The Loco main classΒΆ

The main Loco class can be imported from accinv.loco. Details for its usage are available in the API documentation. The following aspects are worth pointing out.

The most general way for specifying fit parameters is via parameters. The argument should be a list of parameter groups. These are available from the parameters module. However, there are a few shorthand arguments for specifying quadrupole, multipole and gain error parameters:

  • quadrupoles: expects the names of thick quadrupoles as specified in the model; this a shorthand for Quadrupoles.

  • multipoles: expects the name of thin multipoles as specified in the model; this a shorthand for Multipoles.

  • fit_gain_errors: expects a true or false value; if true, then it will automatically add those BPM/steerer gain errors which are not already present in parameters.

With customize_residuals and customize_jacobian, the user can supply two functions which allow to modify the computed residuals and Jacobian before they are passed to the optimizer.

The method allows to specify the maximum number of Jacobian evaluations via maxiter. Typically, it is a good idea to limit these. Otherwise, the convergence will be determined by the underlying optimizer.