too many open files
Currently, autfilt keeps a map of filename -> output file descriptors in case a filename needs to be filled with multiple automata. But when creating many output with different filenames, we quickly runs out of file descriptors:
~/git/genem-exp2/bench-app1 % xzcat ltlcross-prods.hoa.xz| autfilt -o benchmarks/ltlcross-prod.%L.hoa
autfilt: cannot open 'benchmarks/ltlcross-prod.47190015.1-47198251.7.hoa': Too many open files
We should probably close after output, and reopen in append mode if needed. Maybe we can even look at the size of the map to decide if it's ok to keep the descriptor open.