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<div class="moz-cite-prefix">Hi.<br>
1) The default behaviour of the GridFactory in ALUGrid is to
figure out all missing boundary segments<br>
but of course ones that have been added by the user are not
overwritten or something - only<br>
missing ones are added. So there is no problem when you ad all
of them - only additional <br>
computational cost because ALU has to figure out which
boundary segments are missing (if any).<br>
2) There is a non-standard method on the GridFactory:<br>
Grid *createGrid ( const bool addMissingBoundaries, const
std::string dgfName = "" );<br>
So you can call factory.createGrid(fals);<br>
if you are sure that all boundary segments (including the
process borders have been added).<br>
If all boundaries have been added this should lead to the
same final grid as under (1) but will be <br>
slightly more efficient - especially on large parallel
machines.<br>
Andreas<br>
<br>
On 14/10/14 08:28, Aleksejs Fomins wrote:<br>
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<blockquote cite="mid:543CD092.7000003@lspr.ch" type="cite">
<pre wrap="">Hey Martin,
I have just realized that it would be extremely convenient for me if I
forced the user to enter all boundarySegments to the
curvilinearGridFactory. The reason for that is that I need to keep track
of the curvature of the boundaries in the metagrid, and if AluGrid
decides to construct some extra boundaries it will be very hard to track
them later and interpolate over them.
Is it possible to explicitly tell alugrid gridfactory that all boundary
segments will be provided and it need not create any additional ones, or
will it be able to figure it out?
Regards,
Aleksejs
On 10/07/2014 10:41 AM, Martin Nolte wrote:
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<pre wrap="">Hi Aleksejs,
unfortunately, DUNE does not force you to insert all domain boundary
segments. Hence, you cannot distinguish process borders from domain
boundaries without actually matching them.
If you actually know all domain boundaries, you can use your simple
algorithm to detect the process borders and insert them by hand (with
the given method). That's what the method is provided for!
Internally, ALUGrid's grid factory will use exactly the same algorithm
to find all boundaries of the local grid that have not been inserted by
the user. To find out which of these are actually domain boundaries and
which ones are process borders, these are then gathered on all
processes. Each process then removes the _received_ set of boundaries
from his map. What remains are actually domain boundaries. Yeah, it is a
lot of work for a small interface deficiency ;-).
But: Are you really sure you need to know this?
Best,
Martin
On 10/07/2014 09:34 AM, Aleksejs Fomins wrote:
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<pre wrap="">Dear Dune,
I was thinking of calculating the process borders to pass to alugrid
constructor, and I do not understand why this operation requires global
communication as stated in the dune-alugrid paper.
I propose the algorithm (3D):
1) Make an std::set of faces (face = indices of all facial vertices
sorted in ascending order)
2) Go over all elements on this process
3) For all faces of each element, put face in the set
4) If the set already contains this face, remove face from set instead
of inserting it
5) Resulting set should contain only process borders and domain
boundaries
6) Subtract domain boundaries that were inserted using
insertBoundarySegment on this process.
No global communication, get interprocessor boundaries with complexity
O(N log N) where N is number of elements on the process.
Can somebody please hint me to what I am missing?
Best,
Aleksejs
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