[Patches] [ python-Patches-734118 ] Threaded Python prevents meeting frame rate targets

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Patches item #734118, was opened at 2003-05-07 20:45
Message generated for change (Comment added) made by loewis
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Category: Tkinter
Group: Python 2.3
>Status: Closed
>Resolution: Accepted
Priority: 5
Submitted By: Greg Couch (gregcouch)
Assigned to: Nobody/Anonymous (nobody)
Summary: Threaded Python prevents meeting frame rate targets

Initial Comment:
The diffs were made against the CVS version 1.157 of
Python/Modules/_tkinter.c.  We are using similar diffs
with Python 2.2.2.

The problem is with the busy-wait interval in
_tkinter.c.  Our application wants to output at a 30hz
frame rate, but with a threaded Python, the frame rates
are a multiple of the 20 millisecond Sleep call, so on
a really fast machine either 50hz or 25h (47hz and 23hz
on my system).

Enclosed is a Python test program that demonstrates the
limitation.
If you install a patched version of _tkinter.c, the
program will get the right frame rate.

       - Greg Couch

aftertest.py:
------------
#
# Repeatedly register a Tcl "after" callback to see how
many calls
# per second are made with various delay times.
#

start_time = None
count = 0
delay_ms = 33   # milliseconds

def after_cb():

  f.after(delay_ms, after_cb)

  global count, start_time
  import time
  t = time.time()
  if start_time == None:
    start_time = t
    count = 0
    return

  count = count + 1
  elapsed_time = float(t - start_time)
  if elapsed_time >= 1:
    r = count / elapsed_time
    print 'After calls per second: %.1f' % r
    start_time = t
    count = 0

import Tkinter
if hasattr(Tkinter._tkinter, "setbusywaitinterval"):
        Tkinter._tkinter.setbusywaitinterval(0)
f = Tkinter.Frame()
f.after(delay_ms, after_cb)
f.mainloop()


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>Comment By: Martin v. Löwis (loewis)
Date: 2003-05-09 10:20

Message:
Logged In: YES 
user_id=21627

Thanks for the patch. Applied as

NEWS 1.760
_tkinter.c 1.158


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