v1.18.0

• New get_epsilon_grid function for evaluating ε on user-specified grid with arbitrary resolution (#1522).

• Support for user-specified chunk layouts for manual control over load-balancing (#1528).

• MaterialGrid design_parameters is renamed to weights and U_SUM is renamed to U_MEAN (#1512).

• Performance improvement in chunk division (#1499).

• Various bugfixes (#1487, #1515, #1519, #1521, #1527), additional documentation, and tests.

v1.17.1

• Fix accidental breakage of the adjoint routines ([#1464]).

v1.17.0

• get_array_slice now does continuous interpolation as the slice position is moved (#1456).

• New contour option for contour-plotting in plot2D (#1437).

• Adjoint optimization of near2far transformations (#1417).

• get_array_metadata is now consistent between array slices and DFT slices (#1456), no longer leaks memory (#1447), and returns numpy arrays rather than tuples (#1458).

• Bugfixes in adjoint-optimization filters (#1427).

v1.16.1

• Bugfix in adjoint code (#1403).

v1.16.0

• Gaussian beam source feature (#1303 and #1310).

• New API for specifying planewave diffraction orders for eigenmode sources
  and coefficients (#1316).

• More accurate gradients in adjoint code (#1285).

• Simpler Python API for outputting ε or μ at a given frequency (#1374).

• --with-libctl-dir option of configure now accepts simply the installation prefix in addition to prefix/share/libctl (#1286).

• Less verbose mode-solver output from MPB (#1302, #1388), and new
  meep.verbosity option in Python (#1349).

• Bug fix for single-point DFT monitor (#1333).

v1.15.0

• Minimum-lengthscale filters for adjoint optimization (#1205).

• Python API documentation in docstrings (#1240).

• MaterialGrid material type in Python to interpolate an array of material
  values as the "material" of an object, especially for topology optimization (#1242).

• merge_subgroup_data Python function for coordinating parallel
  computations (#1192).

• Eigenmode sources now ensure that the source has the same
  frequency as the mode (#1218).

• Performance improvements to eigenmode sources (#1233, #1244, #1257).

v1.14.0

• New adjoint solver for density-based topology optimization, including
  filtering, automatic differentiation, and other frequencies (#1167).

• DFT functions now allow you to pass an arbitrary array of frequencies, instead
  of being limited to equally spaced frequencies (#1154 and #1156).

• Experimental shift-and-invert frequency-domain eigensolver (#1158).

• Renamed omega parameter to frequency at some places in the Python API,
  for consistency (#1171), and dft_fields object now takes fcen and df instead
  of freq_min and freq_max in Python.

• Support for SWIG 4.0 (#1159), and various other minor fixes.

v1.13.1

• Avoid writing to source directory in remaining tests (#1132).

v1.13.0

• Optional parameter omega for output-epsilon and similar functions,
  allowing the complex ε and μ at a given frequency to be outputted (#1112, following #919).

• near2far computation now supports cylindrical coordinates (#1090).

• Experimental support for slanted prisms (requires libctl 4.5)
  via sidewall_angle parameter to prism objects (#1129).

• New yee_grid=False optional argument to add_dft_fields; by passing True
  one can compute the fields on the original Yee grid (#1095).

• New function meep::make_output_directory() to make a temporary
  directory (in TMPDIR or similar) and meep::delete_directory(path)
  to perform recursive deletion (like rm -rf). These are now
  used in tests to avoid writing to the source directory (#1121, #1122 and #1126).

• Jupyter notebooks now show a graphical progress bar during simulations (#1078).

• kz-2d option in Scheme, mirroring Python kz_2d (#1062).

• Various bugfixes, documentation supplements, and other minor improvements.

v1.12.0

• Faster 2d simulations with nonzero kz via the kz_2d option (#1047).

• New Meep verbosity option superseding quiet and verbose flags (#994).

• Output now only shows ≤ 10 geometric objects by default (#1002).

• Performance improvements for split_chunks_evenly=False.

• Fixed memory leaks (#1041, #1042).