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Spending a weekend or two writing a Scheme that beats Python in performance has been a pastime for computer science students for at least a couple decades now.

Spending a weekend or two writing a Scheme that beats Python in performance has been a pastime for computer science students for at least a couple decades now. I'm not sure that I believe that a performant Scheme implementation has more complexity than e.g. PyPy. In fact, I'd wager the converse.

mrtranscendence 4y ago
You're either exaggerating or the computer science students you're familiar with are wizards. I've never known the student who could write a Scheme implementation, from scratch, in one weekend that is both complete and which beats Python from a performance perspective.
- peatmoss 4y ago
  If it's an exaggeration, it's not much of one. Two parts to your argument: - Writing a Scheme implementation quickly: Google "Write a Scheme in 48 hours" and "Scheme from scratch." 48 hours to a functioning Scheme implementation seems to be a feat replicated in multiple programming languages. - Performance: I haven't benchmarked every hobby scheme, but given the proliferation of Scheme implementations that, despite limited developer resources, beat (pure) Python with it's massive pool of developers (CPython, PyPy), I still don't buy the idea that optimizing Scheme is a harder task than optimizing Python. Again, I'd strongly suggest that optimizing Scheme is a much easier task than optimizing Python simply by virtue of how often the feat has been accomplished.
  - mrtranscendence 4y ago
    If you can give me an implementation that implements almost all of R5RS, in 48 hours, beating Python in performance, and all by a single developer, I’ll tip my hat to that guy or gal. But I can’t imagine it’s too commonly done.
    - eatonphil 4y ago
      Nobody said you can implement a full Scheme implementation in 48 hours or two weeks. That's very much besides the point about how poor CPython performance is.
      - mrtranscendence 4y ago
        > Nobody said you can implement a full Scheme implementation in 48 hours or two weeks. Fair enough, you're right. But if we're only talking about incomplete Scheme implementations it's not a very interesting claim. As I pointed out in another comment, even I could write a fast Scheme implementation in 48 hours if I kept my scope very limited. That doesn't say much about Scheme performance overall or how it relates to Python.
        eatonphil 4y ago
        What is it that you think makes a full Scheme implementation as slow as CPython?
        mrtranscendence 4y ago
        I don’t think a full Scheme implementation is as slow as Python in general. What I’m hung up on is the claim that it’s so absolutely trivial to write a language implementation faster than Python that basically anybody at any skill level could do it in a weekend, and still have time for Sunday afternoon bocce.
        pjmlp 4y ago
        Start with, "An Incremental Approach to Compiler Construction" http://scheme2006.cs.uchicago.edu/11-ghuloum.pdf http://scheme2006.cs.uchicago.edu/11-ghuloum.pdf
        peatmoss 4y ago
        Well let's flip this around: do you think you could write a performant minimal Python in a weekend? Scheme is a very simple and elegant idea. Its power derives from the fact that smart people went to considerable pains to distill computation to limited set of things. "Complete" (i.e. rXrs) schemes build quite a lot of themselves... in scheme, from a pretty tiny core. I suspect Jeff Bezanson spent more than a weekend writing femtolisp, but that isn't really important. He's one guy who wrote a pretty darned performant lisp that does useful computation as a passion project. Check out his readme; it's fascinating: https://github.com/JeffBezanson/femtolisp https://github.com/JeffBezanson/femtolisp You simply can't say these things about Python (and I generally like Python!). It's truer for PyPy, but PyPy is pretty big and complex itself. Take a look at the source for the scheme or scheme-derived language of your choice sometime. I can't claim to be an expert in any of what's going on in there, but I think you'll be surprised how far down those parens go. The claim I was responding to asserted that lisps and smalltalks can only be fast because of complex JIT compiling. That is trueish in practice for Smalltalk and certainly modern Javascript... but it simply isn't true for every lisp. Certainly JIT-ed lisps can be extremely fast, but it's not the only path to a performant lisp. In these benchmarks you'll see a diversity of approaches even among the top performers: https://ecraven.github.io/r7rs-benchmarks/ https://ecraven.github.io/r7rs-benchmarks/ Given how many performant implementations of Scheme there are, I just don't think you can claim it's because of complex implementations by well-resourced groups. To me, I think the logical conclusion is that Scheme (and other lisps for the most part) are intrinsically pretty optimizable compared to Python. If we look at Common Lisp, there are also multiple performant implementations, some approximately competitive with Java which has had enormous resources poured into making it performant.
