But replacing every character of every line is ... let's just say extremely unrealistic for now. So let's see what happens when we use what is only a very slightly more realistic dataset with a 50% duty cycle:

The work units are indeed quite small (1.0ms). But why then did you go and make the work units even smaller (0.5ms)?

But, and here is the real point. Never in any of these tests, yours or mine, your dataset or mine, have any of us found a threads & queues solution that achieves a performance gain. And anything less than faster is a failure. Simply not worth the effort.

Am I misreading your results? I see

• Not threaded = 23s
• T=1 = 25s
• T=2 = 13s
• T=3 = 10s
• T=4 = 9s

Huge gains except for a small penalty for T=1.