[Haskell-cafe] how to simplify ressources access and pipes steam

[☂Josh Chia (謝任中)]

Do you mean it's ugly because of the nested withHdf4PathP? If so, have you
considered ResourceT?

But I saw something else that seems more noteworthy. Why is withUhvPathP
being used to repeatedly open and close the same files using the filenames
contained in dif? (I suppose withHdf5PathP opens and closes HDF5 files.)
Why don't you open the files once in the beginning of your loop and close
them at the end? You can do this by wrapping everything in a ResourceT and
use allocate.

On Wed, May 20, 2020 at 6:25 PM Compl Yue <compl.yue at gmail.com> wrote:

> Maybe fork another thread, keep reading data and putting into a shared
> `MVar` / `TMVar`, then current thread keep taking from that var?
>
> > On 2020-05-20, at 14:23, PICCA Frederic-Emmanuel <
> frederic-emmanuel.picca at synchrotron-soleil.fr> wrote:
> >
> > Hello, I am writing a software which  do some data treatement from hdf5
> files.
> >
> > In order to access the data which are stored in arrays, I need to open
> and closes ressources.
> > This is the purpose of the withHdf5PathP function.
> >
> > given a file f and a UhvPath I end up with this
> >
> > withUhvPathP :: (MonadSafe m, Location l) => l -> UhvPath -> ((Int -> IO
> Geometry) -> m r) -> m r
> > withUhvPathP f (UhvPath m o d g w) gg =
> >      withHdf5PathP f m $ \m' ->
> >      withHdf5PathP f o $ \o' ->
> >      withHdf5PathP f d $ \d'->
> >      withHdf5PathP f g $ \g' ->
> >      withHdf5PathP f w $ \w' -> gg (\j -> do
> >                                      mu <- get_position m' j
> >                                      omega <- get_position o' j
> >                                      delta <- get_position d' j
> >                                      gamma' <- get_position g' j
> >                                      wavelength <- getValueWithUnit w' 0
> angstrom
> >                                      let positions =
> Data.Vector.Storable.fromList [mu, omega, delta, gamma']
> >                                      let source = Source wavelength
> >                                      pure $ Geometry Uhv source
> positions Nothing)
> >
> >
> > then I use this like this
> >
> > forever $ do
> >    (Chunk fp from to) <- await
> >    withFileP (openH5 fp) $ \f ->
> >      withHdf5PathP f imgs $ \dimgs ->
> >      withUhvPathP f dif $ \getDiffractometer ->
> >      withSamplePathP f samp $ \getSample ->
> >      forM_ [from..to-1] (\j -> yield =<< liftIO
> >                               (DataFrameHkl
> >                                <$> pure j
> >                                <*> get_image' det dimgs j
> >                                <*> getDiffractometer j
> >                                <*> getSample j))
> >
> > so once I open the resources, I use the getDiffratometer ((Int -> IO
> Geometry) -> m r) function give the position on the stream and it return
> the value at the j position.
> > the purpose of this is to open the ressources only once at the begining
> and then send the values in a Pipe via the yield function of pipes package.
> >
> > I hope, I was clear.
> >
> > 1) I find the withUhvPathP sort of ugly, and I would like to know if it
> could be written more elegantly, because I will need to write a lot's of
> these function for different types.
> >
> > 2) It is the right way to design a solution to my problem (open
> ressources and send each values into a stream).
> >
> > thanks for you attention.
> >
> > Frederic
> > _______________________________________________
> > Haskell-Cafe mailing list
> > To (un)subscribe, modify options or view archives go to:
> > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> > Only members subscribed via the mailman list are allowed to post.
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/haskell-cafe/attachments/20200521/d150ce13/attachment.html>