[Discuss-gnuradio] profiling the waterfall

[David Carr]

I've spent some time profiling the waterfallsink code.  Currently its 
pretty abominably slow.  I'm using python's profile module to do the 
following.

For a given run:

total run time on cpu as reported by the command "time"
real    0m17.874s
user    0m16.364s
sys     0m0.883s

python profile module reported total run time:
8.06 sec (8.06 is 45% of 17.87)

Where does the rest of the time go?

Here's the 8.06 sec broken down:

set_data() 92%
   set_data_loop() 86%
       dc1.SetPen(dc1.SetPen(wx.Pen(colour, 1, wx.SOLID)) 51%
       dc1.SetBrush(wx.Brush(colour, wx.SOLID)) 28%
       dc1.DrawRectangle(x_pos*p_width, 0, p_width, 1) 7% 

The offending code (broken into parts for profiling)

def set_data_loop_draw(self, dc1, x_pos, p_width, value):
       colour = wx.Colour(value, value, value)
       dc1.SetPen(wx.Pen(colour, 1, wx.SOLID))
       dc1.SetBrush(wx.Brush(colour, wx.SOLID))
       dc1.DrawRectangle(x_pos*p_width, 0, p_width, 1)

   def set_data_loop(self, dc1, dB, d_max, p_width):
       for x_pos in range(0, d_max):
               value = int(dB[x_pos] * 1.5)
               if value > 255:
                   value = 255
               elif value < 0:
                   value = 0
               self.set_data_loop_draw(dc1, x_pos, p_width, value)
              

   def set_data (self, evt):
       data = evt.data
       dB = 20 * Numeric.log10 (abs(data) + 1e-8)
       l = len (dB)
      
       dc1 = wx.MemoryDC()
       dc1.SelectObject(self.bm)
       dc1.Blit(0,1,self.info.fft_size,300,dc1,0,0,wx.COPY,False,-1,-1)

       if self.info.input_is_real:
           d_max = l/2
           p_width = 2
       else:
           d_max = l
           p_width = 1

           self.set_data_loop(dc1, dB, d_max, p_width)
     
       self.DoDrawing (None)

Where do we go from here?  I should note that the loop is not actually 
that slow, its just gets iterates for every drawn pixel.  That 
translates to 18,432 calls to the loop itself in 8.06 seconds at 512 
iterations per call.  Ideally this loop could be eliminated if there 
were a way to plot a vector rather than each point individually.  That 
would be very nice indeed.

It would also be nice to know where the other 17 - 8.06 = ~9 seconds go 
that profiling doesn't account for...

-David Carr