Feature/multitype arithmetic

I added some code to deal with matrices of type MultiTypeBlockMatrix. I am not quite convinced that the way in which I extended the traits are the best way to go. In particular, the isStatic is ambiguous, because actually all other matrices but BCRS are static as well, but do not work well with my implementation. Therefore, I am happy about any kind of ideas for improvements.

The technology is there. I found a useful code basis in dune-solvers and I believe it is reasonable to migrate algorithm.hh to dune-matrix-vector. Only minor parts from dune-solvers arithmetic.hh are needed. The vast hybrid utility power is in dune-common now. All static/dynamic & sparse/dense-magic is handled therein.

assigned to @maxka

A better switch than isStatic could be isDense, which might allow to process all dense matrices through the Dune::Hybrid::forEach functionality and handle the other cases separately (*). I fail to set up a method that compiles for both, MultiTypeBlockMatrix and FieldMatrix, either because some hybrid utilities are still missing or I do not know how to apply the existing ones to full effect.

(*) Perhaps, this might require even more case switches.

added 6 commits

• fa6787d2 - Revert "Add addProduct method for static matrix (MultiTypeBlockMatrix)."
• 3d0af5d5 - Revert "Add traits for MultiTypeBlockMatrix."
• b3009429 - Add traits for MultiTypeBlockMatrix.
• 2e38ff75 - Import algorithm from dune-solvers.
• 58309c56 - Add sparseRangeFor support for MultiTypeBlockMatrices.
• 7d973149 - Use hybrid algorithms for addProduct operation.

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unmarked as a Work In Progress

added 12 commits

• c0d5f251 - 1 commit from branch master
• 72dd418b - Add traits for MultiTypeBlockMatrix.
• 69b98568 - Add addProduct test for MultiTypeBlockMatrix arithmetic.
• 0e3d1bf7 - Add addProduct method for static matrix (MultiTypeBlockMatrix).
• 82392773 - Revert "Add addProduct method for static matrix (MultiTypeBlockMatrix)."
• f339ad46 - Revert "Add traits for MultiTypeBlockMatrix."
• debfbf50 - Add traits for MultiTypeBlockMatrix.
• e97169f3 - Import algorithm from dune-solvers.
• 0f4c6573 - Add sparseRangeFor support for MultiTypeBlockMatrices.
• 191b881e - Use hybrid algorithms for addProduct operation.
• e1e42adb - Use hybrid utilities from dune-common.
• 40064bb1 - Rename method rangeForEach to sparseRangeFor.

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added 2 commits

• 0a6f8f73 - Rename method rangeForEach to sparseRangeFor.
• ba77b2ae - Fix: Use renamed function.

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added 1 commit

• 8ebd9949 - Fix: make compile.

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added 3 commits

• 8e85fe2c - Reorder declarations+definitions and add forward declarations for helper.
• 1a096c61 - Replace more code with hybrid functionality.
• 772d0253 - Remove BCRS workaround.

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added 1 commit

• caefd2af - Add more forward declarations.

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added 1 commit

• 71b9b6b3 - Try qualifying for 'older' compilers.

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added 2 commits

• 57d9e5a2 - Revert "Add more forward declarations."
• 0e1ad04c - Remove superfluous :: from qualifyer.

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I think I made reasonable advances here. Shoutouts to @pipping for his feedback, though it does not show up here.

As the branch now does more than its name suggests, I will rebase it next week and continue to merge it to master soon.

added 4 commits

• 1229712c - Add missing include; clean up
• 7dbffd80 - Consistent indentation
• ea8166b3 - Remove superfluous braces
• bdfb1220 - Use std::enable_if_t consistently

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added 1 commit

• 999f702c - Use default: enable_if_t<A,B=void>

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added 9 commits

• 50760d5a - Add addProduct test for MultiTypeBlockMatrix arithmetic.
• d9c8060e - Add traits for MultiTypeBlockMatrix.
• efe3ba56 - Add an improved algorithm header
• 277ecb9f - Use hybrid algorithms for addProduct operation.
• de316c97 - Reorder declarations+definitions and add forward declarations for helper.
• f7a65e41 - Replace more code with hybrid functionality.
• dc65d9df - Remove BCRS workaround.
• 62050346 - Remove superfluous braces
• 422673f5 - Use std::enable_if_t consistently

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added 8 commits

• e191a626 - Add traits for MultiTypeBlockMatrix.
• 03ccc931 - Add an improved algorithm header
• 85410206 - Use hybrid algorithms for addProduct operation.
• e252b305 - Reorder declarations+definitions and add forward declarations for helper.
• 7bb519c1 - Replace more code with hybrid functionality.
• 5ee0a804 - Remove BCRS workaround.
• 59e753f3 - Remove superfluous braces
• 35a71037 - Use std::enable_if_t consistently

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I believe this is now in a state where it can be merged.

added 9 commits

• 881d0299 - Add addProduct test for MultiTypeBlockMatrix arithmetic.
• c23b682b - Add traits for MultiTypeBlockMatrix.
• ff955a37 - Add an improved algorithm header
• 592b1f66 - Use hybrid algorithms for addProduct operation.
• 4fb6a818 - Reorder declarations+definitions and add forward declarations for helper.
• 98347ebd - Replace more code with hybrid functionality.
• e6dd8473 - Remove BCRS workaround.
• 6c6d1d62 - Remove superfluous braces
• daac8c49 - Use std::enable_if_t consistently

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Putting this here as an afterthought (not meant to block the merge):

It would be nice if IsMultiTypeBlockContainer was closer to the idea of duck typing: What features do we expect from such a container? What's the general interface we have in mind here?

I noticed while thinking about and replying to https://gitlab.dune-project.org/core/dune-common/issues/74 that this would also allow us to do away with the #include in algorithm.hh.

Note to self: isScalar has made it into dune-common by now, under the more fitting name IsNumber. I plan on putting this to use here, too; probably later today.

Update: done.