=======================
Exchangeable components
=======================

* :ref:`dev_guide_input`
* :ref:`dev_guide_qa`
* **Estimation component**
* :ref:`dev_guide_search`
* :ref:`dev_guide_output`


.. image:: ../images/components/component_overview_estimation.png
	:alt: Estimation component overview


.. _dev_guide_estimation:

Estimation component
====================

	.. note:: The Estimation component is not customizable yet.

	The *Estimation* component is used by the framework to generate statistics of the circuits generated during the approximation process. Statistics of interest are, for example, *area*, *delay*, *power*, *energy*, and *error*. These statistics can either be directly used or incorporated into a heuristic to compare circuits with each other. This information can then guide the search to improve the target metric. CIRCA currently invokes ABC's *if* command to synthesize a circuit and to obtain estimations about *area*, *delay*, and *power dissipation due to switching*.

Functions
=========

.. .. todo:: Add links to function documentations

``estimateCircuitStats(nodes: List<Node>): None``
-------------------------------------------------

	This method implements the main functionality of the *Estimation* stage. It is called each time the approximation stage yields another set of approximated circuits. As for all stages, the circuits are represented by their ``Node``\ s, hence the parameter of the method is a list of ``Node`` instances.

	Every ``Node`` has a parameter called ``stats`` which contains a dictionary. Initially, this dictionary is empty, and it is this method's task to fill in useful statistics in the form of key-value entries like ``"statName": statValue`` where ``statName`` is one of the supported metrics and ``statValue`` is its value of type ``float``, or ``None`` if no value for this metric was found.

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:ref:`Back to the Developer Guide <dev_guide_exc_comps>`