Improve the `DiscreteFactorFromErrors` #3085

Job	Run time
ubuntu-clang-deprecated Debug	22m 12s
ubuntu-clang-deprecated Release	22m 49s
ubuntu-clang-quaternions Debug	21m 57s
ubuntu-clang-quaternions Release	22m 50s
ubuntu-clang-tbb Debug	23m 6s
ubuntu-clang-tbb Release	23m 7s
ubuntu-clang-cayleymap Debug	21m 21s
ubuntu-clang-cayleymap Release	23m 7s
ubuntu-clang-system-libs Debug	21m 15s
ubuntu-clang-system-libs Release	22m 38s
ubuntu-no-boost Debug	22m 42s
ubuntu-no-boost Release	22m 48s
ubuntu-no-unstable Debug	17m 38s
ubuntu-no-unstable Release	18m 41s
	5h 6m 11s

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