#!/usr/bin/env python3
"""
Solvers for the tomographic reconstruction problem.
@author: Nicola VIGANÒ, Computational Imaging group, CWI, The Netherlands,
and ESRF - The European Synchrotron, Grenoble, France
"""
import copy as cp
from abc import ABC, abstractmethod
from typing import Any, Callable, Optional, Union
from collections.abc import Sequence
import numpy as np
from numpy.typing import DTypeLike, NDArray
from tqdm.auto import tqdm
from . import data_terms, filters, operators, projectors, regularizers
eps = np.finfo(np.float32).eps
NDArrayFloat = NDArray[np.floating]
[docs]
class SolutionInfo:
"""Reconstruction info."""
method: str
iterations: int
max_iterations: int
residual0: Union[float, np.floating]
residual0_cv: Union[float, np.floating]
residuals: NDArrayFloat
residuals_cv: NDArrayFloat
tolerance: Union[float, np.floating, None]
def __init__(
self,
method: str,
max_iterations: int,
tolerance: Union[float, np.floating, None],
residual0: float = np.inf,
residual0_cv: float = np.inf,
) -> None:
self.method = method
self.max_iterations = max_iterations
self.tolerance = tolerance
self.residual0 = residual0
self.residual0_cv = residual0_cv
self.residuals = np.zeros(max_iterations)
self.residuals_cv = np.zeros(max_iterations)
self.iterations = 0
@property
def residuals_rel(self) -> NDArrayFloat:
return self.residuals / self.residual0
@property
def residuals_cv_rel(self) -> NDArrayFloat:
return self.residuals_cv / self.residual0_cv
[docs]
class Solver(ABC):
"""
Initialize the base solver class.
Parameters
----------
verbose : bool, optional
Turn on verbose output. The default is False.
tolerance : Optional[float], optional
Tolerance on the data residual for computing when to stop iterations.
The default is None.
relaxation : float, optional
The relaxation length. The default is 1.0.
data_term : Union[str, data_terms.DataFidelityBase], optional
Data fidelity term for computing the data residual. The default is "l2".
data_term_test : Optional[data_terms.DataFidelityBase], optional
The data fidelity to be used for the test set.
If None, it will use the same as for the rest of the data.
The default is None.
"""
def __init__(
self,
verbose: bool = False,
leave_progress: bool = True,
relaxation: float = 1.0,
tolerance: Optional[float] = None,
data_term: Union[str, data_terms.DataFidelityBase] = "l2",
data_term_test: Union[str, data_terms.DataFidelityBase, None] = None,
):
self.verbose = verbose
self.leave_progress = leave_progress
self.relaxation = relaxation
self.tolerance = tolerance
self.data_term = self._initialize_data_fidelity_function(data_term)
if data_term_test is None:
data_term_test = self.data_term
else:
data_term_test = self._initialize_data_fidelity_function(data_term_test)
self.data_term_test = cp.deepcopy(data_term_test)
[docs]
def info(self) -> str:
"""
Return the solver info.
Returns
-------
str
Solver info string.
"""
return type(self).__name__
[docs]
def upper(self) -> str:
"""
Return the upper case name of the solver.
Returns
-------
str
Upper case string name of the solver.
"""
return type(self).__name__.upper()
[docs]
def lower(self) -> str:
"""
Return the lower case name of the solver.
Returns
-------
str
Lower case string name of the solver.
"""
return type(self).__name__.lower()
@abstractmethod
def __call__(
self, A: operators.BaseTransform, b: NDArrayFloat, *args: Any, **kwds: Any
) -> tuple[NDArrayFloat, SolutionInfo]:
"""Execute the reconstruction of the data.
Parameters
----------
A : operators.BaseTransform
The projection operator.
b : NDArrayFloat
The data to be reconstructed.
Returns
-------
Tuple[NDArrayFloat, SolutionInfo]
The reconstruction and related information.
"""
@staticmethod
def _initialize_data_fidelity_function(data_term: Union[str, data_terms.DataFidelityBase]) -> data_terms.DataFidelityBase:
if isinstance(data_term, str):
if data_term.lower() == "l2":
return data_terms.DataFidelity_l2()
elif data_term.lower() == "kl":
return data_terms.DataFidelity_KL()
else:
raise ValueError(f"Unknown data term: '{data_term}', only accepted terms are: 'l2' | 'kl'.")
elif isinstance(data_term, (data_terms.DataFidelity_l2, data_terms.DataFidelity_KL)):
return cp.deepcopy(data_term)
else:
raise ValueError(f"Unsupported data term: '{data_term.info()}', only accepted terms are 'kl' and 'l2'-based.")
