Hi Isaac,
it's just thought that it could be done like this:
Copy operation: start = 0, stride = 1
target_index = 0 + source_index * 1
Reflection: start = max_index, stride = -1
target_index = max_index + source_index * -1
So a negative stride in one dimensions would go "backwards", thus do a
reflection in this direction. In practice the stride parameter is
probably an unsigned integer and thus running out of bounds instead of
going backwards, as you say.
Werner
On 25.04.2017 23:48, Isaac Gerg wrote:
Hi Werner, thanks for the reply. Let's wrestle with this a bit. So
numpy does their indexing by strides, the stride for each dimension.
hdf5 does their "striding" across the data in the sense of more of a
selection than a stride. I would be inclined to say that even a
negative stride wouldnt allow this. The problem is the stride is a
simply stride and not one based on dimension index so the stride can't
wrap so you end up with out of bounds issues with the datasets. Does
this seem right?
On Tue, Apr 25, 2017 at 5:29 PM, Werner Benger <[email protected]
<mailto:[email protected]>> wrote:
Hi Isaac,
without proof, but I could imagine it's possible to implement a
shear operation via hyperslabs. If so, then hyperslabs could be
used to implement rotations:
e.g.
https://www.ocf.berkeley.edu/~fricke/projects/israel/paeth/rotation_by_shearing.html
<https://www.ocf.berkeley.edu/%7Efricke/projects/israel/paeth/rotation_by_shearing.html>
To do a transpose, one would need a reflection in addition to
rotation (e.g. http://techieme.in/matrix-rotation/
<http://techieme.in/matrix-rotation/> ) , and I guess doing this
operation of a reflection is not possible via hyperslabs, so doing
a transpose is out of reach. Probably it would require to allow
something like a negative stride value...
Werner
On 25.04.2017 22:24, Isaac Gerg wrote:
Hi Quincy, I just was reading about point selections and was
wondering if that's the way we would go. Thanks for confirming!
On Tue, Apr 25, 2017 at 4:21 PM, Quincey Koziol <[email protected]
<mailto:[email protected]>> wrote:
> On Apr 25, 2017, at 1:02 PM, Isaac Gerg
<[email protected] <mailto:[email protected]>> wrote:
>
> A coworker and I are mulling over if its possible to take a
simple 3x3 matrix (stored row major) in a dataspace and write
it out transposed to disk using a hyperslab. It seems that
the grammer provided by start, stride, blocks, and count
won't allow for this. We hope we are wrong! It is possible
to do this?
Hyperslabs won’t do this, but you could use a point
selection instead.
Quincey
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___________________________________________________________________________
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Center for Computation & Technology at Louisiana State University (CCT/LSU)
2019 Digital Media Center, Baton Rouge, Louisiana 70803
Tel.: +1 225 578 4809 Fax.: +1 225 578-5362
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