WSClean version 2.9
===================

Released 2020-03-27

WSClean 2.9 is released together with `IDG version 0.7 <https://gitlab.com/astron-idg/idg/-/tags/0.7>`_.

Summary of changes: WSClean+IDG is now much faster, in particular with fast-changing aterms.  The combination of WSClean 2.9 + IDG 0.7 supports the efficient use of GPUs to grid large data volumes with complex a-terms. Furthermore, a new gridder that is more accurate compared to the default w-stacking gridder, and for some cases also faster! (in particular large images, many visibilities). The plan is also to move WSClean to Github in the next version of thereafter.

Major & visible changes:

* Add new gridder ":doc:`wgridder <../wgridding>`", a stand-alone gridder written by Martin Reinecke that is now integrated in WSClean.
* Applying a second aterm to all antennas is possible by setting dimension of antenna axis to one in aterm fits file.
* Make source list output possible in IDG.
* The FFTs are now performed with floats instead of doubles, thereby descreasing memory usage by 2 and increasing the speed anywhere from 20-100%.
* LOFAR image-based beam correction (i.e. no aterm correction) now uses full Mueller matrix calculations instead of Jones, which removes some biases in beam correction that were seen.
* New options ``-reuse-psf`` and ``reuse-dirty`` to skip these steps when they already exist.
* WSClean makes use of IDG's API changes to allocate optimal buffer sizes, greatly increasing the speed of IDG, and solving allocation problems on low-mem platforms
* When parallel deconvolution is used, the logging is now much improved: only one thread reports its full progress.
* Correct smallest multi-scale scale when using Gaussian tapering. Multi-scale cleaning was using just the longest baseline for determining the smallest scale to clean with. This causes tapered imaging to almost never use the smallest scale.
* Add a 'dry run' mode, requested by J. Morgan. Fixes #162.

Bug fixes & other changes:

* Stokes V imaging with R/L pols results in zero image (reported by Chiara Stuardi)
* Don't allow direct MS access for multi spw sets, to prevent a deadlock.
* Output error when trying to combine parallelgridding with IDG.
* Don't incorrectly apply the average beam when using idg + apply-primary-beam.
* Support newer casacore versions.
* Remove dependency on boost thread.
* Image the gridding kernel as option was removed, as both IDG and WGridder don't support it.
* Fix beam calculation for 1 timestep mses
* Fix a crash when using pb correction + deconvolution channels
* Solve reported problem with HDF5/Intel compilation
