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Subject: Re: [SG14] P1385
From: Bob Steagall (bob.steagall.cpp_at_[hidden])
Date: 2019-02-07 09:56:05

There is a strawman implementation of P1385R0 at
https://github.com/BobSteagall/wg21/tree/master/linear_algebra. This
is the place where Guy and I will be publishing our linear algebra
work as it evolves. You'll find directories with code, our papers,
and the minutes from the calls and meetings of the linear algebra SIG.

Speaking of evolution, there is a draft version of R1 in the papers
directory (this was the version we discussed on yesterday's call).
Guy and I are working to finalize R1 in time for the face-to-face SG14
in Kona.


On Thu, Feb 7, 2019 at 7:56 AM Thomas Cassimon
<thomas.cassimon_at_[hidden]> wrote:
> Hello everyone,
> I'm new here and trying to get involved in the standardisation process for C++.
> I noticed that P1385 is getting a lot of attention, so I took a look at it myself. I've also been working on an implementation which you can find at https://bitbucket.org/ThomasCassimon/p1385/src/master/
> (I haven't been able to find R1 of the paper, so anything I say is based on R0)
> My implementation is far from done, but I've completed the storage engines highlighted in R0. The repository also has a suite of tests written using Catch2.
> Here are the most important things I've noticed about R0:
> Some of the methods of matrix_transpose_engine seem weird for a non-owning transposed view (Take for example data(), the pointer returned by this method won't be transposed, right? Otherwise, the transpose engine needs to make a copy, transpose the data and return a pointer to the copied data, but then its not a view anymore, right?)
> dyn_matrix_engine doesn't seem to have a way to specify size (and/or capacity) at construct time.
> The memory layout for dyn_matrix_engine also needs to be discussed, I've found 2 options already, both with advantages and disadvantages. This image (https://bitbucket.org/ThomasCassimon/p1385/src/master/img/memory_layout.png) should clarify what I mean.
> I've also found the resize/reserve semantics for a 2D array to be far from trivial, they require some design decisions to be made, this is also something that needs to be addressed.
> Those are the major points I had about P1385, the code also contains todo's for a number of smaller things, feel free to browse, give feedback and discuss.
> Thomas
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