plotting to explore derivative errors --- interesting! #1434

Job	Run time
macos-latest: clang++ Release Threads	2m 19s
macos-latest: clang++ Release OneTBB	2m 43s
macos-latest: clang++ Release PaRSEC	3m 1s
ubuntu-20.04: /usr/bin/g++-9 Release Threads	47s
ubuntu-20.04: /usr/bin/g++-9 Release OneTBB	1m 10s
ubuntu-20.04: /usr/bin/g++-9 Release PaRSEC	3m 14s
macos-latest: clang++ Debug Threads	2m 47s
macos-latest: clang++ Debug OneTBB	3m 0s
macos-latest: clang++ Debug PaRSEC	3m 25s
ubuntu-20.04: /usr/bin/g++-9 Debug Threads	45s
ubuntu-20.04: /usr/bin/g++-9 Debug OneTBB	1m 45s
ubuntu-20.04: /usr/bin/g++-9 Debug PaRSEC	3m 3s
	27m 59s

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