  - eatonphil 4y ago
    I would not include PyPy in a list of easy to beat implementations.
    - JulianWasTaken 4y ago
      Nor ones with massive pools of developers.
      - peatmoss 4y ago
        Compared to most Scheme implementations?
- eatonphil 4y ago
  Substitute computer science student with "developer" and it holds for me. Definitely some CS students can do it too. Actually at my school we did have to implement a Scheme compiler. So yeah it's not too big of a stretch to say. I think people who haven't implemented a language underestimate how slow CPython is. And overestimate how hard it is to build a compiler for a dynamic language. I think every professional developer or CS student can and should build a compiler for a dynamic language!
  - mrtranscendence 4y ago
    But the claim was that a student could write a conformant Scheme implementation in 48 hours that beats Python. Clearly it’s possible for a student to write a Scheme that’s faster than Python, but is it a reasonably complete Scheme done in a single weekend? Even I, very much a non-computer scientist, could write a fast Scheme quickly if I could keep myself to a very small subset, so that’s not interesting to me.
    - eatonphil 4y ago
      Conformant is a word you introduced, they didn't say that.
- pjmlp 4y ago
  Only if they aren't attending degrees where compiler design is part of the curriculum, which if that is the case kind of speaks for the quality of the institution.
  - mrtranscendence 4y ago
    A reasonably complete, fast language implementation, from scratch, in one weekend, though? By someone who was only introduced to compilers within the last few months? I don’t believe most students would be capable of that, but I’m not a computer scientist so what do I know.
    - pjmlp 4y ago
      Yes, Scheme is quite simple, no one is speaking about doing R7RS. Compared with current state of affairs in CPython, even with basic code generation algorithms, the machine code would be fast enough. Introducing to compilers means also writing one in the process, unless it is a lousy degree.
munificent 4y ago
Sure, but that's because Python has objects. If your write an object system on top of your performant hobby Scheme implementation, you'll likely find that the performance of its method dispatch is about as slow as it is in Python. Probably even slower. Purely procedural Python code isn't as slow as object-oriented Python code.
- peatmoss 4y ago
  That's fair, but also the fact that we're comparing hobby scheme implementations to two mainstream extremely popular implementations of Python and setting up conditions that forces (hobby) Scheme to play to Python's relative strengths is telling. :-) The Python ecosystem has certainly received a lot of developer resources and attention the past couple of decades. Shall we compare the performance of CLOS on SBCL, which again has seen comparatively little developer resources, to Python's performance in dealing with objects? I'd take that performance wager.
  - Spivak 4y ago
    This isn’t as much of a gotcha as you think. Python is slow because the language is so dynamic and simply has to do more behind the scenes work on each line. It’s not impressive that a language that does less is faster. What’s impressive is that a language that does more, like JS on V8, is faster.
    - CraigJPerry 4y ago
      Is CLOS doing less than Python? I'm thinking CLOS has more dynamism than Python - they're both dynamically typed, they're both doing a lookup then dispatch, but then CLOS adds dynamism on top of that, it's also looking in the metadata thingy (i'm not a lisp developer, do they call it the hash? I'm meaning the key value store on every "atom" - i'm so out of my depth here, is atom the right word?) plus if i remember right the way CLOS works you use multiple dispatch not just single dispatch like python.
    - ByteJockey 4y ago
      The CLOS is more dynamic than python. You can do things like specialize a method on multiple types based on the runtime types (that is to say, the method conceptually belongs to the intersection of the classes, not any single class). I like python (especially things like comprehensions), but to say it's more dynamic than common lisp is a little insane.

