[Rcpp-devel] mixing R's and C++'s RNGs and distributions

[Matt D.]

On 6/24/2015 15:07, Ramon Diaz-Uriarte wrote:
> Hi Matt,
>
> Thanks a lot for the details and the work. That is great! There is a
> problem, though: in my particular case, I am uploading my package to
> BioConcutor, and there the compiler for Win is 4.6.3 so I am restricted to
> that. Including randutils will lead to an error during building the package
> in Windows.
Yeah, in this case I think replacing the source of entropy with 
something else may be the compromise choice (it's a range eventually 
passed to `mix_entropy`, so I'd investigate the effects on that).
That all being in the meantime / while waiting for the toolchain to 
catch up, of course...

Best,

Matt
>
> Best,
>
> R.
>
> On Wed, 24-06-2015, at 14:55, Matt D. <matdzb at gmail.com> wrote:
>> On 6/22/2015 12:31, Ramon Diaz-Uriarte wrote:
>>> Actually, I just noticed that things will not work if you need your package
>>> to run on Windoze: Rtools uses gcc 4.6.3 there, and this will not work with
>>> gcc 4.6 (neither in Linux nor Windows) with flag -std=c++0x or
>>> -std=gnu++0x. I guess this should be fixable, but I do not know enough to
>>> do it.
>> Hi again!
>>
>> I've just tried with the work-in-progress, _experimental_ version
>> available at the following location:
>> https://rawgit.com/kevinushey/RToolsToolchainUpdate/master/mingwnotes.html
>>
>> // In particular, I've used "Windows native compiler for 64 bit Windows
>> output mingw32mingw64_gcc-4.9.2.toolchain.tar.gz".
>>
>> This works better -- the only missing part is <thread> support :-(
>> However, it is not exactly essential here, in that it's used solely in
>> one place -- to get some extra entropy; that's all.
>> After temporarily removing dependence on `std::this_thread::get_id()`,
>> the example -- available at
>> http://www.pcg-random.org/posts/ease-of-use-without-loss-of-power.html
>> -- compiles and runs successfully.
>>
>> Incidentally,  one can get threads support for MinGW using MSYS2, which
>> gives:
>> Thread model: posix
>> gcc version 4.9.2 (Rev5, Built by MSYS2 project)
>>
>> However, the MinGW that comes with Rtools uses the following:
>> Thread model: win32
>> gcc version 4.9.2 (GCC)
>>
>> I presume there must be a reason for that. There are certainly
>> trade-offs present:
>> https://wiki.qt.io/MinGW-64-bit#GCC_Threading_model_.28posix_vs_win32.29
>> What hits us here is the "no C++11 <thread>, <mutex>, or <future> "
>> ("C11" appears to be a typo) part for the win32 choice.
>> // See also:
>> https://stackoverflow.com/questions/17242516/mingw-w64-threads-posix-vs-win32
>>
>> Note that there's nothing multithreading-specific about the library, so
>> even though I've also tested it with
>> https://github.com/meganz/mingw-std-threads (warning: just something
>> I've ran across while searching for multithreading support for MinGW
>> built w/ win32 threading model, quality and license unknown) and also
>> made it compile & work after a small patch (adding the std::hash
>> specialization), it's probably possible to use another source of entropy
>> here.
>>
>> I presume another idea would be to use a different GCC version, but
>> that's rather tedious --
>> https://stackoverflow.com/questions/25455829/using-a-different-gcc-version-from-that-included-with-rtools-with-rcpp-on-window
>> Other than the above, I'm wondering myself what's the "official"
>> recommendation for the C++11 threading support w/ Rcpp on Windows.
>>
>> Best,
>>
>> Matt