Don't spawn a separate thread if there is only one input file

[jhurliman]

This patch changes the logic in main.cxx (for platforms where echoprint-codegen can spawn multiple threads) to only spawn threads when more than one file is being fingerprinted. This results in a significant speedup for a common use case where echoprint-codegen is ran once per input file.

[alnesbit]

A better location for this comment might be up by the #ifdef _WIN32 directive. It could also be that use_threads is false because the user is processing one file on a system which does, in fact, support threads.

[jhurliman]

The current patch properly handles the case where the system supports threads but only one file is being processed (tested on OSX Lion with a single input file), but that's a good point about combining the #ifdef _WIN32 statements together. I'll submit a new pull request when I get a moment.

[jhurliman]

I took another look at this patch and I didn't see another more obvious place for the use_threads variable. Putting it any earlier in the file means the count variable won't be initialized, breaking bool use_threads = (count > 1); for thread-supported platforms.

[alnesbit]

Oh, I meant just for the comment, not the variable itself. (So it should be a trivial modification..?)

[jhurliman]

Bumping this patch for consideration.

[alnesbit]

Thanks, @jhurliman! We're accepting this patch and it will be merged in.

[jhurliman]

Just checking on the status of this