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Subject: Re: [SG14] P1385
From: Bob Steagall (bob.steagall.cpp_at_[hidden])
Date: 2019-02-10 16:28:14


Jay and Arthur,

Thanks for the feedback. Guy and I are working on an R1 for Kona
which addresses the issues A and B.

--Bob

On Sun, Feb 10, 2019 at 5:04 PM Jayesh Badwaik <badwaik.jayesh_at_[hidden]> wrote:
>
> On Sunday, 10 February 2019 22:17:13 CET Arthur O'Dwyer wrote:
> > I just took a quick look at the repo, where the important code seems to be
> > https://github.com/BobSteagall/wg21/blob/master/linear_algebra/code/alt_test
> > .cpp
> >
> > I think it would be useful to write some tests that
> > (A) verify that expressions are not only well-formed but also have the
> > correct results (e.g.
> > https://github.com/BobSteagall/wg21/blob/cb69e22fd0/linear_algebra/code/alt_
> > test.cpp#L31 should probably go on to static_assert(b001) or
> > static_assert(not b001) depending on your intent).
> > (B) verify that some compound expressions such as `M1 + (M2 * M3)` are
> > well-formed, and also that they have the correct results
> > (C) include benchmarks of speed, especially for interesting compound
> > expressions (I'm sure the authors of P1417R0 can give you some interesting
> > expressions which come up frequently in real applications)
> > (D) include benchmarks of memory usage, especially for interesting compound
> > expressions. This is particularly important IMHO because it'll force you to
> > "design for testability" in this area: if you can tell how much memory is
> > being used by materialized temporaries, then you can also tell me how to
> > use a std::pmr::memory_resource to supply memory to this library, and you
> > can tell me if some innocuous-looking expression is going to blow my stack
> > segment, and so on.
> >
> > More pie-in-the-sky-ish, I would recommend writing test templates in terms
> > of WhateverMatrix<T> and then instantiating those test templates with
> > T=double, T=ThinWrapperAroundDouble, and so on. (Testing with
> > ThinWrapperAroundDouble is my attempt to test the optimizability of the
> > actual library code, independent of any special-case specializations it
> > might have for the concrete type `double`.)
>
> Thanks for listing out all the things required. I agree with all the points
> here. I have been meaning to write a separate testable implementation of my
> own (much in the lines of what you said), just to make sure that the one could
> reasonably reproduce the code from the specs. But I haven't started on them
> yet.
>
> --
> Best
> Jayesh Badwaik
> https://jayeshbadwaik.github.io_______________________________________________
> SG14 mailing list
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