MatrixRef::lbegin() fails to compile

[devreal]

Consider the following code snippet:

dash::NArray<int, 2> matrix(dash::size(), N);
int *my_row = matrix[dash::myid()].lbegin();

which gives the following compiler error:

/home/joseph/opt/dash-0.3.0//include/dash/matrix/internal/MatrixRef-inl.h: In instantiation of ‘T* dash::MatrixRef<T, NumDimensions, CUR, PatternT>::lbegin() [with ElementT = int; int NumDimensions = 2; int NumViewDim = 1; PatternT = dash::BlockPattern<2, (dash::MemArrange)1u, long int>]’:
isx.cc:277:63:   required from here
/home/joseph/opt/dash-0.3.0//include/dash/matrix/internal/MatrixRef-inl.h:269:28: error: cannot convert ‘dash::LocalMatrixRef<int, 2, 2, dash::BlockPattern<2, (dash::MemArrange)1u, long int> >::iterator {aka dash::GlobViewIter<int, dash::BlockPattern<2, (dash::MemArrange)1u, long int>, dash::GlobStaticMem<int, dash::allocator::SymmetricAllocator<int> >, dash::GlobPtr<int, dash::GlobStaticMem<int, dash::allocator::SymmetricAllocator<int> > >, dash::GlobRef<int> >}’ to ‘int*’ in return
   return sub_local().begin();

As a workaround, I can probably use matrix.lbegin() for now.

[ddiefenthaler]

I'm surprised this one is left unanswered so long.

I tried to look into this yesterday and wanted to report my findings. In short this TODO has to be done: MatrixRef.h#L47-L49

To check this use case in a unit test it is possible to extend the existing case MatrixTest.MatrixLBegin:

   EXPECT_EQ_U(myid, static_cast<int>(*(matrix.lbegin())));
+  EXPECT_EQ_U(myid, static_cast<int>(*(matrix[myid].lbegin())));
   EXPECT_EQ_U(myid, static_cast<int>(*(matrix.local.block(0).begin())));
   EXPECT_EQ_U(myid, static_cast<int>(*(matrix.local.begin())));

First of all the type of lbegin() in MatrixRef can't be right. Instead local_type::iterator should be used. See MatrixRef.h#L199. If ElementT * is really sufficient that should be changed in LocalMatrixRef. See LocalMatrixRef.h#L93.

Next the typedef of local_type does not respect the current dimension in the MatrixRef. See the typedefs of local_type, local_reference_type, ... in MatrixRef.h#L105-L117. Shouldn't be this LocalMatrixRef<ElementT, NumDimensions, NumViewDim, PatternT> instead?

Last but not least the function sub_local() of MatrixRef is currently not supported. It tries to call this currently deactivated constructor of LocalMatrixRef: LocalMatrixRef-inl.h#L43-L64 That constructor contains this lines:

  DASH_THROW(
    dash::exception::NotImplemented,
    "Matrix view projection order matrix.sub().local() "
    "is not supported, yet. Use matrix.local().sub().");

As I'm not entirely sure how Matrix, MatrixRef, MatrixRefView, and so on works, I stopped there before breaking something completely.

@fuchsto Perhaps this is something for your view expressions.

[ddiefenthaler]

I spoke to soon, there is PR #428 which is handling at this issue. Perhaps my report is helpful anyways...

[rkowalewski]

@ddiefenthaler maybe something you can fix based on the already existing pull request and your breakdown? It would be nice to have it in the 0.3.0 release.

[devreal]

Ping. Just ran into this again :(