1.3.3 (August 13, 2018)

  • fix for broken table layout in print_param() and print_matrix()
  • fix for missing error report when error is raised in user function
  • fix of printout when ipython is used as a shell
  • fix of slow convergence when analytical gradient is provided
  • improved user guide with more detail information and improved structure

1.3.2 (August 5, 2018)

  • allow fixing parameter by setting limits (x, x) with some value x
  • better defaults for maxcall arguments of hesse() and minos()
  • nicer output for print_matrix()
  • bug-fix: covariance matrix reported by iminuit was broken when some parameters were fixed
  • bug-fix: segfault when something in PythonCaller raised an exception

1.3.1 (July 10, 2018)

  • fixed failing tests when only you installed iminuit with pip and don’t have Cython installed

1.3 (July 5, 2018)

  • iminuit 1.3 is a big release, there are many improvements. All users are encouraged to update.
  • Python 2.7 as well as Python 3.5 or later are supported, on Linux, MacOS and Windows.
  • Source packages are available for PyPI/pip and we maintain binary package for conda (see Installation).
  • The bundled Minuit C++ library has been updated to the latest version (takend from ROOT 6.12.06).
  • The documentation has been mostly re-written. To learn about iminuit and all the new features, read the Tutorials.
  • Numpy is now a core dependency, required to compile iminuit.
  • For Numpy users, a second callback function interface and a Minuit.from_array_func constructor was added, where the parameters are passed as an array.
  • Results are now also available as Numpy arrays, e.g. np_values, np_errors and np_covariance.
  • A wrapper function iminuit.minimize for the MIGRAD optimiser was added, that has the same arguments and return value format as scipy.optimize.minimize.
  • Support for analytical gradients has been added, users can pass a grad callback function. This works, but for unknown reasons doesn’t lead to performance improvements yet. If you can help debug or fix this issue, please comment here.
  • Several issues have been fixed. A complete list of issues and pull requests that went into the 1.3 release is here.


  • For iminuit releases before v1.3, we did not fill a change log.
  • To summarise: the first iminuit release was v1.0 in Dec 2012. In 2013 there were several releases, and in Jan 2014 the v1.1.1 release was made. After that development was mostly inactive, except for the v1.2 release in Nov 2015.
  • The release history is available here:
  • The git history and pull requests are here: