On macOS, you can use Instruments (part of XCode, but it can also be used as a
standalone app) to do time profiling.
On macOS Sierra or later, you can run it from the commandline using:
instruments -l 10000 -D output.trace -t "Time Profiler" /path/to/executable
args...
Run
(On older versions of macOS, the `iprofiler` command does the same thing,
though with different options; for those, see `iprofiler --help` or `man
iprofiler`. You can also run programs from the Instruments UI, but that is more
cumbersome to set up.)
The `-l` option is for the maximum number of seconds the program may run (after
that, it will be killed), the `-D` option specifies the output directory for
the trace, and the `-t` option allows you to choose what kind of analysis to
run.
Then `open output.trace` to be able to inspect the profile in the Instruments
UI. You can see a sample screenshot of the UI with the output from the original
code [here](https://i.imgur.com/zHMk2Gz.png). Don't forget to invert the call
tree in the UI (using the button at the bottom of the window), it gives you a
much more useful breakdown of where time is spent.
