Added script to make nmatrix-fftw gem compile on Windows (ruby -v: ru…

[preetpalS]

…by 2.5.0p0 (2017-12-25 revision 61468) [x64-mingw32]) using MSYS2 MINGW64 for testing purposes.

This pull request is to mainly get feedback (related to #600). It contains a manual fix (you have to run a shell script sh manual_fftw_compilation.sh in the root of the directory and it only works for the mingw64 ruby version installed using msys2 (pacman -S mingw-w64-x86_64-ruby) from the mingw64 command line) for the nmatrix-fftw gem to compile (all tests pass by the way). It is based on the second part of the feedback given in #600 (comment) by @larskanis.

The fix applied to nmatrix-fftw should work for nmatrix-lapacke and nmatrix-atlas (but I encountered installing the C/C++/Fortran dependencies for these on Windows) as they are affected by the same dynamic loading issues. These issues could be resolved if the C extension components of the nmatrix-fftw, nmatrix-lapacke and nmatrix-atlas gems did not rely on dynamically linking with the C extension component of nmatrix at runtime (is dynamic linking used for performance reasons?). I'm not aware of any other gem that relies on its C extension component dynamically linking with another gem's C extension's during runtime (an example of a gem that relies on this behaviour and works on Windows would be useful).

Also

nmatrix/lib/nmatrix/mkmf.rb

Lines 56 to 58 in 293e2fb

	if /cygwin|mingw/ =~ RUBY_PLATFORM
	CONFIG["DLDFLAGS"] << " --output-lib libnmatrix.a"
	end

doesn't seem to do anything (it was changed in #530). Was the nmatrix-fftw gem once tested on Windows (@mrkn)?

Also note that I had installed fftw with the command pacman -S mingw-w64-x86_64-fftw.

Proof that the test suite passes for nmatrix-fftw passes on Windows:

$ bundle exec rake spec nmatrix_plugins="fftw"
... Skip many lines....
If you need more of the backtrace for any of these deprecations to
identify where to make the necessary changes, you can configure
`config.raise_errors_for_deprecations!`, and it will turn the
deprecation warnings into errors, giving you the full backtrace.

60 deprecation warnings total

Finished in 32.7 seconds
1620 examples, 0 failures, 139 pending
C:/msys64/mingw64/bin/ruby.exe -S rspec spec/00_nmatrix_spec.rb spec/01_enum_spec.rb spec/02_slice_spec.rb spec/03_nmatrix_monkeys_spec.rb spec/blas_spec.rb spec/elementwise_spec.rb spec/homogeneous_spec.rb spec/io/fortran_format_spec.rb spec/io/harwell_boeing_spec.rb spec/io_spec.rb spec/lapack_core_spec.rb spec/math_spec.rb spec/nmatrix_yale_spec.rb spec/rspec_spec.rb spec/shortcuts_spec.rb spec/slice_set_spec.rb spec/stat_spec.rb
C:/msys64/mingw64/bin/ruby.exe -S rspec spec/00_nmatrix_spec.rb spec/01_enum_spec.rb spec/02_slice_spec.rb spec/03_nmatrix_monkeys_spec.rb spec/blas_spec.rb spec/elementwise_spec.rb spec/homogeneous_spec.rb spec/io/fortran_format_spec.rb spec/io/harwell_boeing_spec.rb spec/io_spec.rb spec/lapack_core_spec.rb spec/math_spec.rb spec/nmatrix_yale_spec.rb spec/plugins/fftw/fftw_spec.rb spec/rspec_spec.rb spec/shortcuts_spec.rb spec/slice_set_spec.rb spec/stat_spec.rb

$ ruby -v
ruby 2.5.0p0 (2017-12-25 revision 61468) [x64-mingw32]

[translunar]

You may need to find someone who actually uses Windows to give you some feedback on this. :/