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[Marie Rognes <question105900@xxxxxxxxxxxxxxxxxxxxx>]

Question #105900 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/105900

Marie Rognes proposed the following answer:
Anders Logg wrote:
> On Wed, Mar 31, 2010 at 09:21:50AM -0000, Chris Richardson wrote:
>   
>> Question #105900 on DOLFIN changed:
>> https://answers.launchpad.net/dolfin/+question/105900
>>
>>     Status: Answered => Open
>>
>> Chris Richardson is still having a problem:
>>
>> I still don't really understand why you need the extra qualification in these statements. Surely, the boundary
>> would be equally well defined without the x[1] clauses. Why do I need to put in the x[1] range so exactly?
>>
>>
>>    left = x[0] < DOLFIN_EPS and (x[1] > DOLFIN_EPS
>>                                       and x[1] < 1.0 - DOLFIN_EPS)
>>     
>
> If you don't include x[1] here, you will include the points (0, 0) and
> (0, 1). That means those point will be in "left" and thus
>
>   return on_boundary and not (left or right)
>
> will return false for those points. I assume you want to include those
> points in a no-slip boundary condition or similar.
>
>   
>>         right = abs(x[0] - 1.0) < DOLFIN_EPS and (abs(x[1] - .5) > DOLFIN_EPS
>>                                                   and x[1] < 2.0 - DOLFIN_EPS)
>>     
>
> This looks strange. What does x[1] range mean here?
>
>   


I don't know -- I suggested

	right = abs(x[0] - 1.0) < DOLFIN_EPS and (abs(x[1] - .5) > DOLFIN_EPS
                                                  and x[1] < 1.5 - DOLFIN_EPS)


--
Marie

> --
> Anders
>
>
>   
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