> > Glen Mabey wrote: > Hello, > > > > For some time, I have been working on a QtCore-based class that would be > a > > container class of arbitrary dimensionality. I did give a presentation > on > > this topic at DevDays-CA: >
Olivier Goffart responded: > Just my personal opinion on this: > > I do not think this class should be included in QtCore or even in a any > module > of Qt base. > > I think this is out of the scope of Qt. I do not see that many uses case > for > normal Qt applications. > > Perhaps it would be a better fit in a library that does numeric calculus. > I attended Glen's presentation at DevDays-CA. His introduction in this thread is a good overview of his QNDArray class, but I'll add my impression to focus the discussion: Glen's QNDArray (template) class: (a)- approximates the "Numpy" module available in Python for multi-dimensional data sets (b)- is highly performant (e.g., native C++ with attention to native platform types) (c)- is designed for VERY large data sets to be stored/accessed in a "native" format (e.g., data access is logically starting at "offsets" with "skip-levels" between internal "values") Olivier raises a fair point, regarding the nature of "QtCore" (what should be included in there?), but IMHO the QNDArray makes great sense in the Qt cross-platform-offering (some module). Specifically: (1) It is an "enabling" technology that encourages Qt/C++ use where other languages/technologies would have been used. Glen's class is the FIRST third-party implementation I've seen (ever) that we could actually use (we work with data sets in the GB and TB level, and time-sensitive performance is critical). If added to Qt, we would consider dropping our in-house implementations to use Glen's QNDArray (this is serious investigation at present). (2) Qt/QML is now heavily focused on OpenGL. We're looking at Glen's QNDArray to be the "native" data sets that would be manipulated inside the "Modern-OpenGL-static-pipeline" (great talks by Sean Harmer at DevDays-CA on what's involved there). IMHO, (2) is the stronger argument: Qt needs to provide strong support for users to write their geometry-shaders and vertex-shaders. This is mere raw data-set manipulation. It seems like Qt should provide some out-of-the-box data-set "accessor/manipulator" for those of us with very large data sets (and of course, it should be fast). So, I'm not picky about "which" module it ends up within, but I like the idea of the QNDArray in some "Qt-proper" module. The "ideal" scenario would be if Qt's "OpenGL" or "charts" or other higher-level Qt-proper modules interfaced directly with this "large-data-set-object". Because it is a mere "representation-format" with no external coupling, I'd be fine with it added to QtCore, but I'd accept other suggestions. I agree with Olivier that the "numeric calculus" domain is somewhat "un-bounded". However, it seems like Qt needs to provide a data-set *representation* format, especially since our job in Qt5+ is to implement OpenGL shaders (which are mere raw-data-set-manipulators). --charley
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