Changelog

2.0.0 (TBD)

Breaking Changes

• Python ≥ 3.12 required (dropped support for 3.9, 3.10, 3.11)

• New required dependency: parallelproj-core >= 2.0.5 — the compiled C/CUDA projection kernels have been extracted into a separate conda-forge package (parallelproj-core). The old shared-library loading via ctypes is gone.

• Low-level projection functions moved to parallelproj_core: joseph3d_fwd, joseph3d_back, and all TOF variants (e.g. joseph3d_fwd_tof_sino) are no longer in the parallelproj namespace. Import them from parallelproj_core instead. Note that the TOF function names were also reordered (e.g. joseph3d_fwd_tof_sino → joseph3d_tof_sino_fwd).

• Top-level namespace reduced: only Array, empty_cuda_cache, to_numpy_array, and count_event_multiplicity are exported from parallelproj directly. All other classes must now be imported from their submodules:

  from parallelproj.operators import LinearOperator
  from parallelproj.projectors import RegularPolygonPETProjector
  from parallelproj.pet_scanners import RegularPolygonPETScannerGeometry
  from parallelproj.pet_lors import RegularPolygonPETLORDescriptor
  

• Runtime-detection variables removed from the parallelproj namespace: cuda_present, cupy_enabled, torch_enabled, num_visible_cuda_devices, lib_parallelproj_c_fname, lib_parallelproj_cuda_fname, cuda_kernel_file, is_cuda_array. Use parallelproj_core.cuda_enabled for CUDA detection.

• ``RegularPolygonPETLORDescriptor`` signature changed: max_ring_difference parameter replaced by a michelogram parameter that accepts a Michelogram object. See new Michelogram class below.

• ``TOFNonTOFElementwiseMultiplicationOperator`` removed.

• ``MatrixOperator.iscomplex`` and ``ElementwiseMultiplicationOperator.iscomplex`` changed from method to property: replace op.iscomplex() calls with op.iscomplex.

• ``GradientFieldProjectionOperator`` numeric change: the eta normalisation formula was corrected (sqrt(sum(g²) + η²) instead of sqrt(sum(g² + η²))). Results will differ from v1.x.

• License changed from MIT to Apache-2.0.

• scipy >= 1.15 now required (was ~=1.0).

• array-api-compat >= 1.7 now required.

• Import-time banner and PARALLELPROJ_SILENT_IMPORT environment variable removed; import parallelproj is now silent.

New Features

• ``parallelproj.functions`` submodule: new module providing abstract base classes (C1Function, C2Function, FunctionWithProx, FunctionWithConjProx) and concrete loss/regularisation implementations for optimisation:

  • NegPoissonLogL, NegPoissonLogLSafe — Poisson log-likelihood (sinogram and masked variants)

  • NegPoissonLogLListmode — listmode Poisson log-likelihood with built-in forward model

  • HalfSquaredL2Deviation — weighted least-squares deviation

  • SumC1Function / SumC2Function — also created via f1 + f2 operator overloading

  • C1AffineObjective / C2AffineObjective — compose a loss with an affine forward model

  • NonNegativeIndicator — non-negativity constraint with proximal operator

  • MixedL21Norm — mixed L2,1 norm for group sparsity / TV-type regularisation

• ``Michelogram`` class (parallelproj.pet_lors): encapsulates the full axial plane layout for cylindrical PET scanners under odd-span compression, including ring-pair-to-plane tables and visualisation methods.

• ``SinogramAxialCompressionOperator`` (parallelproj.pet_lors): LinearOperator that axially compresses a span-1 sinogram to a higher odd span (mode="sum" or mode="average").

• ``LinearOperator.H`` property and ``AdjointLinearOperator`` class: obtain the adjoint of any operator via A.H.

• ``EqualBlockPETProjector`` ``num_chunks`` parameter: split block-pair projections into chunks to reduce peak GPU memory usage.

• ``RegularPolygonPETProjector.convert_sinogram_to_listmode`` gained a shuffle parameter to randomly permute the returned event list.

• ``VstackOperator`` now raises ValueError on inconsistent in_shape across stacked operators (previously silent).

• ``parallelproj.__version__`` is now exposed at the top level.

1.10.2 (Aug 20, 2025)

• add compatibility for latest cupy version (>= 13.5) which require from_dlpack to convert from torch tensors

• fix minor issues to be compatible with array-api-strict~=2.0

1.10.1 (Jan 15, 2025)

• add a check whether sum of tof bins along LOR is non-zero before running TOF sinogram back projector

• update installation instructions after conda-forge recipe was updated

• clean up RTD docs build

1.10.0 (July 29, 2024)

• add support for numpy>=2.0

• add tests with numpy 2.0 on python 3.9 and 3.12

• remove tox.ini

1.9.1 (June 19, 2024)

• BUGFIX: add missing device in BlockPET LOR descriptor (needed for pytorch + cuda backend)

1.9 (June 18, 2024)

• add functionality to create scanners, LOR descriptors and projectors for scanners consisting of equal “block” modules

• BUGFIX: correct behavior of TOF kernel truncation which was wrong in the case that the tof bin width was >> tof resolution

1.8 (March 20, 2024)

• add function to count event multiplicity

• add more examples (e.g. DePierro and LM SPDHG)

• re-organize folder structure and pyproject.toml

• force array-api-compat<1.5 (bug in 1.5.0)

• use array-api-strict instead of numpy.array_api

1.7.3 (January 26, 2024)

• print banner

• test also on Windows

1.7.2 (January 26, 2024)

• require python>=3.9

• replace distuils.spawn by shutil.which

1.7.1 (January 19, 2024)

• BUGFIX: correct bug in the “chunking” of TOF sinogram projections in the python interface

1.7.0 (January 15, 2024)

• update of documentation

• addition of more examples

• addition of high-level classes for RegularPolygonPETScanner and LOR descriptors

1.6.2 (December 01, 2023)

• BUGFIX: correct use of conj() of scalar value to be array api compatible

• BUGFIX: divided by float() to be array api compatible

• add scipy dependency

1.6.1 (October 18, 2023)

• BUGFIX: add sigma as explicit argument in GaussianFilterOperator and convert correctly to numpy/cupy arrays

1.6.0 (October 16, 2023)

• rewrite LinearOperator base class to support python array api including devices

• add missing type hints

• add finite difference operator

• remove obsolete functions

1.5.0 (July 29, 2023)

• add compatibility of python wrapper to python array api (via array-api-compat) such that numpy, cupy, pytorch arrays can be directly projected

• no changes to the C/CUDA libs

1.4.0 (June 11, 2023)

• add Linear Operators

1.3.7 (April 27, 2023)

• update documentation

1.3.6 (April 25, 2023)

• enable readthedocs

1.3.5 (April 23, 2023)

• add py.typed for mypy type checker

1.3.4 (April 21, 2023)

• rename python binding back to parallelproj

1.3.3 (April 20, 2023)

• import annotations from __future__ to be compatible with older versions

1.3.2 (April 18, 2023)

• rename test folder

• lower absolute tolerance for forward TOF tests (otherwise windows builds might fail)

1.3.1 (April 17, 2023)

• add num_visible_devices definition when cuda is not present

1.3.0 (April 17, 2023)

• clean up pyproject.toml

• move tests and rename imports in tests

• rename python package to parallelprojpy and adapt setup.cfg

• add first version of pyproject.toml

1.2.16 (April 16, 2023)

• improve way to detect whether visible GPUs are present in the python API

• remove AS approximation of erff in openMP lib (too large inaccuracies)

• add TOF LM tests

• add listmode wrappers

• add TOF sino fwd test

1.2.15 (April 15, 2023)

• add TOF sino projector wrappers and first test

• BUGFIX: correct start and stop of loop over planes in cuda TOF sino projector when direction=2

• add adjointness test (indirect test for back projection)

• add first python unit test for non-tof fwd projection

• add first python wrappers for non-tof Joseph projectors

1.2.14 (February 15, 2023)

• make target link libraries (m and OpenMP) private

1.2.13 (January 13, 2023)

• fix variable expansion in Config.cmake.in

• update README

• add link to arxiv preprint

1.2.12 (January 08, 2023)

• set CUDA_HOST_COMPILER only when using clang

• skip build of cuda lib if cuda is not present

1.2.11 (January 05, 2023)

• set default CMAKE_CUDA_HOST_COMPILER to CMAKE_CXX_COMPILER

1.2.10 (December 30, 2022)

• link parallelproj_c against libm (using PUBLIC link interface)

• use better way to test whether we have to link against libm

• add adjoint back projection test

• add more generic non-tof test that tests rays in all 3 directions

1.2.9 (December 09, 2022)

• BUGFIX: correct calculation of x_pr2 when principal direction is 0

1.2.8 (December 02, 2022)

• do not install test binaries

• require CXX compiler only for CUDA

1.2.6 (November 18, 2022)

• clean up CMake logic

1.2.5 (November 11, 2022)

• add conditions to nested if-else when adding cuda subdir

1.2.4 (November 10, 2022)

• add fatal error if cuda lib is to be built but no cuda compiler is found

1.2.3 (November 04, 2022)

• add skip option for cmake

1.2.2 (November 03, 2022)

• read version from package.json

• add conda build