Let me see... my crystal ball tells me that you are doing too much calculation to create your "gui in qt" and you should either find a way to 1) simplify the calculation, 2) do the calculation in the background and not while painting the plot, 3) give the user some feedback that tells them the progress of the calculation, or 4) do something else.

Alternatively, you could get someone to make you a special clock where the second hand takes 9 seconds to move a one second interval.