Ligo.skymap

===================

- Fix a regression that caused ``ligo-skymap-flatten`` to fail for 2D sky maps.

===================

- Add installation instructions for both pip and conda.

- Introduce the :mod:`ligo.skymap.postprocess.crossmatch` module for fast
cross-matching of sky maps with galaxy redshift catalogs.

This module used to be named :mod:`ligo.skymap.postprocess.find_injection`
because it was originally designed for recovering injections (simulated
signals) from sky localization simulations. We changed the name because
galaxy cross matching is probably a more common use case than injection
finding.

The :func:`~ligo.skymap.postprocess.crossmatch.crossmatch` method also got
some performance improvements for cross matching of large numbers of targets.
Previously, to process :math:`n` targets, it took about :math:`(4 + 0.008 n)`
seconds --- for a catalog of 300k targets, about 40 minutes. Now, it takes
about 4 seconds total regardless of the number of targets.

Note that the :mod:`ligo.skymap.postprocess.crossmatch` API is likely to
change as documentation for it improves.

- Several performance improvements for BAYESTAR:

- Add GCC branch prediction hints.

- Exploit nested parallelism in radial integrator lookup table generation.

- Calculate signal amplitudes using single-precision floating point.

- Add tracepoints for Intel's Instrumentation and Tracing Technology (ITT)
API, which can be enabled at build time by passing the ``--with-ittnotify``
option to ``python setup.py build``.

==================

- Switch from using the GNU Compiler Collection (gcc) to the Intel C Compiler
(icc) for building optimized Linux binaries. On Intel Skylake machines, this
can speed up BAYESTAR by 1.3x or more.

Due to icc's C ABI requirements, Linux wheels now target the `manylinux2010
<https://www.python.org/dev/peps/pep-0571/>`_ platform tag.

- In BAYESTAR, change the OpenMP scheduling kind from ``static`` (the default)
to ``guided``. This improves CPU utilization by load-balancing work across
threads more efficiently.

==================

- Add ``ligo-skymap-constellations``, an easter egg program to list the most
probable constellations for a localization, for fun and for public outreach
purposes.

- Switch the implementation of the ``smooth`` option of ``imshow_hpx`` and
``contour_hpx`` from ``scipy.ndimage.gaussian_filter`` to
``astropy.convolution.convolve_fft`` in order to correctly handle points near
the projection boundary where invalid values must be masked out.

- Register ``AutoScaledWCSAxes`` as a Matplotlib projection with the name
``astro wcs`` so that subclasses can be created using
``plt.axes(..., projection='astro wcs', header='...')``.

- Suppress Numpy warnings for HEALPix reprojection operations in WCS plots
because it is normal for invalid values to occur when transforming pixels
that lie outside of the projection.

- Add ``rotate`` option to ``astro globe``, ``geo globe``, and ``astro zoom``
to rotate the plot in the plane of the screen about the center of the
projection.

- Pass through keyword arguments from ``AutoScaledWCSAxes.scalebar()`` and
``AutoScaledWCSAxes.scalebar().label()`` to Matplotlib so that plot styles
can be adjusted easily.

- Bump matplotlib version to >= 3.0.2 because of a bug that affected
``ligo-skymap-plot-stats``.

- The ``ligo-skymap-unflatten`` tool will now write multiresolution sky maps
with pixels sorted by the ``UNIQ`` column, as required by the standard
multi-order coverage map serialization in FITS.

- All functions in ``ligo.skymap.moc`` now assume that ``uniq`` is a signed
integer. This makes it easier to call these functions with Numpy indexing
routines, which work with signed integers. Also, saved multi-order sky maps
will now be read correctly by tools such as ``fv`` from HEASOFT, which do not
correctly handle unsigned integer columns.

- Add timestamps to the command line tools' default logging configuration in
order to start characterizing the latency of BAYESTAR's data handling stages.

- Increase precision of BAYESTAR's run time measurement for the FITS headers.

==================

- Add the ``ligo-skymap-plot-observability`` tool to plot observability windows
for many sites at once. Conceptually, this tool is a variation of
``ligo-skymap-plot-airmass`` in which the sky position is integrated out.

- The ``ligo-skymap-plot-airmass`` tool will now use the color map's full
dynamic range.

- Add ``order`` option to ``ligo.skymap.moc.rasterize`` and
``ligo.skymap.bayestar.rasterize`` and ``--nside`` option to
``ligo-skymap-flatten`` to support flattening multi-resolution HEALPix
datasets to specified resolutions.

- ``ligo-skymap-stats`` now ignores skymaps with no corresponding entries in
the inspinjfind database, instead of failing.

==================

- Add options to ``ligo-skymap-plot-airmass`` to specify site coordinates
explicitly rather than by a site nickname.