4 ms·

Have you ever attempted to write a scripting language that performs better? I have, several, and it's far from trivial. The basics are seriously optimized for

by codr7 3y ago

Have you ever attempted to write a scripting language that performs better? I have, several, and it's far from trivial. The basics are seriously optimized for typical use cases, take a look at the source code for the dict type.

svieira 3y ago
Raymond Hettinger's talk Modern Python Dictionaries: A confluence of a dozen great ideas is an awesome "history of how we got these optimizations" and a walk through why they are so effective - https://www.youtube.com/watch?v=npw4s1QTmPg https://www.youtube.com/watch?v=npw4s1QTmPg
- codr7 3y ago
  Yeah, I had a nice chat with Raymond Hettinger at a Pycon in Birmingham/UK back in the days (had no idea who he was at the time). He seemed like a dedicated and intelligent person, I'm sure we can thank him for some of that.
crabbone 3y ago
> Have you ever attempted to write a scripting language that performs better? No, because "scripting language" is not a thing. But, if we are talking about implementing languages, then I worked with many language implementations. The most comparable one that I know fairly well, inside-and-out would be the AVM, i.e. the ActionScript Virtual Machine. It's not well-written either unfortunately. I've looked at implementations of Lua, Emacs Lisp and Erlang at different times and to various degree. I'm also somewhat familiar with SBCL and ECL, the implementation side. There are different things the authors looked for in these implementations. For example, SBCL emphasizes performance, where ECL emphasizes simplicity and interop with C. If I had to grade language implementations I've seen, Erlang would absolutely take the cake. It's a very thoughtful and disciplined program where authors went to a great length to design and implement it. CPython is on the lower end of such programs. It's anarchic, very unevenly implemented, you run into comments testifying to the author not knowing what they are doing, what their predecessor did, nor what to do next. Sometimes the code is written from that perspective as well, as in if the author somehow manages to drive themselves in the corner they don't know what the reference count is anymore, they'll just hammer it until they hope all references are dead (well, maybe). It's the code style that, unfortunately, I associate with proprietary projects where deadlines and cost dictate the quality, where concurrency problems are solved with sleeps, and if that doesn't work, then the sleep delay is doubled. It's not because I specifically hate code being proprietary, but because I meet that kind of code in my day job more than I meet it in hobby open-source projects. > take a look at the source code for the dict type. I wrote a Protobuf parser in C with the intention of exposing its bindings to Python. Dictionaries were a natural choice for the hash-map Protobuf elements. I benchmarked my implementation against C++ (Google's) implementation only to discover that std::map wins against Python's dictionary by a landslide. Maybe Python's dict isn't as bad as most of the rest of the interpreter, but being the best of the worst still doesn't make it good.
- codr7 3y ago
  Except it is, because everyone knows sort of what it means, an interpreted language that prioritizes convenience over performance; Perl/Python/Ruby/Lua/PHP/etc. SBCL is definitely a different beast. I would expect Emacs Lisp & Lua to be more similar. Erlang had plenty more funding and stricter requirements. C++'s std::map has most likely gotten even more attention than Python's dict, but I'm not sure from your comment if you're including Python's VM dispatch in that comparison. What are you trying to prove here?
  - JonChesterfield 3y ago
    (std::map is famously rubbish, to the extent that a common code review fix is to replace it with std::unordered_map. Map is a tree, unordered map is a linked-list-collision hashtable. Both are something of a performance embarrassment for C++. So std::map outperforming a given hashtable is a strongly negative judgement)
    - codr7 3y ago
      It's ordered and predictable, which is far from rubbish. In most cases std::unordered_map will be faster, but hashtables have nasty edge cases and are usually more expensive to create. I can pretty much guarantee it's been optimized to hell and back.
      - JonChesterfield 3y ago
        Unordered map sure hasn't been. There are algorithmic performance guarantees in the standard that force the linked list of buckets implementation despite that being slower than alternatives. Maybe the libc++ map<> is a very perfect rbtree, but I doubt that's the state of the art in ordered containers either.
    - crabbone 3y ago
      If I may hazard a guess (I don't know why the original code used it), Python dictionaries are also ordered (and there's no option in Python's library to have them not ordered). Maybe they wanted to match Python's behavior.
wahern 3y ago
> The basics are seriously optimized for typical use cases, take a look at the source code for the dict type Python is well micro-optimized, but the broader architecture of the language and especially the CPython implementation did not put much concern into performance, even for a dynamically typed scripting language. For example, in CPython values of built-in types are still allocated as regular objects and passed by reference; this is atrocious for performance and no amount of micro optimization will suffice to completely bridge the performance gap for tasks which stress this aspect of CPython. By contrast, primitive types in Lua (including PUC Lua, the reference, non-JIT implementation) and JavaScript are passed around internally as scalar values, and the languages were designed with this in mind. Perl is similar to Python in this regard--the language constructs and type systems weren't designed for high primitive operation throughput. Rather, performance considerations were focused on higher level, functional tasks. For example, Perl string objects were designed to support fast concatenation and copy-on-write references, optimizations which pay huge dividends for the tasks for which Perl became popular. Perl can often seem ridiculously fast for naive string munging compared to even compiled languages, yet few people care to defend Perl as a performant language per se.
rowanG077 3y ago
> Have you ever attempted to write a scripting language that performs better? Way to miss the mark. The point is precisely that Python is slow and one of the causes is that it is a scripting language. Stomping your foot and essentially: "You couldn't do any better" helps no one and is counterproductive.

