ChangeLog

0.30.0:
- sht:
    - new function `pseudo_analysis_general` for iterative least-squares analyis
      of spherical maps on rbitrry grids


0.29.0:
- general:
    - rework multi-threading infrastructure to allow integration with external
      thread pool implementations.
    - make more extensive use of uninitialized arays. This helps performance
      and scaling, especially for small SHTs.

- fft:
    - add the functions `r2r_separable_fht` and `r2r_genuine_fht`, which perform
      Hartley transforms using the commonly adopted convention, i.e.
          FHT(x) = FFT(x).real - FFT(x).imag
      instead of the unusual convention of `r2r_separable_hartley` and
      `r2r_genuine_hartley`, which use
          FHT(x) = FFT(x).real + FFT(x).imag
      `r2r_separable_hartley` and `r2r_genuine_hartley` should not be used in
      new code, but they are kept for backwards compatibility.

- sht:
    - new functions `synthesis_general` and `adjoint_synthesis_general`
      for SHTs on maps without any constraint on pixel locations.
      This allows, for example, using maps whose pixel positions have been
      distorted by lensing, or QuadCube maps.
    - functions `synthesis`, `adjoint_synthesis`, `synthesis_deriv1`,
      and `pseudo_analysis`: introduce an optional integer parameter `mmax`
      and allow it to be different from `lmax` (`mmax==lmax` was implicitly
      assumed so far)

- nufft:
    - re-write core part of the 2D Type 1 NUFFT, which was miscompiled on some
      platforms. Unfortunately, the new implementation is slightly slower on
      x86-64.
    - allow very small uniform grid dimensions (down to 1)

- wgridder:
    - allow very small uniform grid dimensions (down to 2)

- misc:
    - new function `empty_noncritical` for building empty numpy arrays without
      critical strides


0.28.0:
- general:
    - allow control over multithreading via environment variables
      DUCC0_NUM_THREADS, DUCC0_PIN_DISTANCE, and DUCC0_PIN_OFFSET.
      This is still experimental and may change in the future.

- fft:
    - introduce a flag `allow_overwriting_input` to `c2r`, which can speed up
      execution by avoiding temporary arrays

- nufft/wgridder:
    - changed kernel database to hold optimized kernels depending on
      dimensionality and floating point accuracy. This allows for slightly
      better tuning and improves maximum attainable accuracy in 2D and 3D.

- julia:
    - start of a Julia wrapper, currently focused on FFT, NUFFT and SHT support

- math:
    - computations involving Peano-Hilbert indices are now much faster 

- misc:
    - new function `roll_resize_roll`, which allows efficient combined
      rolling/padding/truncation of arrays.


0.27.0:
- general:
  - modernize CI and build machinery
  - some code was moved from header files into .cc files to avoid duplicate
    symbols in some situations.

- nufft:
  - added a "plan" class, which allows efficient repeated execution of a
    transform with fixed grid geometry and nonuniform point positions.
    (For transforms that are only executed once, the traditional interface
    should be preferred.)
  - added new parameters for data periodicity (formerly hardwired to 2pi) and
    data ordering on the regular grids (formerly starting with the most negative
    frequency, now also allows "standard" FFT ordering starting with the zero
    mode).
  - added a benchmark demo script for easier comparison to FINUFFT and NFFT.jl.


0.26.0:
- general:
  - clarify that the preferred installation method is compilation from source

- wgridder:
  - add "self-tuning" versions of `vis2dirty` and `dirty2vis` which attempt to
    save time by
     - splitting visibilities into a small-w and large-w part and processing
       them separately, and/or
     - subdividing the field of view into facets.
    This can be advantageous when FFT cost would dominate using the naive
    approach and the number of w-planes is large (roughly 50 and higher).

- sht:
  - the methods synthesis, adjoint_synthesis, and synthesis_deriv1 now accept
    an optional leading dimension in the alm/map arrays, to allow "batched"
    transforms. If the batch size is large enough, parallelization will not
    be done within a single transforms, but rather over different transforms,
    which can be beneficial, especially if the transforms are small.
  - a new method "pseudo_analysis" was added, which performs iterative,
    approximate map analysis using the LSMR algorithm.


0.25.0:
- general:
  - try to fix the package on 32bit platforms

- nufft:
  - significant performance and accuracy improvements

- wgridder:
  - recalculated kernels, improved error model
  - small performance tweaks


0.24.0:
- general:
  - work around a compilation problem with gcc 7

- nufft:
  - beginnings of a non-uniform FFT module
    Conventions are closely following the FINUFFT library.
    The interface is not finalized yet.