@staticmethod
def _initialize_regularizer(
regularizer: Union[regularizers.BaseRegularizer, None, Sequence[regularizers.BaseRegularizer]]
) -> Sequence[regularizers.BaseRegularizer]:
if regularizer is None:
return []
elif isinstance(regularizer, regularizers.BaseRegularizer):
return [regularizer]
elif isinstance(regularizer, (list, tuple)):
check_regs_ok = [isinstance(r, regularizers.BaseRegularizer) for r in regularizer]
if not np.all(check_regs_ok):
raise ValueError(
"The following regularizers are not derived from the regularizers.BaseRegularizer class: "
f"{np.array(np.arange(len(check_regs_ok))[np.array(check_regs_ok, dtype=bool)])}"
)
else:
return list(regularizer)
else:
raise ValueError("Unknown regularizer type.")
@staticmethod
def _initialize_b_masks(
b: NDArrayFloat, b_mask: Optional[NDArrayFloat], b_test_mask: Optional[NDArrayFloat]
) -> tuple[Optional[NDArrayFloat], Optional[NDArrayFloat]]:
if b_test_mask is not None:
if b_mask is None:
b_mask = np.ones_like(b)
# As we are being passed a test residual pixel mask, we need
# to make sure to mask those pixels out from the reconstruction.
# At the same time, we need to remove any masked pixel from the test count.
b_mask, b_test_mask = b_mask * (1 - b_test_mask), b_test_mask * b_mask
return (b_mask, b_test_mask)
[docs]
class FBP(Solver):
"""Implementation of the Filtered Back-Projection (FBP) algorithm."""
def __init__(
self,
verbose: bool = False,
leave_progress: bool = False,
regularizer: Union[Sequence[regularizers.BaseRegularizer], regularizers.BaseRegularizer, None] = None,
data_term: Union[str, data_terms.DataFidelityBase] = "l2",
fbp_filter: Union[str, NDArrayFloat, filters.Filter] = "ramp",
pad_mode: str = "constant",
):
"""Initialize the Filtered Back-Projection (FBP) algorithm.
Parameters
----------
verbose : bool, optional
Turn on verbose output. The default is False.
leave_progress: bool, optional
Leave the progress bar after the computation is finished. The default is True.
regularizer : Sequence[regularizers.BaseRegularizer] | regularizers.BaseRegularizer | None, optional
NOT USED, only exposed for compatibility reasons.
data_term : Union[str, data_terms.DataFidelityBase], optional
NOT USED, only exposed for compatibility reasons.
fbp_filter : Union[str, NDArrayFloat], optional
FBP filter to use. Either a string from scikit-image's list of `iradon` filters, or an array. The default is "ramp".
pad_mode: str, optional
The padding mode to use for the linear convolution. The default is "constant".
"""
super().__init__(verbose=verbose)
if isinstance(fbp_filter, str):
fbp_filter = fbp_filter.lower()
self.fbp_filter = fbp_filter
self.pad_mode = pad_mode
[docs]
def info(self) -> str:
"""
Return the solver info.
Returns
-------
str
Solver info string.
"""
if isinstance(self.fbp_filter, str):
return super().info() + "(F:" + self.fbp_filter.upper() + ")"
elif isinstance(self.fbp_filter, np.ndarray):
return super().info() + "(F:" + filters.FilterCustom.__name__.upper() + ")"
else:
return super().info() + "(F:" + type(self.fbp_filter).__name__.upper() + ")"
def __call__( # noqa: C901
self,
A: operators.BaseTransform,
b: NDArrayFloat,
iterations: int = 0,
x0: Optional[NDArrayFloat] = None,
lower_limit: Union[float, NDArrayFloat, None] = None,
upper_limit: Union[float, NDArrayFloat, None] = None,
x_mask: Optional[NDArrayFloat] = None,
b_mask: Optional[NDArrayFloat] = None,
) -> tuple[NDArrayFloat, SolutionInfo]:
"""
Reconstruct the data, using the FBP algorithm.
Parameters
----------
A : BaseTransform
Projection operator.
b : NDArrayFloat
Data to reconstruct.
iterations : int
Number of iterations.
x0 : Optional[NDArrayFloat], optional
Initial solution. The default is None.
lower_limit : Union[float, NDArrayFloat], optional
Lower clipping value. The default is None.
upper_limit : Union[float, NDArrayFloat], optional
Upper clipping value. The default is None.
x_mask : Optional[NDArrayFloat], optional
Solution mask. The default is None.
b_mask : Optional[NDArrayFloat], optional
Data mask. The default is None.
Raises
------
ValueError
In case the data is 1D.
