factor: benchmark the numbers that stress factorization

[sylvestre]

Products of several primes of similar, moderate size are where a factorization regression shows up first: trial division finds nothing, Pollard's rho has to run for a while before it splits anything, and any O(n^(1/4)) fallback never finishes. The prime power is there because rho cannot split p^k at all, so a regression in the perfect-power check is a hang rather than a slowdown, and the Mersenne prime is all primality testing and no factoring.

Sample counts are capped so the group takes about fifteen seconds rather than several minutes.

should be improved by uutils/num-prime#114

[Copilot]

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[codspeed]

Merging this PR will regress 1 benchmark

⚡ 1 improved benchmark
❌ 1 regressed benchmark
🆕 12 new benchmarks
⏩ 430 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	factor_multiple_u64s[2]	68 ms	70.2 ms	-3.17%
⚡	Memory	factor_multiple_u64s[2]	90.8 KB	5.6 KB	×16
🆕	Simulation	a_1279_bit_prime	N/A	56.4 ms	N/A
🆕	Simulation	a_prime_to_the_seventh	N/A	721.3 µs	N/A
🆕	Simulation	five_38_bit_primes	N/A	1.6 s	N/A
🆕	Simulation	small_factors_and_a_large_prime	N/A	1.2 ms	N/A
🆕	Simulation	thirteen_39_bit_primes	N/A	9.7 s	N/A
🆕	Simulation	three_39_bit_primes	N/A	263.1 ms	N/A
🆕	Memory	a_1279_bit_prime	N/A	19.1 KB	N/A
🆕	Memory	a_prime_to_the_seventh	N/A	15 KB	N/A
🆕	Memory	five_38_bit_primes	N/A	22.1 KB	N/A
🆕	Memory	small_factors_and_a_large_prime	N/A	100.6 KB	N/A
🆕	Memory	thirteen_39_bit_primes	N/A	22.4 KB	N/A
🆕	Memory	three_39_bit_primes	N/A	13.6 KB	N/A

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing sylvestre:factor-bench (ae3e119) with main (0149247)²}

Footnotes

1. 430 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (240ce3b) during the generation of this report, so 0149247 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)