Hi Ingo,

My best answer to your direct question is a non-answer: only you know what is 
your easiest workflow. However, if bart does everything via new files for each 
stage, and you feel (as sounds likely from your description) that the various 
transformations can be done quicker but still correctly using PDL slicing stuff 
(especially as, with vaffine transformations like slice and mv, a copy is not 
made of the data), then you should run with that. Probably you’d want to have 
PDL write out to a file for stuff that bart is best at. I would note that one 
of your example bart commands is “nufft”, and PDL has several FFT 
implementations available that might be useful to compare that to (Slatec, 
FFTW3, the provided PDL::FFT).

PDL::IO::FlexRaw is probably fine for memory-mapping stuff, though I’ve not 
really used it. I have dabbled with PDL::IO::FastRaw to help with Photonic, and 
that works fine for stuff that’s too big for RAM. If you find any problems with 
FlexRaw, please report them here so they can be fixed. Once you have stuff 
working, I hope you’ll put it on CPAN!

Best regards,
Ed

________________________________
From: Ingo Schmid via pdl-general <[email protected]>
Sent: Wednesday, May 15, 2024 2:04:41 PM
To: perldl <[email protected]>
Subject: [Pdl-general] PDL and bart


Hi,

I both use PDL and recently started using bart 
(https://mrirecon.github.io/bart/). Documentation is somewhere between 
non-existent and horribly insufficient, before you ask.

It has implementations of MRI reconstruction algorithms and its file format is 
complex float, very very similar to the FlexRaw format. They come in pairs of 
binary data cfl and text hdr files.

Here's a sample dump, of which only the #Dimensions lines are essential:

# Dimensions
200 200 200 1 1 1 1 1 1 1 1 1 1 1 1 1
# Command
pics -d 5 -R W:7:0:0.0015 -e -i 100 -S -t traj549 reshData549 sens reco_l1
# Files
 >reco_l1 <sens <reshData549 <traj549
# Creator
BART v0.8.00-196-g5947a32

I intend to wrap readflex/writeflex calls into readcfl/writecfl (there are 
matlab and python interfaces).

Every command reads one or more files and the result is stored in a new one. 
This, of course, is not always efficient if things are temporary and fit into 
memory. The good thing is, you can run these from any shell/command prompt.

For example
> bart transpose 1 11 _tmp _tmp1

reads _tmp, swaps dimensions 1 and 11 (starts at 0) and writes _tmp1

or
> bart slice 1 $c1 $eof _eof_c1;
creates a slice at position $c1 in dimension 1 and writes that to _eof_c1.

These are things done much more efficiently in PDL, for example. Others are 
very useful (nufft, nlinv), though specific to the field (pics, cc).

Now, here comes my question. Do you see a straight-forward workflow to use both 
bart and PDL in its optimal way?

How to best memory map files, possibly directly into a piddle?

I am grateful for your input.

Best wishes

Ingo
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