Part 3 - pow: remove pyethash C extension, always use pure Python ethash by ping-ke · Pull Request #973 · QuarkChain/pyquarkchain

ping-ke · 2026-03-15T11:30:14Z

Summary

pyethash is a C++ extension that is not compatible with Python 3.13. The pure Python implementation in ethereum.pow.ethash can serve as a replacement; however, directly removing pyethash caused a significant regression in synchronization performance (10–20× slower), making block sync impractically slow.

This PR:

Fixes the compatibility issue by removing pyethash
Introduces a 4-round optimization pipeline (R1–R4) to recover and exceed the original performance
Reduces sync time from 25.24s → 0.86s (~29× improvement vs old Python, faster than pyethash)

Problem

pyethash 0.1.27 crashes with segfault or floating point exception on Python 3.13 when calling hashimoto_light().

Removing pyethash and falling back to the existing pure Python implementation leads to:

Heavy overhead in hex encoding/decoding
Excessive Python object allocations in hot loops
Severe performance degradation in PoW and block synchronization

Root Cause

A bug in src/python/core.c of pyethash:

PyArg_ParseTuple uses "y#" format which writes Py_ssize_t (8 bytes on 64-bit) into int variables (4 bytes), causing stack corruption.

// core.c line 76-77 (pyethash 0.1.27)
int cache_size, header_size;  // BUG: should be Py_ssize_t
if (!PyArg_ParseTuple(args, "k" PY_STRING_FORMAT PY_STRING_FORMAT "K",
    &block_number, &cache_bytes, &cache_size, &header, &header_size, &nonce))

Solution

This PR removes pyethash entirely and replaces it with a progressively optimized Ethash implementation, eliminating Python bottlenecks in the PoW hot path while restoring (and exceeding) the original performance.

Optimization Strategy

To systematically eliminate bottlenecks, we applied four incremental optimization rounds, each targeting a different layer:

R1–R2 (Python-level optimizations)
Remove serialization overhead and reduce Python object allocations
R3 (Cython hot loop)
Move the hottest FNV mixing loop into C
R4 (Full C pipeline)
Eliminate Python overhead entirely in the PoW critical path (including Keccak)

See #976 for more detail

Result

Root Block Sync Time (end-to-end)

Syncing one root block with 144 miniblocks (maximum load)

impl	sync time	vs pyethash	vs old	speedup vs R2
pyethash	1.47 s	1×	~17×	—
old	25.24 s	~17×	1×	—
R1	12.38 s	~8.4×	~2.0×	—
R2	8.52 s	~5.8×	~3.0×	1×
R3	1.39 s	~0.95×	~18×	~6×
R4	0.86 s	~0.58×	~29×	~10×

Restores performance after removing pyethash
Achieves ~29× speedup vs original Python implementation
Achieves better performance than pyethash baseline

Test plan

Mining and PoW verification still pass in existing tests
No ImportError on Python 3.13
Benchmarks cover old / R1 / R2 / R3 / R4
Sync tested end-to-end with profiling and timing logs

pyethash is a C++ extension that is not compatible with Python 3.13. The pure Python implementation in ethereum.pow.ethash is sufficient. Remove the conditional import and always use the Python path, adding @lru_cache to get_cache_slow for the same performance benefit. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ethereum/pow/ethpow.py

ethereum/pow/tests/bench_hashimoto.py

Add comment explaining why pyethash C++ acceleration was removed (not supported on Python 3.13) with link to #976

ethereum/pow/ethpow.py

…arrays ethash_utils.py: - replace hex-based encode_int/decode_int with struct.pack/unpack for serialize_hash and deserialize_hash (~30x faster per call) - inline ethash_sha3_512/256 to skip intermediate list conversion (~5x faster on list input) - add ethash_sha3_512_np and ethash_sha3_256_np: numpy ndarray variants that accept bytes or ndarray and return uint32 ndarray, eliminating tolist()/ np.array() round-trips in the hot path - consolidate keccak implementation here; ethash.py no longer duplicates it ethash.py: - store cache as 2D numpy uint32 ndarray (shape n x 16) via _get_cache - use ethash_sha3_512_np/256_np throughout to keep data in ndarray form - vectorize the 16-element mix update in calc_dataset_item and hashimoto inner loop using numpy arithmetic instead of list(map(fnv, ...)) - scalar fnv for cache_index uses plain Python int to avoid numpy scalar overhead test_ethash.py: - add TestEthashUtils covering serialize_hash, deserialize_hash, fnv, ethash_sha3_512/256 directly against reference implementations Benchmark: hashimoto_light ~23% faster end-to-end vs pure Python baseline; serialize_hash/deserialize_hash ~30x faster individually

