[metapost] arclength() tolerances

[Franck Pastor]

Le 3 avr. 2014 à 10:32, Taco Hoekwater <taco at elvenkind.com> a écrit :

> Hi Hartmut,
> 
> On 02 Apr 2014, at 21:10, Hartmut Henkel <hartmut_henkel at gmx.de> wrote:
> 
>> Hi,
>> 
>> in metapost there seem to be absolute tolerance values for iterative
>> algorithms like arclength() even in the double numbersystem:
> 
> Yes, the arc_test() routine (the core or arclength/arctime) uses a predefined 
> tolerance of unity/4096. While it is clear to me why it needs a tolerance
> setting, it is not clear why that precise value, nor does lowering it actually
> help, it just makes mp run slower:
> 
> With tolerance=1E-8:
> 
> 0.031477030364784685, 31415.995269569834
> real	0m1.606s
> user	0m1.601s
> sys	0m0.003s
> 
> With tolerance=1E-9:
> 
> 0.031477030364784685, 31415.995269569834
> 
> real	1m40.888s
> user	1m40.820s
> sys	0m0.034s
> 
> Maybe there is some intrinsic error in the approximation code? One of the
> more important reasons why I will quit developing metapost is that I do not 
> really understand any of this computational stuff, nor can I easily grasp the
> theory behind it when attempting to educate myself.
> 
> Best wishes,
> Taco
> 

:-( This is VERY bad news! MetaPost has improved a lot since you have begun to maintain it! I hope someone will be found who can take over your amazing job.

Best regards,

Franck Pastor (bedroefd)