mrtranscendence 4y ago

You're either exaggerating or the computer science students you're familiar with are wizards. I've never known the student who could write a Scheme implementation, from scratch, in one weekend that is both complete and which beats Python from a performance perspective.

peatmoss 4y ago
If it's an exaggeration, it's not much of one. Two parts to your argument: - Writing a Scheme implementation quickly: Google "Write a Scheme in 48 hours" and "Scheme from scratch." 48 hours to a functioning Scheme implementation seems to be a feat replicated in multiple programming languages. - Performance: I haven't benchmarked every hobby scheme, but given the proliferation of Scheme implementations that, despite limited developer resources, beat (pure) Python with it's massive pool of developers (CPython, PyPy), I still don't buy the idea that optimizing Scheme is a harder task than optimizing Python. Again, I'd strongly suggest that optimizing Scheme is a much easier task than optimizing Python simply by virtue of how often the feat has been accomplished.
- mrtranscendence 4y ago
  If you can give me an implementation that implements almost all of R5RS, in 48 hours, beating Python in performance, and all by a single developer, I’ll tip my hat to that guy or gal. But I can’t imagine it’s too commonly done.
  - eatonphil 4y ago
    Nobody said you can implement a full Scheme implementation in 48 hours or two weeks. That's very much besides the point about how poor CPython performance is.
    - mrtranscendence 4y ago
      > Nobody said you can implement a full Scheme implementation in 48 hours or two weeks. Fair enough, you're right. But if we're only talking about incomplete Scheme implementations it's not a very interesting claim. As I pointed out in another comment, even I could write a fast Scheme implementation in 48 hours if I kept my scope very limited. That doesn't say much about Scheme performance overall or how it relates to Python.
      - eatonphil 4y ago
        What is it that you think makes a full Scheme implementation as slow as CPython?
        mrtranscendence 4y ago
        I don’t think a full Scheme implementation is as slow as Python in general. What I’m hung up on is the claim that it’s so absolutely trivial to write a language implementation faster than Python that basically anybody at any skill level could do it in a weekend, and still have time for Sunday afternoon bocce.
        pjmlp 4y ago
        Start with, "An Incremental Approach to Compiler Construction" http://scheme2006.cs.uchicago.edu/11-ghuloum.pdf http://scheme2006.cs.uchicago.edu/11-ghuloum.pdf
      - peatmoss 4y ago
        Well let's flip this around: do you think you could write a performant minimal Python in a weekend? Scheme is a very simple and elegant idea. Its power derives from the fact that smart people went to considerable pains to distill computation to limited set of things. "Complete" (i.e. rXrs) schemes build quite a lot of themselves... in scheme, from a pretty tiny core. I suspect Jeff Bezanson spent more than a weekend writing femtolisp, but that isn't really important. He's one guy who wrote a pretty darned performant lisp that does useful computation as a passion project. Check out his readme; it's fascinating: https://github.com/JeffBezanson/femtolisp https://github.com/JeffBezanson/femtolisp You simply can't say these things about Python (and I generally like Python!). It's truer for PyPy, but PyPy is pretty big and complex itself. Take a look at the source for the scheme or scheme-derived language of your choice sometime. I can't claim to be an expert in any of what's going on in there, but I think you'll be surprised how far down those parens go. The claim I was responding to asserted that lisps and smalltalks can only be fast because of complex JIT compiling. That is trueish in practice for Smalltalk and certainly modern Javascript... but it simply isn't true for every lisp. Certainly JIT-ed lisps can be extremely fast, but it's not the only path to a performant lisp. In these benchmarks you'll see a diversity of approaches even among the top performers: https://ecraven.github.io/r7rs-benchmarks/ https://ecraven.github.io/r7rs-benchmarks/ Given how many performant implementations of Scheme there are, I just don't think you can claim it's because of complex implementations by well-resourced groups. To me, I think the logical conclusion is that Scheme (and other lisps for the most part) are intrinsically pretty optimizable compared to Python. If we look at Common Lisp, there are also multiple performant implementations, some approximately competitive with Java which has had enormous resources poured into making it performant.
- eatonphil 4y ago
  I would not include PyPy in a list of easy to beat implementations.
  - JulianWasTaken 4y ago
    Nor ones with massive pools of developers.
    - peatmoss 4y ago
      Compared to most Scheme implementations?
eatonphil 4y ago
Substitute computer science student with "developer" and it holds for me. Definitely some CS students can do it too. Actually at my school we did have to implement a Scheme compiler. So yeah it's not too big of a stretch to say. I think people who haven't implemented a language underestimate how slow CPython is. And overestimate how hard it is to build a compiler for a dynamic language. I think every professional developer or CS student can and should build a compiler for a dynamic language!
- mrtranscendence 4y ago
  But the claim was that a student could write a conformant Scheme implementation in 48 hours that beats Python. Clearly it’s possible for a student to write a Scheme that’s faster than Python, but is it a reasonably complete Scheme done in a single weekend? Even I, very much a non-computer scientist, could write a fast Scheme quickly if I could keep myself to a very small subset, so that’s not interesting to me.
  - eatonphil 4y ago
    Conformant is a word you introduced, they didn't say that.
pjmlp 4y ago
Only if they aren't attending degrees where compiler design is part of the curriculum, which if that is the case kind of speaks for the quality of the institution.
- mrtranscendence 4y ago
  A reasonably complete, fast language implementation, from scratch, in one weekend, though? By someone who was only introduced to compilers within the last few months? I don’t believe most students would be capable of that, but I’m not a computer scientist so what do I know.
  - pjmlp 4y ago
    Yes, Scheme is quite simple, no one is speaking about doing R7RS. Compared with current state of affairs in CPython, even with basic code generation algorithms, the machine code would be fast enough. Introducing to compilers means also writing one in the process, unless it is a lousy degree.

