.. highlight:: yaml

.. _section-input_guide_sg:

|Structure gene|
=============================

This block stores |structure gene| definitions.
The |sg_key| block is a library storing a list of base designs of |structure genes| that will be used for the global structure.
Note that both ``structure`` and |sg_key| blocks share some common input entries.
These entries have mostly the same input syntax and meanings.
The basic method defining a |structure gene| is as follows:


#. Create a base design of the |structure genes|
#. Identify designable parameters
#. Assign default values to those parameters


The overall layout is shown in :numref:`Listing %s <lst-input_sg_layout>`.

..  code-block:: yaml
    :name: lst-input_sg_layout
    :caption: Layout of the |sg_key| input block

    cs:
      - name: ""
        parameter:
          ...
        design:
          ...
        model:
          ...
      - name: ""
        ...


Two key entries are the ``design``, which specifies the base design, and ``parameter``, which specifies the designable parameters.

..  note::

    For more information on the parameterization of beam structures and cross-sections, please check the Section :ref:`section-ivabs_parameterization`.









Parameter specifications (``parameter``)
-------------------------------------------

In this section, design parameters of a |sg_key| are given in a list of pairs of name and value.
The basic syntax is shown in :numref:`Listing %s <lst-input_sg_param_list>`.

..  code-block:: yaml
    :name: lst-input_sg_param_list
    :caption: Parameter list

    cs:
      - name: "cs1"
        parameter:
          param_3: value_3
          param_4: value_4
          ...

Parameter list can be used to specify a constant value for the whole structure.
These parameters can also be varied by an optimization method.
This is done by directly using the parameter name as the design variable name in the :ref:`section-input_guide_study` block.