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Add paramter emphasis and setting
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Joao-Dionisio committed Oct 2, 2024
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2 changes: 1 addition & 1 deletion docs/tutorials/constypes.rst
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Expand Up @@ -80,7 +80,7 @@ coefficient values, and the constraint handler that created the Row.
Constraint Information
========================
======================

The Constraint object can be queried like any other object. Some of the information a Constraint
object contains is the name of the constraint handler responsible for the constraint,
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84 changes: 83 additions & 1 deletion docs/tutorials/model.rst
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Expand Up @@ -109,6 +109,88 @@ all the parameter values that you wish to set, then one can use the command:
scip.readParams(path_to_file)
Automatically set plugin parameters
===================================
We can influence the behavior of some of SCIP's plugins using ``SCIP_PARAMSETTING``. This can be applied
to the heuristics, to the presolvers, and to the separators (respectively with ``setHeuristics``,
``setPresolve``, and ``setSeparating``).
.. code-block:: python
from pyscipopt import Model, SCIP_PARAMSETTING
scip = Model()
scip.setHeuristics(SCIP_PARAMSETTING.AGGRESSIVE)
There are four parameter settings:
.. list-table:: A list of the different options and the result
:widths: 25 25
:align: center
:header-rows: 1
* - Option
- Result
* - ``DEFAULT``
- set to the default values of all the plugin's parameters
* - ``FAST``
- the time spend for the plugin is decreased
* - ``AGGRESSIVE``
- such that the plugin is called more aggressively
* - ``OFF``
- turn off the plugin
.. note:: This is important to get dual information, as it's necessary to disable presolving and heuristics.
For more information, see the tutorial on getting :doc:`constraint information.</tutorials/constypes/>`
Set solver emphasis
===================
One can also instruct SCIP to focus on different aspects of the search process. To do this, import
``SCIP_PARAMEMPHASIS`` from ``pyscipopt`` and set the appropriate value. For example,
if the goal is just to find a feasible solution, then we can do the following:
.. code-block:: python
from pyscipopt import Model, SCIP_PARAMEMPHASIS
scip = Model()
scip.setEmphasis(SCIP_PARAMEMPHASIS.FEASIBILITY)
You can find below a list of the available options, alongside their meaning.
.. list-table:: Parameter emphasis summary
:widths: 25 25
:align: center
:header-rows: 1
* - Setting
- Meaning
* - ``PARAMEMPHASIS.DEFAULT``
- to use default values
* - ``PARAMEMPHASIS.COUNTER``
- to get feasible and "fast" counting process
* - ``PARAMEMPHASIS.CPSOLVER``
- to get CP like search (e.g. no LP relaxation)
* - ``PARAMEMPHASIS.EASYCIP``
- to solve easy problems fast
* - ``PARAMEMPHASIS.FEASIBILITY``
- to detect feasibility fast
* - ``PARAMEMPHASIS.HARDLP``
- to be capable to handle hard LPs
* - ``PARAMEMPHASIS.OPTIMALITY``
- to prove optimality fast
* - ``PARAMEMPHASIS.PHASEFEAS``
- to find feasible solutions during a 3 phase solution process
* - ``PARAMEMPHASIS.PHASEIMPROVE``
- to find improved solutions during a 3 phase solution process
* - ``PARAMEMPHASIS.PHASEPROOF``
- to proof optimality during a 3 phase solution process
* - ``PARAMEMPHASIS.NUMERICS``
- to solve problems which cause numerical issues
Copy a SCIP Model
==================
Expand All @@ -122,7 +204,7 @@ This model is completely independent from the source model. The data has been du
That is, calling ``scip.optimize()`` at this point will have no effect on ``scip_alternate_model``.
.. note:: After optimizing users often struggle with reoptimization. To make changes to an
already optimized model, one must first fo the following:
already optimized model, one must first do the following:
.. code-block:: python
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