Tool to represent graphically the memory layout of vlsv files

[ykempf]

It would be nice to have a tool plotting the memory layout of vlsv files. Since everything is already in an xml tree, I suppose that marching through it with some python xml functions would be easy, retrieving the start bytes of all fields and plotting them in order.

The use case we would have now, in Vlasiator, would be to check easily how much space is used for real-space fields vs. velocity space saved every n cells, and estimate how the file size would grow when going to n/2 spacing. We can do it by hand looking at data size * vector size * entries, but a quick graphical tool would be cool.

Issue submitted for the record, no hurry at all.

[ykempf]

I made a test script, I'll submit it later.

[sandroos]

This would have to operate on general (non-Vlasiator-specific) level to be added to vlsv. A simple tool for listing the contents of the vlsv file has been on the back of my head for a long time, but i've never needed it so it's not done.

I suppose, if you'd just get an ascii output like

<variable name> <size in bytes> <other data fields>

it would be a simple task to plot that with a Python script in a generic way?

[ykempf]

@sandroos this is purely vlsv (and python obviously), no Vlasiator specifics.

By the way (also @galfthan @ursg) we could move vlsvls.sh and vlsvxml.sh from the Vlasiator repo to here, I don't see them having any Vlasiator specifics.

[ykempf]

This was merged.