On 12/27/2011 3:29 PM, Bryan Jurish wrote:
From a more principled (as opposed to purely pragmatic) standpoint, I
think there are good reasons to allow size-0 dimensions across the
board, even in constructors like zeroes(), ones(), sequence(), xvals(),
etc. The main reason for this is to provide identity elements for
glue(). In my day job, I deal pretty much exclusively with
concatenative monoids (string languages), and these are pretty
uninteresting (not to mention intractable) without the empty string.
Putting it differently, I think glue() should be a (family of)
concatenative monoid(s) rather than just a boring old semigroup ;-)
The identity element argument seems like a plausible
justification/motivation for the existence and meaning of
such piddle shapes with 0-length dimensions.
Could the same effect be obtained by adding an explicit
dimension shape piddle/list to your CCS objects? It
seems like the missing piece with the current PDL is
a clever way to carry around the shape info in only
two piddles.
Cheers,
Chris
Thoughts, objections, comments, corrections, and further discussion welcome!
marmosets,
Bryan
On 2011-12-20 14:37:08, chm<[email protected]> appears to have
written:
On 12/20/2011 6:25 AM, Bryan Jurish wrote:
On 2011-12-18 22:56, chm wrote:
Fails tests:
MOOCOW/PDL-CCS-1.14.tar.gz (requires PDL::VectorValued)
Should be fixed (band-aided) in newest PDL::CCS on CPAN
(MOOCOW/PDL-CCS-1.15.tar.gz). The culprit seems to have been a change
in the PDL core's handling of Nx0 piddles somewhere between 2.4.9 and
2.4.9_015. Report filed as sourceforge bug #3462924
(https://sourceforge.net/tracker/?func=detail&aid=3462924&group_id=612&atid=100612).
This is a degenerate case, but it can easily happen in PDL::CCS (sparse
piddles) as a result of run-of-the-mill internal index-piddle twiddling.
Hi Bryan-
I'm not sure I comprehend what a [2,0] shaped
piddle means. My first thought is that it
should not be returned by dice_axis at all.
There have been some changes to PDL since 2.4.9
in *exactly* those edge cases. But the previous
handling caused segfaults in perl. I would like
for some feedback from the range-master based
on further discussion.
Maybe you could post separately to the mailing
list with some examples showing where non-trivial
0 length dimensions were supported, how they
arise in practice... In particular, is there
different code approaches that could work?
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