by codr7 3y ago

svieira 3y ago

Raymond Hettinger's talk Modern Python Dictionaries: A confluence of a dozen great ideas is an awesome "history of how we got these optimizations" and a walk through why they are so effective - https://www.youtube.com/watch?v=npw4s1QTmPg https://www.youtube.com/watch?v=npw4s1QTmPg

codr7 3y ago
Yeah, I had a nice chat with Raymond Hettinger at a Pycon in Birmingham/UK back in the days (had no idea who he was at the time). He seemed like a dedicated and intelligent person, I'm sure we can thank him for some of that.

crabbone 3y ago

> Have you ever attempted to write a scripting language that performs better? No, because "scripting language" is not a thing. But, if we are talking about implementing languages, then I worked with many language implementations. The most comparable one that I know fairly well, inside-and-out would be the AVM, i.e. the ActionScript Virtual Machine. It's not well-written either unfortunately. I've looked at implementations of Lua, Emacs Lisp and Erlang at different times and to various degree. I'm also somewhat familiar with SBCL and ECL, the implementation side. There are different things the authors looked for in these implementations. For example, SBCL emphasizes performance, where ECL emphasizes simplicity and interop with C. If I had to grade language implementations I've seen, Erlang would absolutely take the cake. It's a very thoughtful and disciplined program where authors went to a great length to design and implement it. CPython is on the lower end of such programs. It's anarchic, very unevenly implemented, you run into comments testifying to the author not knowing what they are doing, what their predecessor did, nor what to do next. Sometimes the code is written from that perspective as well, as in if the author somehow manages to drive themselves in the corner they don't know what the reference count is anymore, they'll just hammer it until they hope all references are dead (well, maybe). It's the code style that, unfortunately, I associate with proprietary projects where deadlines and cost dictate the quality, where concurrency problems are solved with sleeps, and if that doesn't work, then the sleep delay is doubled. It's not because I specifically hate code being proprietary, but because I meet that kind of code in my day job more than I meet it in hobby open-source projects. > take a look at the source code for the dict type. I wrote a Protobuf parser in C with the intention of exposing its bindings to Python. Dictionaries were a natural choice for the hash-map Protobuf elements. I benchmarked my implementation against C++ (Google's) implementation only to discover that std::map wins against Python's dictionary by a landslide. Maybe Python's dict isn't as bad as most of the rest of the interpreter, but being the best of the worst still doesn't make it good.

codr7 3y ago
Except it is, because everyone knows sort of what it means, an interpreted language that prioritizes convenience over performance; Perl/Python/Ruby/Lua/PHP/etc. SBCL is definitely a different beast. I would expect Emacs Lisp & Lua to be more similar. Erlang had plenty more funding and stricter requirements. C++'s std::map has most likely gotten even more attention than Python's dict, but I'm not sure from your comment if you're including Python's VM dispatch in that comparison. What are you trying to prove here?
- JonChesterfield 3y ago
  (std::map is famously rubbish, to the extent that a common code review fix is to replace it with std::unordered_map. Map is a tree, unordered map is a linked-list-collision hashtable. Both are something of a performance embarrassment for C++. So std::map outperforming a given hashtable is a strongly negative judgement)
  - codr7 3y ago
    It's ordered and predictable, which is far from rubbish. In most cases std::unordered_map will be faster, but hashtables have nasty edge cases and are usually more expensive to create. I can pretty much guarantee it's been optimized to hell and back.
    - JonChesterfield 3y ago
      Unordered map sure hasn't been. There are algorithmic performance guarantees in the standard that force the linked list of buckets implementation despite that being slower than alternatives. Maybe the libc++ map<> is a very perfect rbtree, but I doubt that's the state of the art in ordered containers either.
  - crabbone 3y ago
    If I may hazard a guess (I don't know why the original code used it), Python dictionaries are also ordered (and there's no option in Python's library to have them not ordered). Maybe they wanted to match Python's behavior.

wahern 3y ago

> The basics are seriously optimized for typical use cases, take a look at the source code for the dict type Python is well micro-optimized, but the broader architecture of the language and especially the CPython implementation did not put much concern into performance, even for a dynamically typed scripting language. For example, in CPython values of built-in types are still allocated as regular objects and passed by reference; this is atrocious for performance and no amount of micro optimization will suffice to completely bridge the performance gap for tasks which stress this aspect of CPython. By contrast, primitive types in Lua (including PUC Lua, the reference, non-JIT implementation) and JavaScript are passed around internally as scalar values, and the languages were designed with this in mind. Perl is similar to Python in this regard--the language constructs and type systems weren't designed for high primitive operation throughput. Rather, performance considerations were focused on higher level, functional tasks. For example, Perl string objects were designed to support fast concatenation and copy-on-write references, optimizations which pay huge dividends for the tasks for which Perl became popular. Perl can often seem ridiculously fast for naive string munging compared to even compiled languages, yet few people care to defend Perl as a performant language per se.

rowanG077 3y ago

> Have you ever attempted to write a scripting language that performs better? Way to miss the mark. The point is precisely that Python is slow and one of the causes is that it is a scripting language. Stomping your foot and essentially: "You couldn't do any better" helps no one and is counterproductive.