build

Add a 2D MPL_ALLREDUCE interface #89

Job	Run time
ci (Release, linux gnu-10)	8m 57s
ci (Release, linux clang-12)	9m 48s
ci (Release, linux nvhpc-21.9)	5m 35s
ci (Release, linux intel-classic)	5m 15s
ci (Release, macos)	27m 19s
ci (Debug, linux gnu-10)	7m 54s
ci (Debug, linux clang-12)	9m 7s
ci (Debug, linux nvhpc-21.9)	5m 33s
ci (Debug, linux intel-classic)	5m 43s
ci (Debug, macos)	27m 59s
	1h 53m 10s

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