Returns
-------
Tuple[NDArrayFloat, SolutionInfo]
The reconstruction, and None.
"""
if len(b.shape) < 2:
raise ValueError(f"Data should be at least 2-dimensional (b.shape = {b.shape})")
info = SolutionInfo(self.info(), max_iterations=0, tolerance=0.0)
if isinstance(self.fbp_filter, str):
if self.fbp_filter in ("mr", "data"):
local_filter = filters.FilterMR(projector=A)
else:
local_filter = filters.FilterFBP(filter_name=self.fbp_filter)
elif isinstance(self.fbp_filter, np.ndarray):
local_filter = filters.FilterCustom(self.fbp_filter)
else:
local_filter = self.fbp_filter
local_filter.pad_mode = self.pad_mode
if isinstance(A, operators.ProjectorOperator):
pre_weights = A.get_pre_weights()
if pre_weights is not None:
b = b * pre_weights
b_f = local_filter(b)
x = A.T(b_f)
if lower_limit is not None or upper_limit is not None:
x = x.clip(lower_limit, upper_limit)
if x_mask is not None:
x *= x_mask
return x, info
[docs]
class SART(Solver):
"""Solver class implementing the Simultaneous Algebraic Reconstruction Technique (SART) algorithm."""
[docs]
def compute_residual(
self,
A: Callable,
b: NDArrayFloat,
x: NDArrayFloat,
A_num_rows: int,
b_mask: Optional[NDArrayFloat],
) -> NDArrayFloat:
"""Compute the solution residual.
Parameters
----------
A : Callable
The forward projector.
b : NDArrayFloat
The detector data.
x : NDArrayFloat
The current solution
A_num_rows : int
The number of projections.
b_mask : Optional[NDArrayFloat]
The mask to apply
Returns
-------
NDArrayFloat
The residual.
"""
fp = np.stack([A(x, ii) for ii in range(A_num_rows)], axis=-1)
fp = np.ascontiguousarray(fp, dtype=b.dtype)
res = fp - b
if b_mask is not None:
res *= b_mask
return res
def __call__( # noqa: C901
self,
A: Union[Callable[[NDArray, int], NDArray], projectors.ProjectorUncorrected],
b: NDArrayFloat,
iterations: int,
A_num_rows: Optional[int] = None,
At: Optional[Callable] = None,
x0: Optional[NDArrayFloat] = None,
lower_limit: Union[float, NDArrayFloat, None] = None,
upper_limit: Union[float, NDArrayFloat, None] = None,
x_mask: Optional[NDArrayFloat] = None,
b_mask: Optional[NDArrayFloat] = None,
) -> tuple[NDArrayFloat, SolutionInfo]:
"""
Reconstruct the data, using the SART algorithm.
Parameters
----------
A : Union[Callable, BaseTransform]
Projection operator.
b : NDArrayFloat
Data to reconstruct.
iterations : int
Number of iterations.
A_num_rows : int
Number of projections.
x0 : Optional[NDArrayFloat], optional
Initial solution. The default is None.
At : Callable, optional
The back-projection operator. This is only needed if the projection operator does not have an adjoint.
The default is None.
lower_limit : Union[float, NDArrayFloat], optional
Lower clipping value. The default is None.
upper_limit : Union[float, NDArrayFloat], optional
Upper clipping value. The default is None.
x_mask : Optional[NDArrayFloat], optional
Solution mask. The default is None.
b_mask : Optional[NDArrayFloat], optional
Data mask. The default is None.
Returns
-------
Tuple[NDArrayFloat, SolutionInfo]
The reconstruction, and the residuals.
"""
if isinstance(A, projectors.ProjectorUncorrected):
p = A
if not p.projector_backend.has_individual_projs:
raise ValueError("The projector needs to have enabled single projections.")
A = lambda x, ii: p.fp_angle(x, ii) # noqa: E731
if isinstance(p, projectors.ProjectorAttenuationXRF):
At = lambda y, ii: p.bp_angle(y, ii, single_line=True) # noqa: E731
else:
At = lambda y, ii: p.bp_angle(y, ii) # noqa: E731
A_num_rows = len(p.angles_rot_rad)
elif At is None:
raise ValueError("Parameter `At` is required, if `A` is not a projector.")
elif A_num_rows is None:
raise ValueError("Parameter `A_num_rows` is required, if `A` is not a projector.")
# Back-projection diagonal re-scaling
b_ones = np.ones_like(b)
if b_mask is not None:
b_ones *= b_mask
tau = [At(b_ones[..., ii, :], ii) for ii in range(A_num_rows)]
tau = np.abs(np.stack(tau, axis=-2))
tau[(tau / np.max(tau)) < 1e-5] = 1
tau = self.relaxation / tau
# Forward-projection diagonal re-scaling
x_ones = np.ones([*tau.shape[:-2], tau.shape[-1]], dtype=tau.dtype)
if x_mask is not None:
x_ones *= x_mask
sigma = [A(x_ones, ii) for ii in range(A_num_rows)]
sigma = np.abs(np.stack(sigma, axis=-2))
sigma[(sigma / np.max(sigma)) < 1e-5] = 1
sigma = 1 / sigma
if x0 is None:
x0 = np.zeros_like(x_ones)
else:
x0 = np.array(x0).copy()
x = x0
info = SolutionInfo(self.info(), max_iterations=iterations, tolerance=self.tolerance)
if self.tolerance is not None:
res = self.compute_residual(A, b, x, A_num_rows=A_num_rows, b_mask=b_mask)
info.residual0 = np.linalg.norm(res.flatten())
rows_sequence = np.random.permutation(A_num_rows)
algo_info = f"- Performing {self.upper()} iterations: "
for ii in tqdm(range(iterations), desc=algo_info, disable=(not self.verbose), leave=self.leave_progress):
info.iterations += 1
for ii_a in rows_sequence:
res = A(x, ii_a) - b[..., ii_a, :]
if b_mask is not None:
res *= b_mask[..., ii_a, :]
x -= At(res * sigma[..., ii_a, :], ii_a) * tau[..., ii_a, :]
if lower_limit is not None:
x = np.fmax(x, lower_limit)
if upper_limit is not None:
x = np.fmin(x, upper_limit)
if x_mask is not None:
x *= x_mask
if self.tolerance is not None:
res = self.compute_residual(A, b, x, A_num_rows=A_num_rows, b_mask=b_mask)
info.residuals[ii] = np.linalg.norm(res)
if self.tolerance > info.residuals[ii]:
break
return x, info
[docs]
class MLEM(Solver):
"""
Initialize the MLEM solver class.
This class implements the Maximul Likelihood Expectation Maximization (MLEM) algorithm.
Parameters
----------
verbose : bool, optional
Turn on verbose output. The default is False.
leave_progress: bool, optional
Leave the progress bar after the computation is finished. The default is True.
tolerance : Optional[float], optional
Tolerance on the data residual for computing when to stop iterations.
The default is None.
regularizer : Sequence[regularizers.BaseRegularizer] | regularizers.BaseRegularizer | None, optional
Regularizer to be used. The default is None.
data_term : Union[str, data_terms.DataFidelityBase], optional
Data fidelity term for computing the data residual. The default is "l2".
data_term_test : Optional[data_terms.DataFidelityBase], optional
The data fidelity to be used for the test set.
If None, it will use the same as for the rest of the data.
The default is None.
"""
def __init__(
self,
verbose: bool = False,
leave_progress: bool = True,
tolerance: Optional[float] = None,
regularizer: Union[Sequence[regularizers.BaseRegularizer], regularizers.BaseRegularizer, None] = None,
data_term: Union[str, data_terms.DataFidelityBase] = "kl",
data_term_test: Union[str, data_terms.DataFidelityBase, None] = None,
):
super().__init__(
verbose=verbose,
leave_progress=leave_progress,
tolerance=tolerance,
data_term=data_term,
data_term_test=data_term_test,
)
self.regularizer = self._initialize_regularizer(regularizer)
[docs]
def info(self) -> str:
"""
Return the MLEM info.
Returns
-------
str
info string.
"""
return Solver.info(self) + f"(B:{self.data_term.background:g})" if self.data_term.background is not None else ""
def __call__( # noqa: C901
self,
A: operators.BaseTransform,
b: NDArrayFloat,
iterations: int,
x0: Optional[NDArrayFloat] = None,
lower_limit: Union[float, NDArrayFloat, None] = None,
upper_limit: Union[float, NDArrayFloat, None] = None,
x_mask: Optional[NDArrayFloat] = None,
b_mask: Optional[NDArrayFloat] = None,
b_test_mask: Optional[NDArrayFloat] = None,
) -> tuple[NDArrayFloat, SolutionInfo]:
"""
Reconstruct the data, using the MLEM algorithm.
Parameters
----------
A : BaseTransform
Projection operator.
b : NDArrayFloat
Data to reconstruct.
iterations : int
Number of iterations.
x0 : Optional[NDArrayFloat], optional
Initial solution. The default is None.
lower_limit : Union[float, NDArrayFloat], optional
Lower clipping value. The default is None.
upper_limit : Union[float, NDArrayFloat], optional
Upper clipping value. The default is None.
x_mask : Optional[NDArrayFloat], optional
Solution mask. The default is None.
b_mask : Optional[NDArrayFloat], optional
Data mask. The default is None.
b_test_mask : Optional[NDArrayFloat], optional
Test data mask. The default is None.
Returns
-------
Tuple[NDArrayFloat, SolutionInfo]
The reconstruction, and the residuals.
"""
b = np.array(b)
(b_mask, b_test_mask) = self._initialize_b_masks(b, b_mask, b_test_mask)
# Back-projection diagonal re-scaling
b_ones = np.ones_like(b)
if b_mask is not None:
b_ones *= b_mask
tau = A.T(b_ones)
# Forward-projection diagonal re-scaling
x_ones = np.ones_like(tau)
if x_mask is not None:
x_ones *= x_mask
sigma = np.abs(A(x_ones))
sigma[(sigma / np.max(sigma)) < 1e-5] = 1
sigma = 1 / sigma
if x0 is None:
x = np.ones_like(tau)
else:
x = np.array(x0).copy()
if x_mask is not None:
x *= x_mask
self.data_term.assign_data(b)
info = SolutionInfo(self.info(), max_iterations=iterations, tolerance=self.tolerance)
if b_test_mask is not None or self.tolerance is not None:
Ax = A(x)
if b_test_mask is not None:
if self.data_term_test.background != self.data_term.background:
print("WARNING - the data_term and and data_term_test should have the same background. Making them equal.")
self.data_term_test.background = self.data_term.background
self.data_term_test.assign_data(b)
res_test_0 = self.data_term_test.compute_residual(Ax, mask=b_test_mask)
info.residual0_cv = self.data_term_test.compute_residual_norm(res_test_0)
if self.tolerance is not None:
res_0 = self.data_term.compute_residual(Ax, mask=b_mask)
info.residual0 = self.data_term.compute_residual_norm(res_0)
reg_info = "".join(["-" + r.info().upper() for r in self.regularizer])
algo_info = f"- Performing {self.upper()}-{self.data_term.upper()}{reg_info} iterations: "
for ii in tqdm(range(iterations), desc=algo_info, disable=(not self.verbose), leave=self.leave_progress):
info.iterations += 1
# The MLEM update
Ax = A(x)
if b_test_mask is not None:
res_test = self.data_term_test.compute_residual(Ax, mask=b_test_mask)
info.residuals_cv[ii] = self.data_term_test.compute_residual_norm(res_test)
if self.tolerance is not None:
res = self.data_term.compute_residual(Ax, mask=b_mask)
info.residuals[ii] = self.data_term.compute_residual_norm(res)
if self.tolerance > info.residuals[ii]:
break
if self.data_term.background is not None:
Ax = Ax + self.data_term.background
Ax = Ax.clip(eps, None)
upd = A.T(b / Ax)
x *= upd / tau
if lower_limit is not None or upper_limit is not None:
x = x.clip(lower_limit, upper_limit)
if x_mask is not None:
x *= x_mask
return x, info
[docs]
class SIRT(Solver):
"""
Initialize the SIRT solver class.
This class implements the Simultaneous Iterative Reconstruction Technique (SIRT) algorithm.
Parameters
----------
verbose : bool, optional
Turn on verbose output. The default is False.
leave_progress: bool, optional
Leave the progress bar after the computation is finished. The default is True.
tolerance : Optional[float], optional
Tolerance on the data residual for computing when to stop iterations.
The default is None.
relaxation : float, optional
The relaxation length. The default is 1.95.
regularizer : Sequence[regularizers.BaseRegularizer] | regularizers.BaseRegularizer | None, optional
Regularizer to be used. The default is None.
data_term : Union[str, data_terms.DataFidelityBase], optional
Data fidelity term for computing the data residual. The default is "l2".
data_term_test : Optional[data_terms.DataFidelityBase], optional
The data fidelity to be used for the test set.
If None, it will use the same as for the rest of the data.
The default is None.
"""
def __init__(
self,
verbose: bool = False,
leave_progress: bool = True,
relaxation: float = 1.95,
tolerance: Optional[float] = None,
regularizer: Union[Sequence[regularizers.BaseRegularizer], regularizers.BaseRegularizer, None] = None,
data_term: Union[str, data_terms.DataFidelityBase] = "l2",
data_term_test: Union[str, data_terms.DataFidelityBase, None] = None,
):
super().__init__(
verbose=verbose,
leave_progress=leave_progress,
relaxation=relaxation,
tolerance=tolerance,
data_term=data_term,
data_term_test=data_term_test,
)
self.regularizer = self._initialize_regularizer(regularizer)
[docs]
def info(self) -> str:
"""
Return the SIRT info.
