Merge pull request #1247 from maspypy/1233 #609

Job	Run time
generate (macos-latest, clang++) / generate	1m 45s
generate (ubuntu-latest, g++-12) / generate	1m 29s
generate (ubuntu-24.04, g++-13) / generate	1m 39s
generate (windows-latest, g++) / generate	3m 18s
	8m 11s

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