Hi here,
https://docs.oracle.com/cd/E19957-01/805-4940/z400091044d0/index.html
Just for information.
Now, an other thing to know.
Imagine I have a 2x2 matrix.
If I write in the computer memory 4 integer’s (1-2-3-4) in one time, in C this
will be in matrix representation :
1 2
3 4
But in Fortran, like in mathematics :
1 3
2 4
So operations on these two representations are completely differents.
Generaly computations on matrices are done on a very low level and use directly
the memory areas (no aware of indexing scheme).
Hope that helps
__
Greg
De : Luis Mochan
Envoyé le :jeudi 1 juin 2017 20:06
À : [email protected]
Objet :Re: [Pdl-general] SVD
Still confusing:
On Wed, May 31, 2017 at 03:36:33PM +1000, Karl Glazebrook wrote:
> column-major all the way down, as image processing came before matrix ops and
> i in A(i,j) is naturally the x-axis.
but the x axis displays horizontally, as row, and when matrices are
multiplied i is interpreted as column index, i.e., as index along row.
> i.e. A[0,1] is followed by A[1,0] in memory
You mean A[0,0] is followed by A[1,0] in memory, right?
So memory is arranged as in fortran arrays (first index fastest), but
the interpretation as row and column indices is different.
Regards,
Luis
>
>
> Karl
>
>
>
> > On 22 May 2017, at 6:32 am, Chris Marshall <[email protected]> wrote:
> >
> > Please ignore the following. Just mark me confused...
> >
> > --Chris
> >
> > On 5/21/2017 15:51, Chris Marshall wrote:
> >> The row-major and col-major for PDL has always
> >> confused me since, AFAICT the PDL dimensions and
> >> slicing syntax actually are column major in
> >> memory but we print them out in row-major.
> >>
> >> Maybe one of the original PDL developers could
> >> give an explanation (of the history at least!).
> >>
> >
> >
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