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Add utility to configure PDHG for with explicit TGV or TV regularisation - #1766

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Add utility to configure PDHG for with explicit TGV or TV regularisation#1766
paskino wants to merge 15 commits into
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paskino:add_TGV_utility

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@paskino

@paskino paskino commented Mar 28, 2024

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Description

Add utility to configure PDHG for with explicit TGV or TV regularisation with Least Squares.

Example Usage

An example is on CIL-Demos TGV_tomography.py

Changes

  • adds code to create the operators and function to configure PDHG with TGV explicit regularisation
  • adds max to BlockDataContainer
  • allows dot between a BlockDataContainer and a DataContainer

Testing you performed

Related issues/links

Checklist

  • I have performed a self-review of my code
  • I have added docstrings in line with the guidance in the developer guide
  • I have updated the relevant documentation
  • I have implemented unit tests that cover any new or modified functionality
  • CHANGELOG.md has been updated with any functionality change
  • Request review from all relevant developers
  • Change pull request label to 'Waiting for review'

Contribution Notes

Please read and adhere to the developer guide and local patterns and conventions.

  • The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in CIL (the Work) under the terms and conditions of the Apache-2.0 License
  • I confirm that the contribution does not violate any intellectual property rights of third parties

@samdporter

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Hey all,

This still needs a few changes. Currently the BlockOperator.direct method still returns a BlockDataContainer with shape (1,1) rather than a DataContainer. I'll do a few more tests to see if there's anything else that needs doing.

Would you like me to do a PR or let you guys take care of it?

@paskino paskino changed the title Add utility to configure PDHG for with explicit TGV regularisation Add utility to configure PDHG for with explicit TGV or TV regularisation Jul 25, 2024
@lauramurgatroyd lauramurgatroyd self-assigned this Aug 9, 2024

@lauramurgatroyd lauramurgatroyd left a comment

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I have added unit tests for setting up TV
I would appreciate a review of the code and the unit tests for that please before I write the TGV unit tests

Comment thread Wrappers/Python/cil/optimisation/utilities/PDHG.py
@MargaretDuff

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Hi @lauramurgatroyd - I like the style of the unit tests for explicit TV. They are comprehensive without being expensive. I have suggested a few changes to them and made some comments on the new utility file.

Comment thread Wrappers/Python/cil/optimisation/utilities/PDHG.py
from cil.optimisation.functions import MixedL21Norm, BlockFunction, L2NormSquared, ScaledFunction
from cil.optimisation.operators import BlockOperator, IdentityOperator, GradientOperator, \
SymmetrisedGradientOperator, ZeroOperator

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Can we call this file something other than PDHG.py? e.g. set_up_PDHG.py or something similar?

Forward operator.
data : AcquisitionData
alpha : float
Regularisation parameter.

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Regularisation parameter for which part?


def setup_explicit_TGV(A, data, alpha, delta=1.0, omega=1):
'''Function to setup LS + TGV problem for use with explicit PDHG

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Need a TGV equation in here, defining alpha and beta and omega

delta : float, default 1.0
The Regularisation parameter for the symmetrised gradient, beta, can be controlled by delta
with beta = delta * alpha.
omega : float, default 1.0

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Least squares uses c instead of omega, perhaps we could follow suit?

The constant in front of the data fitting term. Mathematicians like it to be 1/2 but it is 1 by default,
i.e. it is ignored if it is 1.

Returns:

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Could we add a code snippet to explain how to use the returned K and F in PDHG? Also need to explain briefly what we mean by "explicit"

function = F[0].function

np.testing.assert_equal(type(function), L2NormSquared)
np.testing.assert_array_equal(function.b.as_array(), ad.as_array())

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I would also be tempted to evaluate your functions on a small image, so reduce the size of the geometry to save computational cost, create a random test_data and then do
self.assertAlmostEqual(function(test_data), omega*LeastSquares(b=ad)(test_data))

np.testing.assert_equal(type(K[1].operator), GradientOperator)
ig = ad.geometry.get_ImageGeometry()
expected_grad = alpha*GradientOperator(ig)
np.testing.assert_allclose(expected_grad.direct(ad)[1].as_array(), expected_grad.direct(ad)[1].as_array())

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Is that comparing the same thing?

Comment on lines +115 to +116
np.testing.assert_allclose(expected_grad.direct(ad)[1].as_array(), K[1].direct(ad)[1].as_array(), 10**(-4))
np.testing.assert_allclose(expected_grad.direct(ad)[0].as_array(), K[1].direct(ad)[0].as_array(), 10**(-4))

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I think the expected_grad sould be operator on an image geometry not on acquisition data? Thus you should not be using ad


# F[1]

np.testing.assert_equal(MixedL21Norm, type(F[1]))

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Similarly, can you test this on an object?

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Create utility to configure TV and TGV regularisation with explicit PDHG

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