Experimental Physics and Industrial Control System
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Subject: |
Re: PVD/PVA: Examples for multi-dimensional arrays? |
From: |
Marty Kraimer via Core-talk <[email protected]> |
To: |
[email protected] |
Date: |
Wed, 21 Nov 2018 15:32:54 -0500 |
On 11/21/18 11:10 AM, Ralph Lange via
Core-talk wrote:
Hi Mark,
What do
you mean by "support"? NTNDArrays are certainly
N-dimensional. Do you want the API to allow extracting
rows/columns, etc.?
Hm.
The problem with leaving n-dim support to the
application is that every application using n-dim arrays
will have to do its own implementation of the accessors.
Also, because of that, these n-dim arrays will likely not
be compatible between applications.
Does that sound like I am asking for a new normative
type?
Cheers,
~Ralph
At the very beginning of PVData development, i. e. the JavaIOC, a
deliberate decision was made that pvData would only support 1 dim
arrays.
The problem with supporting more dimensions is how many and how to
define each dimension.
Just consider a 2d array. It it a 2d matrix? Is it a sparse matrix?
Is it a table?
I also remember a request for pvData defining a map type.
Where do we stop?
At the very beginning it was decided that the following types
would be supported
1) scalars of numeric , boolean, and string.
2) 1d arrays of each scalar type
3) structures
4) 1d structure arrays
This was defined in 2006.
The only types that were added later are:
5) union
6) 1d union array.
It is ONLY data of above types that need to be supported by the
pva network protocol.
Also from the beginning it was assumed that more complex types would
be supported via structure definitions.
This later became the normative types.
Note that normative types already has definiintions for NTTable,
NTMatrix, and NTHistogram.
Each of these is a different type of 2d array.
NTNDArray includes a multi dimensional array plus lots more.
No normative type required any changes to the network protocol.
Recently there was a discussion of pvAccess directly supporting
compression.
Although it was talking about pvAccess it would probably have to
involve pvData.
For the same reason for not supporting multi deminsional array
compression should NOT be directly supported by pvData/pvAccess.
What kind of compression?
lossless?, JPEG?, etc, etc.
Would each additional type require changes to the pva network
protocol.
Note that areaDetecter already supports a few compression types.
Marty
|
- Replies:
- Re: PVD/PVA: Examples for multi-dimensional arrays? Mark Rivers via Core-talk
- References:
- PVD/PVA: Examples for multi-dimensional arrays? Ralph Lange via Core-talk
- Re: PVD/PVA: Examples for multi-dimensional arrays? Michael Davidsaver via Core-talk
- Re: PVD/PVA: Examples for multi-dimensional arrays? Ralph Lange via Core-talk
- Re: PVD/PVA: Examples for multi-dimensional arrays? Mark Rivers via Core-talk
- Re: PVD/PVA: Examples for multi-dimensional arrays? Ralph Lange via Core-talk
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ANJ, 21 Nov 2018 |
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