gh-128150: improve performances of uuid.uuid* constructor functions.

[picnixz]

There are some points that can be addressed:

• We can drop some micro-optimizations to reduce the diff. Most of the time is taken by function calls and loading integers.

• HACL* MD5 is faster than OpenSSL MD5 so it's better to use the former. However, using _md5.md5 or from _md5 import md5 is a micro-optimization that can be dropped without affecting performances too much (see cff86e9 and 7095aa4) For consistency, we'll rely on OpenSSL-based implementation even if it's a bit slower.

• The rationale of expanding not 0 <= x < 1 << 128 into x < 0 or x > 0xffff_ffff_ffff_ffff_ffff_ffff_ffff_ffff is due to the non-equivalent bytecodes.
  Similar arguments apply to expanding not 0 <= x < (1 << C) into x < 0 or x > B where B is the hardcoded hexadecimal value of (1 << C) - 1.

  Bytecode comparisons (not useful, constant folding will make them similarly performant)

   1 LOAD_SMALL_INT 0
  LOAD_NAME 0 (x)
  SWAP 2
  COPY 2
  COMPARE_OP 42 (<=)
  COPY 1
  TO_BOOL
  POP_JUMP_IF_FALSE 9 (to L1)
  NOT_TAKEN
  POP_TOP
  LOAD_SMALL_INT 1
  LOAD_SMALL_INT 128
  BINARY_OP 3 (<<)
  COMPARE_OP 2 (<)
  JUMP_FORWARD 2 (to L2)
  L1: SWAP 2
  POP_TOP
  L2: TO_BOOL
  UNARY_NOT
  POP_TOP
  LOAD_CONST 0 (None)
  RETURN_VALUE
  

  versus

   1 LOAD_NAME 0 (x)
  LOAD_SMALL_INT 0
  COMPARE_OP 2 (<)
  COPY 1
  TO_BOOL
  POP_JUMP_IF_TRUE 8 (to L1)
  POP_TOP
  LOAD_NAME 0 (x)
  LOAD_CONST 0 (340282366920938463463374607431768211455)
  COMPARE_OP 132 (>)
  POP_TOP
  LOAD_CONST 1 (None)
  RETURN_VALUE
  L1: POP_TOP
  LOAD_CONST 1 (None)
  RETURN_VALUE
  

• Issue: Improve performances of uuid.* functions #128150

---

📚 Documentation preview 📚: https://cpython-previews--128151.org.readthedocs.build/

[eendebakpt]

The changes itself look good at first glance. On the other hand: if performance is really important, there there dedicated packages to calculate uuids (binding to rust or C) that are much faster.

One more idea to improve performance: add a dedicated constructor that skips the checks. For example add to UUID:

 @classmethod
def _from_int(cls, int, is_safe=SafeUUID.unknown):
v= cls.__new__(cls)
object.__setattr__(v, 'int', int)
object.__setattr__(v, 'is_safe', is_safe)
return v

Results in

%timeit UUID._from_int(123 )
%timeit UUID(int=123, version=None)
451 ns ± 15.7 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)
767 ns ± 41.2 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

(the UUID._from_int can be used from inside uuid4 for example)

[picnixz]

On the other hand: if performance is really important, there there dedicated packages to calculate uuids (binding to rust or C) that are much faster.

I also thought about expanding the C interface for the module but it would have been too complex as a first iteration. As for third-party packages, I do know about them but there might be slightly differences in which methods they use for the UUID (and this could be a stop for existing code, namely switching to another implementation).

One more idea to improve performance: add a dedicated constructor that skips the checks

I also had this idea but haven't tested it as a first iteration. I wanted to get some feedback (I feel that performance gains are fine but OTOH, the code is a bit uglier =/)

[picnixz]

Ok the benchmarks are not always very stable but I do see improvements sith the dedicated constructor. I need to go now but I'll try to see which version is the best and the most stable.

[picnixz]

So, we're now stable and consistent:

+----------------------------------------+---------+-----------------------+-----------------------+
| Benchmark | ref | new | opt |
+========================================+=========+=======================+=======================+
| uuid3(NAMESPACE_DNS, os.urandom(16)) | 1.13 us | 767 ns: 1.47x faster | 767 ns: 1.47x faster |
+----------------------------------------+---------+-----------------------+-----------------------+
| uuid3(NAMESPACE_DNS, os.urandom(1024)) | 2.05 us | 1.82 us: 1.13x faster | 1.78 us: 1.15x faster |
+----------------------------------------+---------+-----------------------+-----------------------+
| uuid4() | 1.15 us | 867 ns: 1.33x faster | 860 ns: 1.34x faster |
+----------------------------------------+---------+-----------------------+-----------------------+
| uuid5(NAMESPACE_DNS, os.urandom(16)) | 1.10 us | 810 ns: 1.35x faster | 778 ns: 1.41x faster |
+----------------------------------------+---------+-----------------------+-----------------------+
| uuid5(NAMESPACE_DNS, os.urandom(1024)) | 1.52 us | 1.22 us: 1.24x faster | 1.19 us: 1.27x faster |
+----------------------------------------+---------+-----------------------+-----------------------+
| uuid8() | 926 ns | 673 ns: 1.38x faster | 671 ns: 1.38x faster |
+----------------------------------------+---------+-----------------------+-----------------------+
| Geometric mean | (ref) | 1.21x faster | 1.22x faster |
+----------------------------------------+---------+-----------------------+-----------------------+
Benchmark hidden because not significant (3): uuid1(), uuid1(node, None), uuid1(None, clock_seq)

Strictly speaking, the uuid1() benchmarks can be considered significant but only if you consider a 4% improvement as significant, which I did not. I only kept improvements over 10%. The last column is the same as the second one (PGO, no LTO) but using python -OO (namely assertions are removed).

