`-par` command line option, script threads reporting off-by-one? #7799

This message is wrong, it reports one thread too many:

2016-04-03 12:37:54 Using 4 threads for script verification

The appropriate code is:

    LogPrintf("Using %u threads for script verification\n", nScriptCheckThreads);
    if (nScriptCheckThreads) {
        for (int i=0; i<nScriptCheckThreads-1; i++)
            threadGroup.create_thread(&ThreadScriptCheck);
    }

Also -par directly sets nScriptCheckThreads,

nScriptCheckThreads = GetArg("-par", DEFAULT_SCRIPTCHECK_THREADS);

so this means the option help is also incorrect:

  -par=<n>
       Set the number of script verification threads

What is the desired, expected behavior here?

(or is the thread that dispatches the work to script threads also counted as a 'verification' thread? we probably should document this, then, I spent some time on a wild goose chase for a missing ghost thread in htop)

Yes, it's counting the message processing thread as well, as it switches to signature validation once all to-be-checked ssignatures are pushed to the validation queue.

That's why -par=1 is consistent with "no parallellism".

Do you think there is a better way to report this?

That's why -par=1 is consistent with "no parallellism".

Sure, but I thought that was a special case where all validation was done in the main thread. As soon as there are threads, I thought no validation work was done anymore in the main thread. Apparantly I was wrong.

No, I think this is fine, closing.