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Using nodescheduler, which provides you with 8 cores, to reserve a node and then manually running casa with either -n 8 or -n 9 produces images that are pixel identical to what you would get with a hand crafted cpuset of 8 cores on the same socket and using -n 8 or -n 9. In other words if you have been using nodescheduler to reserve nodes, I don't think your casa images are suspect.
? Test with 4 way parallelization whether 4-0, 0-4, 2-2, 1-3, 3-1 distribution impacts resulting image using -n 4
cpuset=0,2,4,6 produces an image different that cpuset=1,2,4,6.