Bad performance in xmap generation
Enrico noticed that the xmap generation in ICON (ICON<-->HAMOCC) took very long. After some investigation, he found out that the changing the ordering of the indices in the idxlists significantly improved it.
This is a reproducer for this issue: reproducer.f90
$ mpif90 reproducer.f90 -I ../../../bin/yaxt/include/ -L ../../../bin/yaxt/lib/ -lyaxt -lyaxt_c -o reproducer
$ mpirun -n 4 ./reproducer
xmap (bad): 0.98948631399999998
xmap (opt): 1.2026120000000473E-003