munificent 4y ago

Sure, but that's because Python has objects. If your write an object system on top of your performant hobby Scheme implementation, you'll likely find that the performance of its method dispatch is about as slow as it is in Python. Probably even slower. Purely procedural Python code isn't as slow as object-oriented Python code.

peatmoss 4y ago
That's fair, but also the fact that we're comparing hobby scheme implementations to two mainstream extremely popular implementations of Python and setting up conditions that forces (hobby) Scheme to play to Python's relative strengths is telling. :-) The Python ecosystem has certainly received a lot of developer resources and attention the past couple of decades. Shall we compare the performance of CLOS on SBCL, which again has seen comparatively little developer resources, to Python's performance in dealing with objects? I'd take that performance wager.
- Spivak 4y ago
  This isn’t as much of a gotcha as you think. Python is slow because the language is so dynamic and simply has to do more behind the scenes work on each line. It’s not impressive that a language that does less is faster. What’s impressive is that a language that does more, like JS on V8, is faster.
  - CraigJPerry 4y ago
    Is CLOS doing less than Python? I'm thinking CLOS has more dynamism than Python - they're both dynamically typed, they're both doing a lookup then dispatch, but then CLOS adds dynamism on top of that, it's also looking in the metadata thingy (i'm not a lisp developer, do they call it the hash? I'm meaning the key value store on every "atom" - i'm so out of my depth here, is atom the right word?) plus if i remember right the way CLOS works you use multiple dispatch not just single dispatch like python.
  - ByteJockey 4y ago
    The CLOS is more dynamic than python. You can do things like specialize a method on multiple types based on the runtime types (that is to say, the method conceptually belongs to the intersection of the classes, not any single class). I like python (especially things like comprehensions), but to say it's more dynamic than common lisp is a little insane.