> Is compositing different bitmaps an embarrassingly parallel problem?
If you can make an initial approximate guess of the area for each section, you can split regions with lower and upper size constraints that can be laid out in parallel. A global branch and bound algorithm can coordinate those processes, tightening the upper constraints of one region when another connected region exceededs its minimum bounds.
Indeed there still may be degenerate cases where multiple regions need to be recalculated several times, but overall the default case should be able to finish without much conflict.
If you can make an initial approximate guess of the area for each section, you can split regions with lower and upper size constraints that can be laid out in parallel. A global branch and bound algorithm can coordinate those processes, tightening the upper constraints of one region when another connected region exceededs its minimum bounds.
Indeed there still may be degenerate cases where multiple regions need to be recalculated several times, but overall the default case should be able to finish without much conflict.