[Gmsh] Setting random seed in geo file
Christophe Geuzaine
cgeuzaine at ulg.ac.be
Tue Dec 9 23:12:17 CET 2014
Dear Serban,
Thanks for the patch - it's been integrated in SVN. Let us know if you find other similar problems!
Christophe
> On 09 Dec 2014, at 17:32, Serban Georgescu <Serban.Georgescu at uk.fujitsu.com> wrote:
>
> For reference, an update to the modifications below.
>
> MVertexLessThanNum should be used instead if MVertexLessThanLexicographic.
> For some reason that I do not understand, MVertexLessThanLexicographic leads to crashes in some cases.
>
> Serban
>
> From: gmsh [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] On Behalf Of Serban Georgescu
> Sent: 05 December 2014 12:40
> To: David Bernstein
> Cc: gmsh at geuz.org Geuzaine
> Subject: Re: [Gmsh] Setting random seed in geo file
>
> Hi,
>
> Actually I had the same problem and in the last few days I put some time into finding the reason why this happens.
> The random seeds are actually hard-coded, the reason for the lack of reproducibility comes from a few STL containers that store pointers and were left with the default ordering – which means that the order will be dependent on the pointer addresses – hence the lack of reproducibility.
>
> Here are the modifications that you need to make in order to have full reproducibility:
> Note that these are made with respect to the source code of Gmsh 2.8.5.
>
> Mesh/meshGFace.cpp à added ordering to the set
>
> 1080c1080
> < std::set<MVertex*, MVertexLessThanLexicographic> all_vertices, boundary;
> ---
> > std::set<MVertex*> all_vertices, boundary;
>
> 1155c1155
> < for(std::set<MVertex*, MVertexLessThanLexicographic>::iterator it = all_vertices.begin();
> ---
> > for(std::set<MVertex*>::iterator it = all_vertices.begin();
>
> 1173c1173
> < for(std::set<MVertex*, MVertexLessThanLexicographic>::iterator it = all_vertices.begin();
> ---
> > for(std::set<MVertex*>::iterator it = all_vertices.begin();
>
> ----------------
> Mesh/meshGFaceBDS.cpp à defined what happens when we have two identical values in the sort
>
> 482,489d481
> < bool edges_sort (std::pair<double, BDS_Edge*> a , std::pair<double, BDS_Edge*> b)
> < {
> < if (a.first == b.first)
> < return ((*a.second) < (*b.second));
> < else
> < return (a.first < b.first);
> < }
> <
> 505c497
> < std::sort(edges.begin(), edges.end(), edges_sort);
> ---
> > std::sort(edges.begin(), edges.end());
> 558c550
> < std::sort(edges.begin(), edges.end(), edges_sort);
> ---
> > std::sort(edges.begin(), edges.end());
>
>
> ----------------
> Mesh/meshGRegion.cpp à added ordering to the set
> 1417c1417
> < static void getAllBoundingVertices(GRegion *gr, std::set<MVertex*, MVertexLessThanLexicographic> &allBoundingVertices)
> ---
> > static void getAllBoundingVertices(GRegion *gr, std::set<MVertex*> &allBoundingVertices)
> 1440c1440
> < std::set<MVertex*, MVertexLessThanLexicographic> allBoundingVertices;
> ---
> > std::set<MVertex*> allBoundingVertices;
> 1443c1443
> < std::set<MVertex*, MVertexLessThanLexicographic>::iterator itv = allBoundingVertices.begin();
> ---
> > std::set<MVertex*>::iterator itv = allBoundingVertices.begin();
> 1673,1680d1672
> < struct GFaceOrderedByTag
> < {
> < bool operator() (const GFace* first, const GFace* second) const
> < {
> < return (first->tag() < second->tag());
> < }
> < };
> <
> 1713c1705
> < std::set<GFace*, GFaceOrderedByTag> mySet;
> ---
> > std::set<GFace*> mySet;
>
>
> ----------------
>
> That’s about it.
> It would be nice if these modifications could be added to the SVN version.
>
> Cheers,
> Serban
>
> From: gmsh [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] On Behalf Of David Bernstein
> Sent: 02 November 2014 00:45
> To: gmsh at geuz.org Geuzaine
> Subject: [Gmsh] Setting random seed in geo file
>
> Sorry, I missed this post back in May. What is the geo file command to set the global random number seed?
>
> Thanks,
> Dave
>
> Hello,
>
> This issue has been fixed in the last versions. What is the version you are using ?
>
> JFR
> Le 22 mai 2014 à 23:29, David Bernstein <david at terafrac.org> a écrit :
>
> > Hi Everyone, I’m using Gmsh as a backend mesh generator in a project and it’s been working very well so far. One issue that we’ve encountered is reproducing a problem from a given set of simulation input parameters because Gmsh produces a different mesh every time it’s run with the same input.
> >
> > I’ve looked through the documentation and have not been able to find a way to set a random number seed so that the same mesh is produced every time for a given input .geo file. If anyone knows a way to do this please let me know.
> >
> > Thanks,
> > Dave
>
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--
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine