Vela Debug Database

The purpose of the debug database is to track operator transformations during the optimisation process of Vela. This is later correlated with the trace output of the model, externally, to determine the runtime of the original layer operators. Standalone, the debug database can be used in order to give a brief overview of how the operators in the network change throughout the optimisation process. This document gives an overview of the structure of the database and its outputs, to help parsing of the generated data in a debug procedure.


While processing, Vela maintains information about operator substitutions and command generation in its internal Debug Database. The database tracks the data transformations through the following states:

  • Creation of Source operators - these operators are created from the source representation, in this case the original TFLite file
  • Creation of Optimised operators - these are the operators that result from optimising the source operators. They may be the source operators repeated, or substitute operators inserted by the optimiser
  • Creation of Queue commands - these are the register command sequences generated by the code generator from the optimised operators

Vela's processing steps add data to internal debug tables; one table for each of the above states. When vela has completed processing it can write out the internal debug tables through the command line option --enable-debug-db.

File Format

The internal debug tables are formatted as columnar CSV. Each row represents an operator or stream command; keyed on a numeric value that uniquely identifies that operator or command. These tables are further packaged into an XML container file, along with metadata, for easier transport and handling.

Debug node

The top-level debug node wraps the entire file and contains information about the source and optimised file paths.

<debug optimised="output_from_vela.tflite" source="input.tflite">

Table nodes

The top-level debug node contains one or more table nodes. Each table node is named, and the table data is represented as CSV formatted text stored in a CDATA payload tag. The first row of the table contains column headers.

<table name="source"><![CDATA[ "column0", "column1", "column2", ... ]]></table>

There currently are 4 named tables.

  • source - Table of TFLite operators from the source file.
  • optimised - Table of optimised operators generated by vela
  • queue - Table of command queue offsets
  • cmdstream - Table describing properties of one or more command streams

The tables reference each other through the following connections: the queue table is linked to the optimised table through the optimised_id and the command stream table through the cmdstream_id. The optimised table is in turn linked to the source table through the source_id.


Note that the source, cmdstream and optimised tables are not ordered in any particular way. The insertion order of entries in the source and optimised tables is due to Vela's internal operation and does not represent a graph structure. The only ordered table is the queue; which is ordered by its queue offset. This table describes the execution order of the hardware commands, and they can be mapped back to the optimised and source operators in order to determine their execution order.