[Insight-developers] Memory leaks in Mesh
Miller, James V (Research)
millerjv@crd.ge.com
Tue, 1 Oct 2002 15:00:34 -0400
I have a short term fix to the GetCellBoundaryFeature()
memory leak. If the feature is an implicit feature we could
skip putting it into the boundary feature vector. This avoids
the leak at the cost of having to recreate the boundary feature
every time it is used.
I think what we really want is to know whether an implicit feature
has already been "created" and return that previously created feature.
> -----Original Message-----
> From: Miller, James V (Research)
> Sent: Tuesday, October 01, 2002 2:27 PM
> To: 'Luis Ibanez'
> Cc: Insight-developers (E-mail)
> Subject: RE: [Insight-developers] Memory leaks in Mesh
>
>
> I don't think we want to remove any of this functionality. I
> just think
> we need to fix the items that are currently broken and
> perhaps reduce the
> complexity a bit. One question that is readily apparent is
> that because
> of the number of internal data structures in the mesh, it is
> very difficult
> to determine who owns what memory. There are vectors of raw points,
> there are vectors of SmartPointers, and then there are
> AutoPointers running
> around. So it is really unclear who is responsible for
> releasing memory.
>
> For instance, if I create a cell and pass it to the mesh. Do
> I release the
> memory for the cell or does the mesh ultimately release the
> memory. If I
> make a query on the mesh that returns some sort of "pointer",
> do I release the
> memory or does the mesh. I don't recall how these things
> operated when
> SmartPointers were used but the mixture of raw pointers and
> AutoPointers
> currently used make it hard to decipher.
>
> It would be nice to have this "resolved" before we
> cut the release.
>
> For the problem associated with GetCellBoundaryFeature()
> I am think of the following options:
>
> If the boundary feature is an implicit feature, then
>
> 1) create an explicit feature to add to the
> AssignedCellBoundary vector
>
> 2) create an explicit feature and add it to an
> "ImplicitAssignedCellBoundary"
> vector
>
> 3) have different a flag in the features that indicate
> whether they are
> explicit features of implicit features. I suppose this could
> be done with
> a flag or a type (subclass).
>
> option #2 would allow the mesh to keep track of what boundary features
> were assigned by the user and what boundary features were created on
> the fly. (option #3 may allow the same thing)
>
> Another thought that would simplify things is for the
> Mesh::SetBoundaryAssignment
> to not take a BoundaryIdentifier. It looks like the boundary
> assignments are held
> in a map that maps
>
> <CellIdentifier, FeatureIdentifier> to a BoundaryIdentifier
>
> So to make a boundary assignment, the user must know the cell
> they want to
> assign it to, the feature they want to assign it to, the
> dimension of the feature
> they want to assign it to AND they must know where they want
> that assignment to
> occur in the boundary feature vector. I have no problem with
> the (cell, feature,
> dimension) being needed. But it may simplify things if the
> user did not have
> to specify the boundary identifier.
>
> If someone wants a boundary feature, they query the assignment map
> to see if there is a BoundaryIdentifier associated with
> the <CellIdentifer, FeatureIdentifier> pair and then they look up
> the boundary feature using the returned BoundaryIdentifier in the
> boundary feature vector.
>
> Instead of using a map and a vector, we could just a map that directly
> converted the pair
>
> <CellIdentifier, FeatureIdentifier> to a BoundaryFeature
>
>
>
>
>
>
>
> > -----Original Message-----
> > From: Luis Ibanez [mailto:luis.ibanez@kitware.com]
> > Sent: Tuesday, October 01, 2002 1:57 PM
> > To: Miller, James V (Research)
> > Cc: Insight-developers (E-mail)
> > Subject: Re: [Insight-developers] Memory leaks in Mesh
> >
> >
> >
> > Hi Jim,
> >
> > It looks like the Mesh requires a major refactoring.
> >
> > There is a large set of functionalities provided by
> > the Mesh that don't seem to be used by the toolkit
> > but cost a lot on the implementation. For example
> > the management of neighborhood relationships
> > between cells and the policy of simulating explicit
> > cells. Most of the dificulties in memory managment
> > come from these features.
> >
> > How about having a discussion on the use/design
> > of the Mesh at next week meeting. Probably on
> > Tuesday ?
> >
> >
> > Luis
> >
> >
> > ======================================
> >
> > Miller, James V (Research) wrote:
> >
> > > I am trying to track down the memory leaks in the mesh class.
> > >
> > >
> > >
> > > It looks like Mesh::SetCell(CellIdentifier,
> CellAutoPointer&) leaks
> > > memory if there was already a cell assigned at the specified
> > > CellIdentifier location. The cells are ultimately kept in
> > a vector of
> > > pointers to cells (not SmartPointers, not AutoPointers). So,
> > > SetCell() just overwrites the location in the vector with a new
> > > pointer to a cell.
> > >
> > >
> > >
> > > This means the user of the Mesh has to manage the
> > de-allocation of the
> > > cell currently at the CellIdentifier position prior to calling
> > > SetCell(). This should be documented somewhere. I modified the
> > > itkMeshTest to do this deallocation.
> > >
> > >
> > >
> > > It also looks like Mesh::GetCellBoundaryFeature() leaks
> when it is
> > > asked for the same "implicit" boundary feature multiple
> > times. When
> > > asked for an implicit boundary feature, memory get
> > allocated to hold
> > > the feature (i.e. when asking for an edge of a triangle where the
> > > triangle is just specified with 3 vertices but no explicit
> > edges are
> > > defined). This created feature gets inserted into the vector of
> > > boundary features. When called a second time for the
> same implicit
> > > boundary feature, memory gets allocated for the feature and the
> > > feature overwrites the previously created boundary feature. This
> > > causes a leak. There is a check in the code that if the
> > cell boundary
> > > feature is one of the "assigned" boundary features (explicit
> > > features), then it simply returns the feature from the boundary
> > > feature vector. However, when a boundary feature is implicit, an
> > > object is created to be returned to the user and that
> > object is added
> > > to the vector of boundary features but that object is NOT
> > added to the
> > > list of ASSIGNED boundary features. So the check in the
> code fails
> > > and a new feature is allocated and overwrites the
> previous boundary
> > > feature pointer in the boundary feature vector. Once an implicit
> > > feature is queried, should it be converted (and recorded) as an
> > > explicit and assigned feature?
> > >
> > >
> > >
> > > * Jim Miller*
> > > */_____________________________________/*
> > > / Visualization & Computer Vision//
> > > /GE Research/
> > > /Bldg. KW, Room C218B/
> > > /P.O. Box 8, Schenectady NY 12301/
> > >
> > > //_ millerjv@research.ge.com <mailto:millerjv@research.ge.com> _/
> > >
> > > /_ james.miller@research.ge.com_/
> > > /(518) 387-4005, Dial Comm: 8*833-4005, /
> > > /Cell: (518) 505-7065, Fax: (518) 387-6981/
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
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