- wgridder:
  - improved pre-sorting of visibilities


0.23.0:
- general:
  - improved template code for multi-array operations (internal detail)

- fft:
  - fix a bug in multi-D Hartley transform which was introduced in ducc0 0.21.
    This bug was triggered in cases with two or three transformed axes and at
    least one untransformed axis.
  - use clear dual-license headers in all files required for the FFT component

- healpix:
  - input arrays to all functions can now be float32/int32 as well

- wgridder:
  - performance tweaks to FFT and kernel evaluation parts; performance gain
    on the order of 10%.


0.22.0:
- general:
  - many internal cleanups and consistency improvements
  - preparations for release as an Alpine Linux package

- fft:
  - re-introduce plan caching. This is possible since plans for large 1D
    transforms no longer scale with the length of the transform,but only its
    square root, limiting the memory overhead
  - code tweaks to improve copying steps for multi-D transforms (basically a
    workaround for mis-optimizations by gcc)


0.21.0:
- general:
  - support for more platforms (e.g. Raspberry Pi)
  - rewrite of the classes for multidimensional array views, which allows
    many simplifications, multithreading etc.

- fft:
  - low-level tweaks which accelerate internal function calls; this especially
    helps multi-D transforms with short axis lengths
  - genuine Hartley transforms over 2 and 3 axes no longer require big temporary
    arrays

- healpix:
  - multithreading support for most functions


0.20.0:
- general:
  - minimum required Python version is now 3.7
  - tests: retire Ubuntu 18, improve tests with icpx
  - fix compilation failure on non-x86 platforms

- fft:
  - allow individual, compile-time, selection of SIMD types to be used

- sht/healpix:
  - prepare better support for Healpix pixelization

- misc:
  - convenience function for building numpy arrays without critical strides


0.19.0:
- general:
  - binary wheels can now be built and uploaded to PyPI; the installation
    instructions have been updated accordingly. Please provide feedback in case
    of problems!

- fft:
  - C++ sources for FFT calculation now have their own subdirectory.
  - new function `r2r_fftw`, which supports FFTW's halfcomplex storage scheme.
  - new function `convolve_axis`, which performs efficient convolution of arrays
    with arbitrary 1D kernels, optionally followed by zero-padding/truncation.


0.18.0:
- sht:
  - implement adoint_analysis
    CAUTION: this is still really experiental!

- wgridder:
  - improve cost model, assuming that the FFT component will not scale perfectly


0.17.0:
- general:
  - more information available on PyPI

- fft:
  - performance tweaks for 1D FFTs
  - reduced memory overhead for 1D FFTs
  - multithreading support for 1D FFTs (this is only advantageous for very long
    transforms at the moment)

- sht:
  - interface for fully general SHTs is now accessible from Python; this is not
    completely finalized, however.
  - improved a_lm rotation performance


0.16.0:
- general:
  - the GIL is now released in many more functions

-fft:
  - very long 1D transforms now have a lower memory overhead and should be
    faster

-sht:
  - a_lm rotation is now much more accurate, but slightly slower
  - the improved spherical harmonic analysis capabilities are now documented

-misc:
  - two new convenience functions vdot() and l2error() were added


0.15.0:
- general:
  - the code is now compiled with the "-fvisibility=hidden" flag, which reduces
    the size of the resulting binary.
  - demo codes were adjusted to use the new SHT interface.

- fft:
  - added some functions to reduce the amount of unnecessary memory
    allocations and data copying.

- sht:
  - it is no longer necessary to pre-allocate an array for the output of the
    `sht.experimental.*2d*` functions. If not provided, the functions will
    create the array automatically now, which requires passing of new `ntheta`
    and `nphi` parameters in come cases.
  - the `sht.experimental.*2d*` functions now take an optional `mmax` parameter
    which can be used to limit the maximum azimuthal moment of a transform.
    If not supplied, the code assumes that `mmax` is equal to `lmax`.
  - added some unit tests for the new SHT interface.
  - reduced memory overhead forsome of the `sht.experimental.*2d*` functions.

- misc:
  - added functionality (originally from Planck Level-S) to simulate time
    streams of detector noise.


0.14.0:
- general:
  - ducc0.__version__ is now also defined under Windows

- sht:
  - further performance improvements
  - added functions for manipulation of "2D maps", i.e. maps consisting of
    (ntheta*nphi) pixels with equidistant pixels in phi, and rings distributed
    along theta according to one of the CC, DH, F1, F2, GL, MW, MWflip schemes.

- totalconvolve:
  - bug fix in the adjoint convolution: results were inadvertently conjugated


0.13.0:
- general:
  - more comprehensive references in README.md

- sht:
  - bug fixes
  - tweaks to the experimental interface for extracting moments up to lmax
    from maps with only lmax+1 or lmax+2 equidistant rings.


