinator.com/item?id=22393723

by grok22 7y ago

mkesper 7y ago

It's just not needed to implement trivial data structures by yourself if it's already implemented before. Also linked lists might be sub-optimal, see other comments.

jdsully 7y ago

The comment applies word for word to C++ as well. Linked lists are just bad datastructures for modern CPUs. I don’t use rust so I can’t speak to the quality of the std lib, but I don’t think its fair to use the parent comment as evidence either way.

blub 7y ago
No, it doesn't apply to C++ because the corners of the language required to write lists and trees are exercised enough and don't suffer from unexpected limitations.
- jdsully 7y ago
  The comment originating this discussion provides no evidence in any direction on the quality of the rust standard library. Merely that you wouldn't use these in practice, nor would you in C++.

pas 7y ago

Do you currently use C? C++ perhaps? I mean basically no other language that currently comes to mind fiddles so much with the basics. In Rust, just as in Java, people write highly optimized safe and fast data structures and others build upon that. In C/C++ it seems every project reinvents the wheel to a large degree. Or am I mistaken?

bobbiechen 7y ago
>In Rust, just as in Java, people write highly optimized safe and fast data structures and others build upon that. I'm currently taking a class on API design with Josh Bloch (Java Collections, Effective Java, etc.), who pointed out that this wasn't the case until the late 90s or so - he pulled out an example of a KWIC system [1] described in a paper [2] from 1971: Parnas 1971: This is a small system [that] could be produced by a good programmer within a week or two. And then Josh proceeded to show his implementation of the same system, which he had written in <2 hours just by making use of the built-in collections, regular expressions, sorting, string formatting, etc. It's really cool that these standard data structure implementations exist and are so accessible, making people orders of magnitude faster than before. [1] https://en.wikipedia.org/wiki/Key_Word_in_Context https://en.wikipedia.org/wiki/Key_Word_in_Context [2] https://prl.ccs.neu.edu/img/p-tr-1971.pdf https://prl.ccs.neu.edu/img/p-tr-1971.pdf
grok22 7y ago
I use C. And you are right, in my field there is a tendency to a large degree to re-invent the wheel of data-structures :-). Sometimes justified, but most times not. But mostly because C doesn't usually have well-known, industry-standard libraries for common data-structures. Or even if they do, it's kind of trivial to implement basic data-structures (not saying they will be bug-free!) instead of relying on some random distribution of a library from the Internet. BTW, most times, the problem is not performance, but tight control of memory usage.
- throwaway17_17 7y ago
  I think your point about control of memory usage is spot on. Most conversations tend toward cycle count and execution speed and fail to consider memory usage at all (I know I’m certainly guilty of it).

btilly 7y ago

Don't worry. The language has lots of support for the style you wish to work in. As for the specific data structures, I recommend setting aside your knowledge of their utility and consider carefully why they are being criticized. Then run some experiments to convince yourself of what is true. If you come to the conclusion that the criticisms make sense, then you can proceed with the knowledge that the people in question have thought about the issue and came to good decisions. This should inspire hope that they have thought about other issues as well and may have valuable insights. For the record, I concluded many years ago that some variant on arrays/vectors/whatever outperforms linked lists in most situations by a lot. (There are times when arrays/vectors/whatever can't work. But they are less common than most imagine.) And changes in hardware have made that more true over time. Trees, on the other hand, have a flexibility that lends itself to many problems that it is hard to find other structures for many use cases. But even so if performance is critical, it is worth jumping through a lot of hoops to make sure that all of the pointers that make up a tree are physically close together in memory to improve the efficiency of your caches.

dodobirdlord 7y ago

Linking my comment from elsewhere. https://news.ycombinator.com/item?id=22393723 https://news.ycombinator.com/item?id=22393723