Tighten the density convergence #1561

Job	Run time
macos-latest: clang++ Release Threads	28m 1s
macos-latest: clang++ Release OneTBB	2m 0s
macos-latest: clang++ Release PaRSEC	6m 20s
ubuntu-20.04: /usr/bin/g++-9 Release Threads	50m 30s
ubuntu-20.04: /usr/bin/g++-9 Release OneTBB	1m 42s
ubuntu-20.04: /usr/bin/g++-9 Release PaRSEC	3m 19s
macos-latest: clang++ Debug Threads	24m 8s
macos-latest: clang++ Debug OneTBB	4m 7s
macos-latest: clang++ Debug PaRSEC	6h 0m 16s
ubuntu-20.04: /usr/bin/g++-9 Debug Threads	51m 4s
ubuntu-20.04: /usr/bin/g++-9 Debug OneTBB	1m 1s
ubuntu-20.04: /usr/bin/g++-9 Debug PaRSEC	1m 53s
	8h 54m 21s

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