Pygame simple loop runs very slowly on Mac

Question

E: After testing the same on OS X and Linux, I can confirm that the following only happens on OS X. On Linux it literally runs at a thousand fps, as I happened to wonder. Any explanation? I would much prefer developing on Mac, thanks to TextMate.

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Here's a simple loop that does almost nothing, and still runs very slowly. Can anyone explain why? FPS averages at little over 30, it takes a little over 30ms for each pass over the loop. Window size does not seem to affect this at all, as even setting a tiny window size like (50,50) has the same fps.

I find this weird, I would expect that any contemporary hardware could do a thousand fps for such a simple loop, even when we update every pixel every time. From the profile I can see that {built-in method get} and {built-in method update} combined seem to take around 30ms of time per call, is that really the best we can get out without using dirty rects?

pygame.init()
clock = pygame.time.Clock()
fps = 1000
#milliseconds from last frame
new_time, old_time = None, None    

done = False

while not done:

    clock.tick(fps)

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True

    # show fps and milliseconds
    if new_time:
        old_time = new_time
    new_time = pygame.time.get_ticks()
    if new_time and old_time:
        pygame.display.set_caption("fps: " + str(int(clock.get_fps())) + " ms: " + str(new_time-old_time))

    pygame.display.update()

Here's the beginning of a cProfile of the main function.

         94503 function calls (92211 primitive calls) in 21.011 seconds

   Ordered by: cumulative time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.026    0.026   21.011   21.011 new_main.py:34(main)
      652   14.048    0.022   14.048    0.022 {built-in method get}
      652    5.864    0.009    5.864    0.009 {built-in method update}
        1    0.444    0.444    0.634    0.634 {built-in method init}
      651    0.278    0.000    0.278    0.000 {built-in method set_caption}
     72/1    0.000    0.000    0.151    0.151 <frozen importlib._bootstrap>:2234(_find_and_load)
     72/1    0.000    0.000    0.151    0.151 <frozen importlib._bootstrap>:2207(_find_and_load_unlocked)
     71/1    0.000    0.000    0.151    0.151 <frozen importlib._bootstrap>:1186(_load_unlocked)
     46/1    0.000    0.000    0.151    0.151 <frozen importlib._bootstrap>:1122(_exec)
     46/1    0.000    0.000    0.151    0.151 <frozen importlib._bootstrap>:1465(exec_module)
     74/1    0.000    0.000    0.151    0.151 <frozen importlib._bootstrap>:313(_call_with_frames_removed)
     54/1    0.004    0.000    0.151    0.151 {built-in method exec}
        1    0.000    0.000    0.151    0.151 macosx.py:1(<module>)
        1    0.000    0.000    0.150    0.150 pkgdata.py:18(<module>)
     25/3    0.000    0.000    0.122    0.041 <frozen importlib._bootstrap>:1156(_load_backward_compatible)
      8/1    0.026    0.003    0.121    0.121 {method 'load_module' of 'zipimport.zipimporter' objects}
        1    0.000    0.000    0.101    0.101 __init__.py:15(<module>)
        1    0.000    0.000    0.079    0.079 config_reader.py:115(build_from_config)
        2    0.000    0.000    0.056    0.028 common.py:43(reset_screen)
        2    0.055    0.027    0.055    0.027 {built-in method set_mode}
    72/71    0.001    0.000    0.045    0.001 <frozen importlib._bootstrap>:2147(_find_spec)
    70/69    0.000    0.000    0.043    0.001 <frozen importlib._bootstrap>:1934(find_spec)
    70/69    0.001    0.000    0.043    0.001 <frozen importlib._bootstrap>:1902(_get_spec)
       92    0.041    0.000    0.041    0.000 {built-in method load_extended}
        6    0.000    0.000    0.041    0.007 new_map.py:74(add_character)
        6    0.000    0.000    0.041    0.007 new_character.py:32(added_to_map)
        6    0.001    0.000    0.041    0.007 new_character.py:265(__init__)
        1    0.000    0.000    0.038    0.038 macosx.py:14(Video_AutoInit)
        1    0.038    0.038    0.038    0.038 {built-in method InstallNSApplication}
        1    0.036    0.036    0.036    0.036 {built-in method quit}
       65    0.001    0.000    0.036    0.001 re.py:277(_compile)
       49    0.000    0.000    0.036    0.001 re.py:221(compile)

Answer 1

The answer to this ended up being that the retina display under OS X is the differentiating factor. Running it even on an external display on the same Mac works fine. But moving the window to the retina display makes it sluggish. With or without an external monitor connected.

On the other hand, it runs just fine on the same retina display under Linux. It is unclear what the difference in the display managers / rendering is that causes this, but I doubt there is anything one could do about it.