It seems like it doesn't answer it's own question, so I'll pose another.
The entire Lua core is 15kLoC. Is that more than or less than what's needed for python's "a + b", assuming a and b are defined.
I'm genuinely curious.
How many lines of C it takes to execute a + b in Python
51–60 of 224 posts
Re: How many lines of C it takes to execute a + b in Python
#52Earlier quoted context omitted.
It looks like you can disable the slower randomized hashing yourself by setting PYTHONHASHSEED to 0. Though I don't know if there's further speedup to be had by using a different hash implementation. https://docs.python.org/3/using/cmdline.html#envvar-PYTHONHA... The original issue: https://bugs.python.org/issue13703
That only disables the keying of the hash function (sets the initial value to 0), it does not change the hash function. The hashseed is a per-process value, it has basically no impact on performances.
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Re: How many lines of C it takes to execute a + b in Python
#53Lines of C aren't the defining factor. You want total instructions executed.
It’s about 100 for x86_64 https://www.computerenhance.com/p/waste
Re: How many lines of C it takes to execute a + b in Python
#54Earlier quoted context omitted.
It shoud've been possible to establish the lower and upper bounds.
it's about as possible as solving the halting problem if you allow for operator overloading.
Leaving aside the apparent confusion between C and C++, do you really imply overloading could make adding two fixed size numbers in Python take unbounded time?
Re: How many lines of C it takes to execute a + b in Python
#55Earlier quoted context omitted.
Python 3.11 appears to have switched to SipHash 1-3 for strings, from 2-4, following the lead of Rust and Ruby. https://github.com/python/cpython/issues/73596 However, Python does not use it for integers; >>> hash(10) 10 >>> hash(100) 100 >>> hash(2**61-2) == 2**61-2 True >>> hash(2**61-1) 0
That’s good though, right? Is there a reason for not using an identity hash (is that the right term?) for integers?
That depends on the hash table implementation and the distribution of the integers.
For the commonly used hash tables with prime size that use modulo to turn the hash code into a slot index, an identity hash for integers is usually fine (unless many integers are multiples of the prime size).
But other hash tables use power-of-two size to replace the modulo operation with a faster bit-and operation. Now an identity hash for integers is much more problematic, e.g. if all integers are multiples of 1000, only 1/8th of the table slots can be used.
The latter kind of hash tables would like all bits in the hash value to be well-distributed; and this is typically not true of the underlying integers. So an additional mixing operation needs to be used. Whether that mixing happens in the hash function or in the hash table depends on the implementation (for some, it's even configurable, e.g. is_avalanching marker in ankerl::unordered_dense).
Re: How many lines of C it takes to execute a + b in Python
#56Earlier quoted context omitted.
it's about as possible as solving the halting problem if you allow for operator overloading.
Leaving aside the apparent confusion between C and C++, do you really imply overloading could make adding two fixed size numbers in Python take unbounded time?
I'm saying a + b in Python can do whatever you override the __add__/__radd__ to. Not sure why you invoke C/C++ here.
If you only limit yourself to numbers (the title doesn't specify that) it should be bounded, but the article goes into some depth here, so I'll leave it at that.
Re: How many lines of C it takes to execute a + b in Python
#57Earlier quoted context omitted.
The semantic issues of making a performant Python language implementation are more or less exactly the same as for JS and Lua, optimizing Ruby seems to possibly have even more "magic" that needs patching but we've seen the Shopify team get cracking on that (it includes MaximeCB that did HiggsJS). PyPy is in many aspects to be rated as a research project that tried a novel approach to reduce the workload compared to t…
Unfortunately Python's innard is much more complicated than most expectations. You have named JS and Lua, but those languages never have "magic" methods---JS instead has prototypes and more recently proxies, while Lua has metatables. Ordinary objects aren't magic in this sense, and conversely magical objects are generally deliberate choices in those languages. But Python's magic `__dunder__` methods are everywhere in…
It’s not entirely true that JS does not have magic methods. `valueOf` and `toString` can show up surprisingly deep into the resolution of operations, and recent JS has “well known symbols” to implement or override behaviour.
However it is true that this is much, much less extensive than it is in Python. As of 3.12, section 3.3 (“special method names”) of the data model documentation lists 107 entries (although some of them only apply to class protocols, and a handful are duplicates for async versions / context of sone operations).
Re: How many lines of C it takes to execute a + b in Python
#58Sounds like it would be easier to just use C anyway.
Tell that your average data Joe and he will say "But C is a letter, not a programming language".
Re: How many lines of C it takes to execute a + b in Python
#59A while back someone posted their patch to cpython where they replaced the hash function with a fast one and claimed this dramatically sped up the whole Python runtime. They claimed that the hash function was used constantly —e.g. 11 times in print("hello world")—because it's used to look up object properties. Apparently the default implementation is not optimized for performance but for security, just in case the so…
This may be a somewhat uninformed opinion, but I think CPython is just straight up not particularly good software. There are a million and one optimizations that other major scripting runtimes (V8, LuaJIT, PyPy, Ruby YJit etc.) have had for years that CPython is lacking. This is by design though. CPython has never been focused on performance, that's why it's not even JIT. It optimizes for simplicity and easy interope…
The last couple of CPython versions have had dramatic speed improvements, so that demonstrates your point but also gives some hope that things are changing on that front.
Re: How many lines of C it takes to execute a + b in Python
#60Earlier quoted context omitted.
Leaving aside the apparent confusion between C and C++, do you really imply overloading could make adding two fixed size numbers in Python take unbounded time?
I'm saying a + b in Python can do whatever you override the __add__/__radd__ to. Not sure why you invoke C/C++ here. If you only limit yourself to numbers (the title doesn't specify that) it should be bounded, but the article goes into some depth here, so I'll leave it at that.
Fair!