extern_sort also does an output bounds query
extern_sort also does an output bounds query

This misled Ravi, who was using it as reference code.

psuriana/Halide,psuriana/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide