fix partial_inner #1384

Job	Run time
macos-latest: clang++ Release Threads	30m 42s
macos-latest: clang++ Release OneTBB	3m 11s
macos-latest: clang++ Release PaRSEC	5m 34s
ubuntu-20.04: /usr/bin/g++-9 Release Threads	46m 52s
ubuntu-20.04: /usr/bin/g++-9 Release OneTBB	2m 35s
ubuntu-20.04: /usr/bin/g++-9 Release PaRSEC	3m 20s
macos-latest: clang++ Debug Threads	31m 3s
macos-latest: clang++ Debug OneTBB	3m 51s
macos-latest: clang++ Debug PaRSEC	5m 17s
ubuntu-20.04: /usr/bin/g++-9 Debug Threads	1h 1m 18s
ubuntu-20.04: /usr/bin/g++-9 Debug OneTBB	2m 54s
ubuntu-20.04: /usr/bin/g++-9 Debug PaRSEC	2m 48s
	3h 19m 25s

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