Changelog

3.1.0 (unreleased)

Build system

• Added CMake option kep3_BUILD_CPP_LIBRARY (default ON). When set to OFF, the C++ library is not built from source and CMake will instead locate an existing installation via find_package. A descriptive FATAL_ERROR is emitted if the library cannot be found. This makes it possible to build only the Python bindings, tests, or benchmarks against an already-installed kep3.

Bug fixes

• Fixed pickling of TOPS gym classes. The lambdas passed as state2cart and equivalent callbacks to the internal UDP prevented serialization. They were replaced with functools.partial() wrapping small module-level helper functions (_cart_scale, _mee_to_cart, _cfunc_call), which are picklable by name.

• Fixed pickling of zoh. The C++ class is bound as _zoh_cpp in pykep.core, so pickle looked for pykep.leg._zoh_cpp when reconstructing objects. The alias was missing from pykep/leg/__init__.py (only _zoh was defined). Added _zoh_cpp = _core._zoh_cpp to make the lookup succeed, consistent with the existing _sims_flanagan and _sims_flanagan_alpha aliases.

• Fixed several bugs in pl2pl_N_impulses: a crash when phase_free=False and t0_bounds=None (t0 was assigned instead of t0_bounds); a dead/unreachable N_max < 2 guard; plot_primer_vector using MU_SUN instead of self._common_mu; alpha lower bounds of 0.0 in phase-free mode (now 1e-3, consistent with the non-phase-free path, to avoid log(0) in alpha2direct). The pretty method was also corrected to print times-of-flight in days (the internal decode stores durations in seconds, and the conversion was missing).

3.0.0 (23-05-2026)

pykep 3 is a complete reimagination of the library: a new C++23 core, a clean pybind11 Python interface, type-erased user-defined abstractions (udpla, udp, uda), native integration with pagmo and heyoka, and an expanded set of low-thrust transcriptions and benchmark problems.