=======
Outputs
=======

This section explains interpretation of the resulting output files generated by ZigZag. There are currently two predefined ``SaveStages``, which save the results to a ``.json`` file in different ways.

Saving a ``CostModelEvaluation`` object to a ``.json`` requires knowledge of what attributes of the object are relevant/irrelevant. This is handled by the ``complexHandler`` inside the ``SaveStage``.

The ``complexHandler`` handles the json representation that should be invoked for each object passed to it. In for example the ``SimpleSaveStage``, the ``__simplejsonrepr__`` method of the ``CostModelEvaluation`` object specifies how this should be converted to a json format.

SimpleSaveStage
===============

This stage only saves the energy and latency including data on- and off-loading. It relies on the ``__simplejsonrepr__`` method, which is defined in the ``CostModelEvaluation`` object as:

.. code:: python

    def __simplejsonrepr__(self):
        """
        Simple JSON representation used for saving this object to a simple json file.
        """
        return {
            "energy": self.energy_total,
            "latency": self.latency_total2
        }

Note that saving these two numbers in combination with the standard ``filename_pattern`` loses all information with respect to: which layer, which spatial mapping, which temporal mapping, etc. this ``CostModelEvaluation`` is concerning.

CompleteSaveStage
=================

This stage saves all relevant attributes of the ``CostModelEvaluation`` to a json file, using the following ``__jsonrepr__`` definition inside the ``CostModelEvaluation``:

.. code:: python

    def __jsonrepr__(self):
        """
        JSON representation used for saving this object to a json file.
        """
        return {
            "inputs": {
                "accelerator": self.accelerator,
                "node": self.node,
                "spatial_mapping": self.spatial_mapping,
                "temporal_mapping": self.temporal_mapping,
            },
            "outputs": {
                "memory": {
                    "utilization": self.mem_utili_shared,
                    "word_accesses": self.memory_word_access
                },
                "energy": {
                    "energy_total": self.energy_total, 
                    "operational_energy": self.MAC_energy,
                    "memory_energy": self.mem_energy,
                    "energy_breakdown_per_level": self.energy_breakdown,
                    "energy_breakdown_per_level_per_operand": self.energy_breakdown_further
                },
                "latency": {
                    "latency_without_onloading_without_offloading": self.latency_total0,
                    "latency_with_onloading_without_offloading": self.latency_total1,
                    "latency_with_onloading_with_offloading": self.latency_total2
                }
            }
        }

The ``self.accelerator`` attribute is an ``Accelerator`` object, which also includes a ``__jsonrepr__`` method to know how this should be converted to a json format.

Creating a custom SaveStage
===========================

The main goal of working with a hierarchy of stages is to make modification easy and straightforward. If you care only about a certain aspect of the results, you can create a custom ``SaveStage`` and modify its ``complexHandler``.

Please see :ref:`custom-stages-label`.