ethash_utils.py: - remove struct, _FMT_16I, _FMT_8I (only served deleted serialize/deserialize_hash) - remove fnv (only used in tests, not in production path) - remove ethash_sha3_512 list variant (replaced by numpy ndarray variant) - remove serialize_hash, deserialize_hash, hash_words, xor, serialize_cache, deserialize_cache and related aliases (all replaced by ndarray.tobytes/frombuffer) ethash.py: - mkcache: use ethash_sha3_256_np(...).tobytes() directly, drop serialize_hash - drop serialize_hash import (no longer needed) ethpow.py: - remove pyethash C-extension dead code paths (get_cache/hashimoto were always equal to get_cache_slow/hashimoto_slow after pyethash removal) - keep get_cache_slow/hashimoto_slow structure as fallback for future Cython ext test_ethash.py: - remove test cases for deleted functions (serialize_hash, deserialize_hash, fnv, ethash_sha3_256, ethash_sha3_512 list variant) - cache/dataset hex comparison uses ndarray.tobytes().hex() directly bench_before_after.py, bench_hashimoto_compare.py: - add old/mid/new three-way comparison - old implementations kept inline for regression reference - new side imports from current ethash module directly

…to old/R1/R2 format

…umpy ethash_cy.pyx: typed C loop replacing the 256-iteration FNV parent mixing in calc_dataset_item. ethash.py auto-imports when built, falls back to pure Python otherwise. bench_hashimoto_compare.py extended with R3 column.

… fallback test

- ethash.py: rewrite with numpy uint32 arrays (R2); add ETHASH_LIB env var to select python/cython/auto at runtime - ethash_cy.pyx: add mix_parents (R3), cy_calc_dataset_item and cy_hashimoto_light with C keccak (R4) - keccak_tiny.c/h: portable C Keccak implementation for Cython R4 - ethpow.py: use ETHASH_LIB-aware hashimoto_light; simplify check_pow/mine - setup.py: build Cython extension with keccak_tiny.c - old_ethash.py: extract original hex-based implementation as reference baseline - bench_hashimoto_compare.py: merge bench_before_after.py; add R3/R4 sections; import old impl from old_ethash.py - test_ethash.py: use old_ethash as baseline for cython correctness test - remove bench_before_after.py

ping-ke · 2026-04-09T09:53:44Z

Add Performance improvements and related tests/bench. See #976 for more infor.

ping-ke mentioned this pull request Mar 17, 2026

EthStorage Devs Meeting #169 Agenda ethstorage/pm#251

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ping-ke requested review from qizhou, qzhodl and syntrust March 17, 2026 06:44

ping-ke mentioned this pull request Mar 20, 2026

QKC/OP Devs Meeting #88 Agenda QuarkChain/pm#132

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qzhodl reviewed Mar 25, 2026

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add bench for hashimoto

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qzhodl mentioned this pull request Mar 27, 2026

QKC/OP Devs Meeting #89 Agenda QuarkChain/pm#133

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ping-ke added 2 commits March 30, 2026 23:22

add comment for pyethash removal in ethpow.py

1db9d53

Add comment explaining why pyethash C++ acceleration was removed (not supported on Python 3.13) with link to #976

resolve comment

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ping-ke requested a review from qzhodl March 31, 2026 02:24

ping-ke mentioned this pull request Mar 31, 2026

Part 1 - upgrade: update all dependencies for Python 3.13 compatibility #974

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QKC/OP Devs Meeting #90 Agenda QuarkChain/pm#134

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ping-ke added 2 commits April 3, 2026 18:04

resolve upgrade/ethash comment

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Merge branch 'master' into upgrade/ethash

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ping-ke changed the base branch from upgrade/py313-baseline to master April 5, 2026 02:37

ping-ke changed the base branch from master to upgrade/py313-baseline April 5, 2026 02:37

ping-ke requested a review from syntrust April 5, 2026 02:38

ping-ke added 7 commits April 9, 2026 15:42

rename ethash_sha3_512/256_np -> ethash_sha3_512/256; refactor bench …

a05bef0

…to old/R1/R2 format

bench_before_after: rename mid -> R1 consistently

e477a64

gitignore: add Cython generated .c and .pyd files

7897277

add Cython to requirements, update README install docs, add Cython vs…

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… fallback test

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Part 3 - pow: remove pyethash C extension, always use pure Python ethash#973

Part 3 - pow: remove pyethash C extension, always use pure Python ethash#973
ping-ke wants to merge 14 commits intoupgrade/py313-baselinefrom
upgrade/ethash

ping-ke commented Mar 15, 2026 •

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Summary

Problem

Root Cause

Solution

Optimization Strategy

Result

Root Block Sync Time (end-to-end)

Test plan

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ping-ke commented Apr 9, 2026

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ping-ke commented Mar 15, 2026 •

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