13.10 Highlights of What’s New in Version 2021.1

Here is a summary of what’s changed since release 2020.5. Historical change logs are collected in Section 13.

13.10.1 Bug Fixes for Elements

• The EDRIFT element was being modeled as a regular DRIFT element when the concat_order parameter of run_setup was set to a non-zero value. This was reported by M. Venturini (LBNL).
• The STICKY parameter on the APCONTOUR element was ignored and always set to 1.

13.10.2 Bug Fixes for Commands

• A bug was fixed for the touschek_scatter command that resulted in a crash when there was a RECIRC element in the beamline. This was reported by M. Jebramicik (DESY). A. Xiao (ANL) helped uncover the cause.
• The ramp_elements and modulate_elements commands now work correctly in conjunction with load_parameters with change_defined_values=0.
• The final file, which is requested from run_setup, now contains additional parameters giving the minimum and maximum values of the particle coordinates at the end of the system; e.g., xpMaximum gives the maximum x coordinate. These quantities, like (almost) all quantities in the final file, are available for use in optimization_term expressions.

13.10.3 New and Modified Elements

• Several elements have a new parameter, N_SLICES, that replaces the inconsistently-used and misleadingly-named N_KICKS parameter. The N_KICKS parameter is still available for use, but is deprecated.
  • CCBEND, CSBEND, CSRCSBEND, FMULT, MULT: The N_KICKS parameter was poorly named. It actually gave the desired number of full integrator steps, or “slices.”
  • KQUAD, KSEXT, KQUSE: The N_KICKS parameter was actually the number of total integrator substeps. E.g., for the fourth-order integrator, dividing N_KICKS by 4 gave the number of slices.
• CSBEND, KQUAD, KSEXT, and KOCT have a parameter MALIGN_METHOD that permits invoking new misalignment methods based on work of M. Venturini [58]. Gregg Penn (LBNL) helped verify the new methods. Based on the value of this parameter, misalignment calculations are changed as follows:
  • MALIGN_METHOD=0: use the existing method. The new YAW and PITCH (or EYAW and EPITCH for CSBEND elements) parameters are ignored.
  • MALIGN_METHOD=1: use M. Venturini’s method, with misalignment parameters understood to be relative to the magnet entrance. The new YAW and PITCH (or EYAW and EPITCH for CSBEND elements) parameters become active. This is presently incompatible with the moments_output command.
  • MALIGN_METHOD=2: use M. Venturini’s method, with misalignment parameters understood to be relative to the magnet center. The new YAW and PITCH (or EYAW and EPITCH for CSBEND elements) parameters become active. This is presently incompatible with the moments_output command.
• The HMON, VMON, and MONI elements can be used to store turn-by-turn BPM readings by setting the STORE_TURN_BY_TURN parameter to 1. This can be used, for example, to create position-based triggers using modulate_elements.
• The GKICKMAP element was added, which provides a generalized kickmap that is not specific to undulators or wigglers (unlike UKICKMAP).
• The SCATTER element now supports uniform distributions in addition to the default gaussian distribution using the new DISTRIBUTION parameter.
• The CSBEND matrix no longer requires use of the relatively slow tracking-based matrix option when the steering parameters are used. The element also supports the XSTEERING and YSTEERING parameters to allow individual control of whether the element is used for steering.
• The individual-element steering parameters for KSEXT elements are no longer ignored.

13.10.4 New and Modified Commands

• The parameters output of the run_setup command now includes string quantities in the ParameterValueString column. Numerical quantities are stored in the ParameterValue column, as before.
• The run_setup command has a new parameter suppress_parameter_defaults. If set to a nonzero value, the data stored in the parameters output file will not contain data that match the default values. This can result in much smaller files and faster loading, with the downside that future changes to the defaults would impact the ability to reproduce a run using a saved parameter file.
• The load_parameters command now makes consistent use of the ParameterValueString column in any input files. If the ParameterValue column is present, it is used for numerical quantities, while the ParameterValueString column is used for string quantities only. If only ParameterValueString is present, elegant will attempt to scan the string values as needed for numerical values; this is not the preferred approach as it will degrade performance.
• The losses output of the run_setup command now provides the global coordinate angle in the horizontal plane when losses_include_global_coordinates=1. One can also now control the range of s coordinates for recorded particles using the losses_s_limit array.
• The correct_tunes and chromaticity commands now accept lists giving lower and upper strength limits for each family. In addition, the strength_log files are now compatible with load_parameters.
• The closed_orbit and correct commands now have a control that allows accepting a closed orbit results that exceeds the accuracy target, rather than considering this an error. This will allow correction or other computations to proceed in spite of poor convergence of the closed orbit.

13.10.5 Changes Specific to the MPI Parallel Version

• A problem was fixed with the particle-swarm optimizer that caused it to abort or return invalid results when a function evaluation yielded an invalid result. This was in response to issues raised by forum user marlibgin.

13.10.6 Changes to Related Programs and Files

The elegant distribution includes many programs and scripts that perform computations with elegant output data, provide interfaces with other programs, or prepare data for use with elegant. These are listed in Section 8.

Changes to these tools in this release include

• The program computeRBGGE, which allows computation of a generalized gradient expansion[50] for use with BGGEXP based on field data on a rectangular boundary [57], was improved to support automatic tuning of the number of gradients and multipoles. In addition, output of the implied field map is supported.
• The program computeCBGGE was added, which allows computation of a generalized gradient expansion based on field data on a circular-cylinder boundary [50]. It replaces the script computeGeneralizedGradients, providing better performance and features.
• The script generateBunchTrain was added. It allows generating particle input files for a fairly arbitrary multi-train bunch pattern.