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GeezerVison is showing github.com — gh-100239: specialize bytes binary operations by Wulian233 · Pull Request #149458 · python/cpython

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@Wulian233

@Wulian233 Wulian233 commented May 6, 2026 •
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The following was generated by Codex:

  • bytes[3]: 20,000,000 iterations
  • 7 repeats
  • PYTHON_UOPS_OPTIMIZE=0
  • compared normal specialization vs PYTHON_SPECIALIZATION_OFF=1

Results:

Benchmark Specialized median Unspecialized median Speedup
bytes[3] 0.513025s 0.701673s ~26.9% faster
Details 
import statistics
import time

N = 20_000_000
REPEAT = 7


def bench_bytes_index():
    b = b"foobar"
    x = 0
    for _ in range(N):
        x = b[3]
    return x


# Warm up for specialization.
for _ in range(5):
    bench_bytes_index()

samples = []
for _ in range(REPEAT):
    t0 = time.perf_counter()
    result = bench_bytes_index()
    samples.append(time.perf_counter() - t0)

print("result", result)
print("samples", " ".join(f"{s:.6f}" for s in samples))
print("median", f"{statistics.median(samples):.6f}")
  • Issue: Specialize long tail of binary operations using a table. #100239

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@Wulian233
pythongh-100239: specialize bytes binary operations
e0173f1
@bedevere-app bedevere-app Bot mentioned this pull request May 6, 2026
Specialize long tail of binary operations using a table. #100239
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@bedevere-app bedevere-app Bot added the awaiting review label May 6, 2026
eendebakpt
eendebakpt reviewed May 6, 2026
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Comment thread Python/specialize.c Resolved

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Comment thread Python/specialize.c Outdated
}

static PyObject *
bytes_slice_subscr(PyObject *lhs, PyObject *rhs)

@eendebakpt eendebakpt May 6, 2026

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The implementation here is seems copied from bytes_subscript (in byteobject.c) and still has a large overlap. Can you refactor the bytes_subscript into multiple methods so that the method here only becomes a very thin wrapper?

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StanFromIreland
StanFromIreland reviewed May 6, 2026
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Comment thread Python/specialize.c Resolved

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corona10
corona10 reviewed May 6, 2026
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I am not sure we actually need this specialization. Is there any metrics that that this operation is executed frequently in performance benchmark.
We can add tons of specialization it we want, but IIUC, we just pick few of them.

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@eendebakpt

eendebakpt commented May 7, 2026

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I am not sure we actually need this specialization. Is there any metrics that that this operation is executed frequently in performance benchmark. We can add tons of specialization it we want, but IIUC, we just pick few of them.

I agree we should limit the number of specializations. The bytes indexing seems worthwhile atm, the bytes slicing not so much.

Another option: reconsider an extension mechanism. It was implemented once and reverted (because of a python release date and some technical worries): #133395. If we can get similar performance improvements with the extension mechanism, when we can leave which ops to specialize to the user and outside cpython.
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@Wulian233
fix
c7dfa59
@read-the-docs-community

read-the-docs-community Bot commented May 7, 2026

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Documentation build overview

📚 cpython-previews | 🛠️ Build #32582538 | 📁 Comparing c7dfa59 against main (b3cfd36)

  🔍 Preview build  

26 files changed · ± 26 modified

± Modified

  • c-api/exceptions.html
  • c-api/index.html
  • c-api/interp-lifecycle.html
  • c-api/stable.html
  • c-api/threads.html
  • deprecations/index.html
  • deprecations/pending-removal-in-3.17.html
  • deprecations/pending-removal-in-3.19.html
  • howto/free-threading-extensions.html
  • howto/perf_profiling.html
  • and 16 more...
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@Wulian233 Wulian233 closed this May 24, 2026
@Wulian233
Wulian233 deleted the bytes branch May 24, 2026 07:47
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4 participants

@Wulian233 @eendebakpt @corona10 @StanFromIreland
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