[eendebakpt]

Nice improvement overall! Personally I am not a fan of the lazy imports here, but I'll let someone else decide on that.

[picnixz]

The entire module has been written so to reduce import times but I understand. I'll adress your comments tomorrow and will also check if I can remove some unnecessary micro optimizations. Thank you!

[picnixz]

Not sure what happens but I'm seeing slow downs. How can I check that constant folding was done?

EDIT: I'll regenerate the benchmarks to be sure. Wait a bit.
EDIT 2: Nevermind the numbers align now and constant folding seems to correctly appear. My bad.

[picnixz]

Here are the final benchmarks:

+----------------------------------------+---------+-----------------------+
| Benchmark | ref | upd |
+========================================+=========+=======================+
| uuid1() | 2.24 us | 2.13 us: 1.05x faster |
+----------------------------------------+---------+-----------------------+
| uuid1(node, None) | 1.26 us | 1.17 us: 1.07x faster |
+----------------------------------------+---------+-----------------------+
| uuid1(None, clock_seq) | 1.19 us | 1.11 us: 1.07x faster |
+----------------------------------------+---------+-----------------------+
| uuid3(NAMESPACE_DNS, os.urandom(16)) | 1.17 us | 695 ns: 1.68x faster |
+----------------------------------------+---------+-----------------------+
| uuid3(NAMESPACE_DNS, os.urandom(1024)) | 2.08 us | 1.72 us: 1.21x faster |
+----------------------------------------+---------+-----------------------+
| uuid4() | 1.15 us | 883 ns: 1.30x faster |
+----------------------------------------+---------+-----------------------+
| uuid5(NAMESPACE_DNS, os.urandom(16)) | 1.14 us | 797 ns: 1.43x faster |
+----------------------------------------+---------+-----------------------+
| uuid5(NAMESPACE_DNS, os.urandom(1024)) | 1.55 us | 1.20 us: 1.29x faster |
+----------------------------------------+---------+-----------------------+
| uuid8() | 953 ns | 658 ns: 1.45x faster |
+----------------------------------------+---------+-----------------------+
| Geometric mean | (ref) | 1.27x faster |
+----------------------------------------+---------+-----------------------+

We are indeed faster. Note that with a manual constant folding, I also have the same numbers (I just regenerated everything from scratch). I think sometimes we have noise. I'll update the NEWS as well to reflect the latest numbers.

[picnixz]

Replacing hashlib.md5 instead of using fallback MD5 is as follows:

uuid3(NAMESPACE_DNS, os.urandom(16)): Mean +- std dev: 781 ns +- 10 ns
uuid3(NAMESPACE_DNS, os.urandom(1024)): Mean +- std dev: 1.74 us +- 0.02 us

On main it is:

uuid3(NAMESPACE_DNS, os.urandom(16)): Mean +- std dev: 1.11 us +- 0.03 us
uuid3(NAMESPACE_DNS, os.urandom(1024)): Mean +- std dev: 2.04 us +- 0.02 us

With fallback MD5, we're a bit faster for small lengths:

uuid3(NAMESPACE_DNS, os.urandom(16)): Mean +- std dev: 702 ns +- 17 ns
uuid3(NAMESPACE_DNS, os.urandom(1024)): Mean +- std dev: 1.75 us +- 0.02 us

I think I can live with hashlib.md5. Smaller diff and consistent implementaion. I'll update the PR and the numbers.

[encukou]

Since we're always bundling HACL* MD5 implementation, I wondered whether we could just use it. Or do you think users would prefer if we use hashlib explicitly (and OpenSSL when available)?

It's possible to build Python without HACL*, mainly for environments where cryptography is somehow regulated (i.e. the infamous FIPS mode).

It might be OK to use HACL* by default in hashlib, possibly making it a bit faster for everyone (who didn't opt out).

But UUID should, IMO, use the default. We agree on that, hit the green button :)

[picnixz]

It's possible to build Python without HACL*, mainly for environments where cryptography is somehow regulated (i.e. the infamous FIPS mode).

Ah, I think I forgot about this one because I was recently working on HMAC and I didn't give the possibility to avoid HMAC-MD5 for instance.

But UUID should, IMO, use the default. We agree on that, hit the green button :)

:)

[picnixz]

I've just updated the NEWS entry (we have 30% gain if we only focus on 3, 4, 5 and 8, and a 20% gain if we include the benchmarks of UUID1(), but since the NEWS entry does not talk about version 1 (performance are the same), we should report the correct numbers)