New submission from Alexander Belopolsky <[email protected]>:
As Terry J. Reedy mentioned in his comment on issue 7061, turtle documentation
is lacking information on how speed "codes" 0-10 translate into actual turtle
speed.
Attached script measures the speed of the two primitive operations that form
the basis of turtle functionality at various speed settings. The results below
show highly irregular pattern. The columns are: the speed code, time to draw a
200 unit line, time to complete a 360 degrees turn and the ratio of the two
times.
0: 0.01 0.01 0.83
1: 1.04 2.05 0.51
2: 0.49 1.06 0.46
3: 0.30 0.72 0.42
4: 0.23 0.54 0.44
5: 0.17 0.44 0.38
6: 0.13 0.39 0.35
7: 0.08 0.32 0.26
8: 0.08 0.28 0.30
9: 0.10 0.27 0.37
10: 0.08 0.23 0.36
>From the source code, it appears that the on-screen speed is controlled by the
>number of animation steps while each step takes approximately time controlled
>by the "delay" setting that defaults to 10 milliseconds.
The number of steps is determined by somewhat peculiar computations. For a
rotation by angle of a degrees at speed setting s, the number of steps is
n = 2 + int(a / (3 * s))
and for drawing a line of length d,
n = 1 + int(d / (3 * 1.1**s * s))
I am not sure what was the reason for these choices, but I think it would be
better if numeric speed code had a more direct relationship to the apparent
speed.
----------
assignee: d...@python
components: Demos and Tools, Documentation
messages: 119334
nosy: belopolsky, d...@python, eric.araujo, georg.brandl, gregorlingl,
terry.reedy
priority: normal
severity: normal
status: open
title: Relationship between turtle speed setting and actual speed is not
documented
versions: Python 3.2
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<http://bugs.python.org/issue10170>
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