Returns
-------
str
SIRT info string.
"""
reg_info = "".join(["-" + r.info().upper() for r in self.regularizer])
return Solver.info(self) + "-" + self.data_term.info() + reg_info
def __call__( # noqa: C901
self,
A: operators.BaseTransform,
b: NDArrayFloat,
iterations: int,
x0: Optional[NDArrayFloat] = None,
lower_limit: Union[float, NDArrayFloat, None] = None,
upper_limit: Union[float, NDArrayFloat, None] = None,
x_mask: Optional[NDArrayFloat] = None,
b_mask: Optional[NDArrayFloat] = None,
b_test_mask: Optional[NDArrayFloat] = None,
) -> tuple[NDArrayFloat, SolutionInfo]:
"""
Reconstruct the data, using the SIRT algorithm.
Parameters
----------
A : BaseTransform
Projection operator.
b : NDArrayFloat
Data to reconstruct.
iterations : int
Number of iterations.
x0 : Optional[NDArrayFloat], optional
Initial solution. The default is None.
lower_limit : Union[float, NDArrayFloat], optional
Lower clipping value. The default is None.
upper_limit : Union[float, NDArrayFloat], optional
Upper clipping value. The default is None.
x_mask : Optional[NDArrayFloat], optional
Solution mask. The default is None.
b_mask : Optional[NDArrayFloat], optional
Data mask. The default is None.
b_test_mask : Optional[NDArrayFloat], optional
Test data mask. The default is None.
Returns
-------
Tuple[NDArrayFloat, SolutionInfo]
The reconstruction, and the residuals.
"""
b = np.array(b)
(b_mask, b_test_mask) = self._initialize_b_masks(b, b_mask, b_test_mask)
# Back-projection diagonal re-scaling
b_ones = np.ones_like(b)
if b_mask is not None:
b_ones *= b_mask
tau = np.abs(A.T(b_ones))
for reg in self.regularizer:
tau += reg.initialize_sigma_tau(tau)
tau[(tau / np.max(tau)) < 1e-5] = 1
tau = self.relaxation / tau
# Forward-projection diagonal re-scaling
x_ones = np.ones_like(tau)
if x_mask is not None:
x_ones *= x_mask
sigma = np.abs(A(x_ones))
sigma[(sigma / np.max(sigma)) < 1e-5] = 1
sigma = 1 / sigma
if x0 is None:
x = np.zeros_like(x_ones)
else:
x = np.array(x0).copy()
self.data_term.assign_data(b, sigma)
info = SolutionInfo(self.info(), max_iterations=iterations, tolerance=self.tolerance)
if b_test_mask is not None or self.tolerance is not None:
Ax = A(x)
res_0 = self.data_term.compute_residual(Ax, mask=b_mask)
info.residual0 = self.data_term.compute_residual_norm(res_0)
if b_test_mask is not None:
if self.data_term_test.background != self.data_term.background:
print("WARNING - the data_term and and data_term_test should have the same background. Making them equal.")
self.data_term_test.background = self.data_term.background
self.data_term_test.assign_data(b, sigma)
res_test_0 = self.data_term_test.compute_residual(Ax, mask=b_test_mask)
info.residual0_cv = self.data_term_test.compute_residual_norm(res_test_0)
reg_info = "".join(["-" + r.info().upper() for r in self.regularizer])
algo_info = f"- Performing {self.upper()}-{self.data_term.upper()}{reg_info} iterations: "
for ii in tqdm(range(iterations), desc=algo_info, disable=(not self.verbose), leave=self.leave_progress):
info.iterations += 1
Ax = A(x)
res = self.data_term.compute_residual(Ax, mask=b_mask)
if b_test_mask is not None or self.tolerance is not None:
info.residuals[ii] = self.data_term.compute_residual_norm(res)
if b_test_mask is not None:
res_test = self.data_term_test.compute_residual(Ax, mask=b_test_mask)
info.residuals_cv[ii] = self.data_term_test.compute_residual_norm(res_test)
if self.tolerance is not None and self.tolerance > info.residuals[ii]:
if self.verbose:
print(f"Residual reached the desired tolerance of {self.tolerance}. Ending iterations..")
break
q = [reg.initialize_dual() for reg in self.regularizer]
for q_r, reg in zip(q, self.regularizer):
reg.update_dual(q_r, x)
reg.apply_proximal(q_r)
upd = A.T(res * sigma)
for q_r, reg in zip(q, self.regularizer):
upd -= reg.compute_update_primal(q_r)
x += upd * tau
if lower_limit is not None or upper_limit is not None:
x = x.clip(lower_limit, upper_limit)
if x_mask is not None:
x *= x_mask
return x, info
[docs]
class PDHG(Solver):
"""
Initialize the PDHG solver class.
