comment on

your approach really physicalizes arrays from 2D to 4D

No, it does not. It uses clump and slice, both of which are affine transformations (as shown by the P2Child=>1 in https://github.com/PDLPorters/pdl/blob/master/Basic/Slices/slices.pd for the relevant operations). Physicalising only happens on output or use in calculations, and when loop fusion comes in, not even then. I'd love to hear of an approach that Kronecker-products m1,n1 and m2,n2 matrices without producing a m1*m2,n1*n2 in-memory object. While you're pondering that, please show some numbers demonstrating these "grave consequences" :-)

Is this a bug in PDL::NiceSlice, documentation flaw, or just me reading it incorrectly?

You're going to need to show some code that you're saying is behaving unexpectedly. This worked as described (with output):

pdl> p sequence(2)->(*1)
[
 [0]
 [1]
]
pdl> p sequence(2)->(*)
[
 [0]
 [1]
]
pdl> p sequence(2)->(*,*)
[
 [
  [0]
 ]
 [
  [1]
 ]
]
[download]

Naturally, you need to make sure a use PDL::NiceSlice is in scope. You will have noticed that generally I avoid using it in core PDL code, because it both slows down module-loading, and has limitations; see PDL::LinearAlgebra, where I had to remove a lot of it in favour of building arguments to slice that took account of adding optional parts for PDL::Complex.

In reply to Re^4: Kronecker Product by etj
in thread Kronecker Product by choroba

Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
Want more info? How to link or How to display code and escape characters are good places to start.


Syntactic Confectionery Delight
	PerlMonks