On Fri, Jul 5, 2013 at 1:15 AM, Dmitriy Lyubimov <dlie...@gmail.com> wrote:
> For anyone good at scala DSLs, the following is the puzzle i can't seem to
> figure at the moment.
>
> I mentioned before that I implemented assignment notations to a row or a
> block, e.g. for a row vector : A(5,::) := (1,2,3)
>
> what it really translates into in this particular case is
>
> A.viewRow(5).assign(new Vector(new double[]{1,2,3}))
>
>
> One thing i can't quite figure for in-core matrix DSL is how to translate
> element assignments such as
>
> A(5,5) := 2.0
>
> into A.setQuick(5,5,2.0)
>
> while still having
>
> val k = A(5,5)
>
> translating into
> val k = A.getQuick(5,5).
>
>
> it could be implemented with a "elementView" analogue but would require the
> element view object creation -- which is, first, a big no-no (too
> expensive) for a simple solitary element assignment (or read-out)
> operation, and secondly, reading the element such as A(5,5) * 2.0 would
> also involve view element object creation with implicit conversion to
> Double whereas it is not even needed at all in this case.
>
> at this point i have only a very obvious apply(Double,Double):Double =
> m.getQuick(...), i.e. only element reads are supported with that syntax.
>
> I am guessing Jake, if anyone, might have an idea here... thanks.
>
Hmmm... right off the top of my head, no. But my play-DSL is pretty
free of operators, as that level of scala cleverness worries me a little,
when it comes to making sure we're sticking to efficient operations
under the hood.
>
>
>
> On Thu, Jul 4, 2013 at 11:23 PM, Dmitriy Lyubimov <dlie...@gmail.com>
> wrote:
>
> > FWIW, Givens streaming qr will be a bit more economical on memory than
> > Householder's since it doesn't need the full buffer to compute R and
> > doesn't need to keep entire original matrix around.
> >
> >
> > On Thu, Jul 4, 2013 at 11:15 PM, Dmitriy Lyubimov <dlie...@gmail.com
> >wrote:
> >
> >> Ted,
> >>
> >> would it make sense to port parts of QR in-core row-wise Givens solver
> >> out of SSVD to work on any Matrix? I know givens method is advertised as
> >> stable but not sure if it is the fastest accepted one. I guess they are
> all
> >> about the same.
> >>
> >> If yes, i will need also to port the UpperTriangular matrix to adhere to
> >> all the bells and wistles, and also have some sort of RowShift matrix (a
> >> much simpler analogue of Pivoted matrix for row-rolled buffers). would
> that
> >> make sense?
> >>
> >> thanks.
> >> -D
> >>
> >>
> >
>
--
-jake
