Optimisations in adjacency matrix calculator #2964

Job	Run time
codecheck / codecheck	43m 37s
conda / conda (ubuntu-20.04)	11m 13s
docker / docker (fedora39)	1h 0m 25s
conda / conda (macos-12)	23m 7s
docker / docker (rocky8)	23m 26s
linux / linux (-doc-mpi-)	39m 26s
conda / conda (macos-14)	7m 14s
linux / linux (-mpi-)	49m 58s
mac / macports (macos-12)	17m 15s
linux / linux (-coverage-mpi-)	1h 0m 38s
mac / macports (macos-14)	10m 48s
linux / linux (-debug-)	29m 18s
mac / macports (+allmodules, macos-12)	20m 59s
mac / macsimple (macos-12)	8m 18s
linux / linux (-debug-mpi-)	42m 5s
mac / macsimple (macos-14)	5m 30s
linux / linux (-intel-)	44m 43s
linux / linux (-pycv-mpi-)	16m 58s
	8h 34m 58s

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