0.12.0:
- general:
  - update installation instructions in README.md

- sht:
  - expose functionality for computing gradient maps from spherical harmonic
    coefficients


0.11.0:
- general:
  - beginning of Doxygen documentation for the C++ part
  - fixes to the #include statements in header files; now every header can be
    included in isolation.
  - some CI streamlining


0.10.0:
- general:
  - HTML documentation generation using Sphinx
    Up-to-date documentation for the ducc0 branch is available at
    https://mtr.pages.mpcdf.de/ducc/.
  - more and improved docstrings
  - SIMD datatypes are now much more compatible with C++ upcoming SIMD types.
    The code can be compiled with the types from <experimental/simd> if
    available, with very small manual changes.
  - reshuffling and renaming of files

- fft:
  - 1D transforms have been rewritten using a much more flexible class hierarchy
    which allows more optimizations. For example 1D FFTs can now be partially
    multi-threaded and the Bluestein algorithm can be used as a single pass
    instead of just replacing a whole transform.

- sht:
  - design of a new SHT interface. Parts of this interface are made visible
    from Python, in the "sht.experimental" submodule. The "sharpjob_d"-based
    interface will be kept for compatibility purposes until ducc1 is released.
  - experimental support for spherical harmonic analysis that only requires
    lmax+1 or lmax+2 equidistant rings for exact analysis up to lmax.
  - misc.rotate_alm was moved to the sht submodule.

- totalconvolver:
  - interface change to synchronize it better with the upcoming SHT interface.
    Basically, if an array has a "number of components" axis, this is now
    always in first place.
    Strictly speaking this is an interface-breaking change, but to the best of
    my knowledge the interface in question has not been used in other projects
    yet.


0.9.0:
- general:
  - improved and faster computation of Gauss-Legendre nodes and weights
    using Ignace Bogaert's implementation (https://doi.org/10.1137/140954969,
    https://sourceforge.net/projects/fastgausslegendrequadrature/)
  - Intel OneAPI compilers are now supported
  - new accepted value "none-debug" for DUCC0_OPTIMIZATION

- wgridder:
  - fixed a bug which could cause memory accesses beyond the end of an array

- fft:
  - slightly improved buffer re-use

- misc:
  - substantially faster a_lm rotation code based on the Mikael Slevinsky's
    FastTransforms package (https://github.com/MikaelSlevinsky/FastTransforms)


0.8.0:
- general:
  - compiles and runs on MacOS 11
  - choice of various optimization and debugging levels by setting
    the DUCC0_OPTIMIZATION variable before compilation.
    Valid choices are
    "none":
      no optimization or debugging, fast compilation
    "portable":
      Optimizations which are portable to all CPUs of a given family
    "portable-debug":
      same as above, with debugging information
    "native":
      Optimizations which are specific to the host CPU, non-portable library
    "native-debug":
      same as above, with debugging information
    Default is "native".

- wgridder:
  - more careful treatment of u,v,w-coordinates and phase angles, leading to
    better achievable accuracies for single-precision runs
  - performance improvements by making the computed interval in "n-1" symmetric
    around 0. This reduces the number of required w planes significantly.
    Speedups are bigger for large FOVs and when FFT is dominating.
  - allow working with dirty images that are shifted with respect to the phase
    center. This can be used for faceting and incorporating DDEs.
  - new optional flag "double_precision_accumulation" for gridding routines,
    which causes accumulation onto the uv grid to be done in double precision,
    regardless of input and output precision. This can be helpful to avoid
    accumulation errors in special circumstances.

- pointingprovider:
  - improved performance via vectorized trigonometric functions


0.7.0:
- general:
  - compilation with MSVC on Windows is now possible

- wgridder:
  - performance (especially scaling) improvements
  - oversampling factors up to 2.5 supported
  - new, more flexible interface in submodule `wgridder.experimental`
    (subject to further changes!)

- totalconvolver:
  - now performs non-equidistant FFT interpolation also in psi direction,
    making it much faster for large kmax.
  - new low-level interface which allows flexible re-distribution of work
    over MPI tasks (responsibility of the caller)


0.6.0:
- general:
  - multi-threading improvements contributed by Peter Bell

- wgridder:
  - new, smaller internal data structure


0.5.0:
- wgridder:
  - internally used grid size is now chosen automatically, and the parameters
    "nu" and "nv" are ignored; they will be removed in ducc1.


0.3.0:
- general:
  - The package should now be installable from PyPI via pip even on MacOS.
    However, MacOS >= 10.14 is required.

- wgridder:
  - very substantial performance and scaling improvements


0.2.0:
- wgridder:
  - kernels are now evaluated via polynomial approximation, allowing much
    more freedom in the choice of kernel function
  - switch to 2-parameter ES kernels for better accuracy
  - unnecessary FFT calculations are skipped

- totalconvolve:
  - improved accuracy by making use of the new wgridder kernels
  - *INTERFACE CHANGE* removed method "epsilon_guess()"

- pointingprovider:
  new, experimental module for computing detector pointings from a time stream
  of satellite pointings. To be used by litebird_sim initially.