PDHG stands for primal-dual hybrid gradient algorithm from Chambolle and Pock.
Parameters
----------
verbose : bool, optional
Turn on verbose output. The default is False.
leave_progress: bool, optional
Leave the progress bar after the computation is finished. The default is True.
tolerance : Optional[float], optional
Tolerance on the data residual for computing when to stop iterations.
The default is None.
relaxation : float, optional
The relaxation length. The default is 0.95.
regularizer : Sequence[regularizers.BaseRegularizer] | regularizers.BaseRegularizer | None, optional
Regularizer to be used. The default is None.
data_term : Union[str, data_terms.DataFidelityBase], optional
Data fidelity term for computing the data residual. The default is "l2".
data_term_test : Optional[data_terms.DataFidelityBase], optional
The data fidelity to be used for the test set.
If None, it will use the same as for the rest of the data.
The default is None.
"""
def __init__(
self,
verbose: bool = False,
leave_progress: bool = True,
tolerance: Optional[float] = None,
relaxation: float = 0.95,
regularizer: Union[Sequence[regularizers.BaseRegularizer], regularizers.BaseRegularizer, None] = None,
data_term: Union[str, data_terms.DataFidelityBase] = "l2",
data_term_test: Union[str, data_terms.DataFidelityBase, None] = None,
):
super().__init__(
verbose=verbose,
leave_progress=leave_progress,
relaxation=relaxation,
tolerance=tolerance,
data_term=data_term,
data_term_test=data_term_test,
)
self.regularizer = self._initialize_regularizer(regularizer)
[docs]
def info(self) -> str:
"""
Return the PDHG info.
Returns
-------
str
PDHG info string.
"""
reg_info = "".join(["-" + r.info().upper() for r in self.regularizer])
return Solver.info(self) + "-" + self.data_term.info() + reg_info
@staticmethod
def _initialize_data_fidelity_function(data_term: Union[str, data_terms.DataFidelityBase]):
if isinstance(data_term, str):
if data_term.lower() == "l2":
return data_terms.DataFidelity_l2()
if data_term.lower() == "l1":
return data_terms.DataFidelity_l1()
if data_term.lower() == "kl":
return data_terms.DataFidelity_KL()
else:
raise ValueError(f'Unknown data term: "{data_term}", accepted terms are: "l2" | "l1" | "kl".')
else:
return cp.deepcopy(data_term)
[docs]
def power_method(
self, A: operators.BaseTransform, b: NDArrayFloat, iterations: int = 5
) -> tuple[np.floating, Sequence[int], DTypeLike]:
"""
Compute the l2-norm of the operator A, with the power method.
Parameters
----------
A : BaseTransform
Operator whose l2-norm needs to be computed.
b : NDArrayFloat
The data vector.
iterations : int, optional
Number of power method iterations. The default is 5.
Returns
-------
Tuple[float, Tuple[int], DTypeLike]
The l2-norm of A, and the shape and type of the solution.
"""
x: NDArrayFloat = np.array(np.random.rand(*b.shape))
x = x.astype(b.dtype)
x /= np.linalg.norm(x)
x = A.T(x)
x_norm = np.linalg.norm(x)
L = x_norm
for _ in range(iterations):
x /= x_norm
x = A.T(A(x))
x_norm = np.linalg.norm(x)
L = np.sqrt(x_norm)
return (L, x.shape, x.dtype)
def _get_data_sigma_tau_unpreconditioned(self, A: operators.BaseTransform, b: NDArrayFloat):
(L, x_shape, x_dtype) = self.power_method(A, b)
tau = L
dummy_x = np.empty(x_shape, dtype=x_dtype)
for reg in self.regularizer:
tau += reg.initialize_sigma_tau(dummy_x)
tau = self.relaxation / tau
sigma = self.relaxation / L
return (x_shape, x_dtype, sigma, tau)
def __call__( # noqa: C901
self,
A: operators.BaseTransform,
b: NDArrayFloat,
iterations: int,
x0: Optional[NDArrayFloat] = None,
lower_limit: Union[float, NDArrayFloat, None] = None,
upper_limit: Union[float, NDArrayFloat, None] = None,
x_mask: Optional[NDArrayFloat] = None,
b_mask: Optional[NDArrayFloat] = None,
b_test_mask: Optional[NDArrayFloat] = None,
precondition: bool = True,
) -> tuple[NDArrayFloat, SolutionInfo]:
"""
Reconstruct the data, using the PDHG algorithm.
