Explicit tgv backend

[samtygier-stfc]

I made a branch of #1986 within the MI repo so that the PR can access the secrets on actions (I can't see a simple way to give the fork access).

Issue

closes #1985

Description

Implementation of a Total Generalised Variation regulariser for Least Squares problems. It works both with PDHG and the SPDHG algorithms.

Controls to from the interface that are required:

1. alpha, regularisation parameter as in Eq. 3.5 https://royalsocietypublishing.org/doi/10.1098/rsta.2020.0193
2. gamma, ratio beta/alpha, wrt to Eq. 3.5 https://royalsocietypublishing.org/doi/10.1098/rsta.2020.0193
3. regulariser, whether TV or TGV

Testing

Edit ReconstructWindowView.regulariser to return "TGV". In the reconstruction window select CIL:PDHG-TV, and check that it still does a reconstruction.

Documentation

Wait for the GUI side

[coveralls]

coverage: 73.005% (-0.4%) from 73.358%
when pulling 0d07c18 on 1986-explicit_TGV
into b370ba9 on main.

[MikeSullivan7]

Selecting CIL:PDHG-TV after changing the regulariser to TGV doesnt seem to produce a reconstruction preview, i.e.

and the reconstruction just gives a blank reconstruction.

I will do a deeper investigation to figure out what exactly is going on

[samtygier-stfc]

Do you get anything if you increase the number of iterations?

[MikeSullivan7]

Ah yes, I didnt put the number of iterations high enough, my bad!

[MikeSullivan7]

After using CIL: PDHG-TV with "TGV" selected and toggling the "stochastic" option, I get an error:

2024-04-25 09:42:30,166 [mantidimaging.gui.dialogs.async_task.task:L53] ERROR: Failed to execute task: tuple index out of range
Traceback (most recent call last):
  File "C:\Users\ddb29996\mantidimaging\mantidimaging\gui\dialogs\async_task\task.py", line 50, in run
    self.result = call_with_known_parameters(self.task_function, **self.kwargs)
  File "C:\Users\ddb29996\mantidimaging\mantidimaging\core\utility\func_call.py", line 12, in call_with_known_parameters
    return func(**ka)
  File "C:\Users\ddb29996\mantidimaging\mantidimaging\gui\windows\recon\model.py", line 132, in run_preview_recon
    recon.data[0] = reconstructor.single_sino(images.sino(slice_idx),
  File "C:\Users\ddb29996\mantidimaging\mantidimaging\core\reconstruct\cil_recon.py", line 249, in single_sino
    algo = SPDHG(f=F,
  File "C:\Users\ddb29996\AppData\Local\miniforge3\envs\mantidimaging-dev\lib\site-packages\cil\optimisation\algorithms\SPDHG.py", line 105, in __init__
    self.set_up(f=f, g=g, operator=operator, tau=tau, sigma=sigma,
  File "C:\Users\ddb29996\AppData\Local\miniforge3\envs\mantidimaging-dev\lib\site-packages\cil\optimisation\algorithms\SPDHG.py", line 156, in set_up
    norms = [operator.get_item(i,0).norm() for i in range(self.ndual_subsets)]
  File "C:\Users\ddb29996\AppData\Local\miniforge3\envs\mantidimaging-dev\lib\site-packages\cil\optimisation\algorithms\SPDHG.py", line 156, in <listcomp>
    norms = [operator.get_item(i,0).norm() for i in range(self.ndual_subsets)]
  File "C:\Users\ddb29996\AppData\Local\miniforge3\envs\mantidimaging-dev\lib\site-packages\cil\optimisation\operators\BlockOperator.py", line 136, in get_item
    return self.operators[index]
IndexError: tuple index out of range
2024-04-25 09:42:30,168 [mantidimaging.gui.mvp_base.view:L46] ERROR: show_error_dialog(): Encountered error while trying to reconstruct: tuple index out of range

Is this expected?

[samtygier-stfc]

Its expected not to work :-). The GUI (when it is done), will block setting stochastic for TGV. But we should probably have a better error message here.

[MikeSullivan7]

Looks good, seems to match up with the paper and give good results with a higher number of iterations