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BUG: EDF 2655: Low performance of hexa to tetra splitting

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The whole procedure performance was almost O(n^2) due to insertion of for example 5 elements in a mesh with a free ID at the beginning. The second element is then inserted with a O(n) complexity.
The hexas are now removed after all tetra insertions, which guarantees a O(n) complexity for the whole procedure at a limited memory cost (transient additional cost of 1/5 of total memory occupation at the end).
This commit is contained in:
rnc 2013-07-19 16:01:27 +00:00
parent 1fa8c22987
commit 3f3beb8b95
1 changed files with 38 additions and 1 deletions
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39
src/SMESH/SMESH_MeshEditor.cxx
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@ -1899,6 +1899,20 @@ namespace
};
} // namespace
class TElemToDelete
{
public:
TElemToDelete(const SMDS_MeshElement* theElem, SMESHDS_SubMesh* theSubMesh)
{
elem = theElem;
subMesh = theSubMesh;
}
const SMDS_MeshElement* Elem() const {return elem;}
SMESHDS_SubMesh* Submesh() {return subMesh;}
const SMDS_MeshElement* elem;
SMESHDS_SubMesh* subMesh;
};
//=======================================================================
//function : SplitVolumesIntoTetra
//purpose : Split volume elements into tetrahedra.
@ -1924,6 +1938,7 @@ void SMESH_MeshEditor::SplitVolumesIntoTetra (const TIDSortedElemSet & theElems,
double bc[3];
TIDSortedElemSet::const_iterator elem = theElems.begin();
std::vector<TElemToDelete> elem_to_delete;
for ( ; elem != theElems.end(); ++elem )
{
if ( (*elem)->GetType() != SMDSAbs_Volume )
@ -2087,11 +2102,26 @@ void SMESH_MeshEditor::SplitVolumesIntoTetra (const TIDSortedElemSet & theElems,
}
ReplaceElemInGroups( face, triangles, GetMeshDS() );
GetMeshDS()->RemoveFreeElement( face, fSubMesh, /*fromGroups=*/false );
// TElemToDelete faceToDelete(face, fSubMesh);
// elem_to_delete.push_back(faceToDelete);
}
} // loop on volume faces to split them into triangles
GetMeshDS()->RemoveFreeElement( *elem, subMesh, /*fromGroups=*/false );
// GetMeshDS()->RemoveFreeElement( *elem, subMesh, /*fromGroups=*/false );
// rnc : don't delete the elem here because it results in a mesh with a free
// ID at the beginning of the ID list. The first tetra is then inserted in O(1)
// but the second one is inserted in O(n), then the whole procedure has almost a O(n^2)
// complexity. If all elements to remove are stored and removed after tetra creation
// we get a O(n) complexity for the whole procedure.
// The memory cost is at worst a 6*n*constant memory occupation (where n is the number of elements)
// before deletion of the hexas and then 5*n*constant instead of a maximum of 5*n*constant.
// So there is a transient 1/5*(memory occupation) additional cost.
// Store the elements to delete
TElemToDelete elemToDelete(*elem, subMesh);
elem_to_delete.push_back(elemToDelete);
if ( geomType == SMDSEntity_TriQuad_Hexa )
{
@ -2102,6 +2132,13 @@ void SMESH_MeshEditor::SplitVolumesIntoTetra (const TIDSortedElemSet & theElems,
}
} // loop on volumes to split
// Delete stored elements
std::vector<TElemToDelete>::iterator it;
for( it = elem_to_delete.begin(); it!= elem_to_delete.end(); it++)
{
GetMeshDS()->RemoveFreeElement( it->Elem(), it->Submesh(), /*fromGroups=*/false );
}
myLastCreatedNodes = newNodes;
myLastCreatedElems = newElems;
}