Parameters
----------
A : BaseTransform
Projection operator.
b : NDArrayFloat
Data to reconstruct.
iterations : int
Number of iterations.
x0 : Optional[NDArrayFloat], optional
Initial solution. The default is None.
lower_limit : Union[float, NDArrayFloat], optional
Lower clipping value. The default is None.
upper_limit : Union[float, NDArrayFloat], optional
Upper clipping value. The default is None.
x_mask : Optional[NDArrayFloat], optional
Solution mask. The default is None.
b_mask : Optional[NDArrayFloat], optional
Data mask. The default is None.
b_test_mask : Optional[NDArrayFloat], optional
Test data mask. The default is None.
precondition : bool, optional
Whether to use the preconditioned version of the algorithm. The default is True.
Returns
-------
Tuple[NDArrayFloat, SolutionInfo]
The reconstruction, and the residuals.
"""
b = np.array(b)
if precondition:
try:
At_abs = A.T.absolute()
A_abs = A.absolute()
except AttributeError:
print(A)
print("WARNING: Turning off preconditioning because system matrix does not support absolute")
precondition = False
(b_mask, b_test_mask) = self._initialize_b_masks(b, b_mask, b_test_mask)
if precondition:
tau = np.ones_like(b)
if b_mask is not None:
tau *= b_mask
tau = np.abs(At_abs(tau))
for reg in self.regularizer:
tau += reg.initialize_sigma_tau(tau)
tau[(tau / np.max(tau)) < 1e-5] = 1
tau = self.relaxation / tau
x_shape = tau.shape
x_dtype = tau.dtype
sigma = np.ones_like(tau)
if x_mask is not None:
sigma *= x_mask
sigma = np.abs(A_abs(sigma))
sigma[(sigma / np.max(sigma)) < 1e-5] = 1
sigma = self.relaxation / sigma
else:
(x_shape, x_dtype, sigma, tau) = self._get_data_sigma_tau_unpreconditioned(A, b)
if x0 is None:
x0 = np.zeros(x_shape, dtype=x_dtype)
else:
x0 = np.array(x0).copy()
x = x0
x_relax = x.copy()
self.data_term.assign_data(b, sigma)
p = self.data_term.initialize_dual()
q = [reg.initialize_dual() for reg in self.regularizer]
info = SolutionInfo(self.info(), max_iterations=iterations, tolerance=self.tolerance)
if b_test_mask is not None or self.tolerance is not None:
Ax = A(x)
res_0 = self.data_term.compute_residual(Ax, mask=b_mask)
info.residual0 = self.data_term.compute_residual_norm(res_0)
if b_test_mask is not None:
if self.data_term_test.background != self.data_term.background:
print("WARNING - the data_term and and data_term_test should have the same background. Making them equal.")
self.data_term_test.background = self.data_term.background
self.data_term_test.assign_data(b, sigma)
res_test_0 = self.data_term_test.compute_residual(Ax, mask=b_test_mask)
info.residual0_cv = self.data_term_test.compute_residual_norm(res_test_0)
reg_info = "".join(["-" + r.info().upper() for r in self.regularizer])
algo_info = f"- Performing {self.upper()}-{self.data_term.upper()}{reg_info} iterations: "
for ii in tqdm(range(iterations), desc=algo_info, disable=(not self.verbose), leave=self.leave_progress):
info.iterations += 1
Ax_rlx = A(x_relax)
self.data_term.update_dual(p, Ax_rlx)
self.data_term.apply_proximal(p)
if b_mask is not None:
p *= b_mask
for q_r, reg in zip(q, self.regularizer):
reg.update_dual(q_r, x_relax)
reg.apply_proximal(q_r)
upd = A.T(p)
for q_r, reg in zip(q, self.regularizer):
upd += reg.compute_update_primal(q_r)
x_new = x - upd * tau
if lower_limit is not None or upper_limit is not None:
x_new = x_new.clip(lower_limit, upper_limit)
if x_mask is not None:
x_new *= x_mask
x_relax = x_new + (x_new - x)
x = x_new
if b_test_mask is not None or self.tolerance is not None:
Ax = A(x)
res = self.data_term.compute_residual(Ax, mask=b_mask)
info.residuals[ii] = self.data_term.compute_residual_norm(res)
if b_test_mask is not None:
res_test = self.data_term_test.compute_residual(Ax, mask=b_test_mask)
info.residuals_cv[ii] = self.data_term_test.compute_residual_norm(res_test)
if self.tolerance is not None and self.tolerance > info.residuals[ii]:
if self.verbose:
print(f"Residual reached the desired tolerance of {self.tolerance}. Ending iterations..")
break
return x, info