Methods of and apparatus for using tree representations for representing arrays of data elements for encoding and decoding data in data processing systems

A method of generating an encoded version of an array of data elements for storage in a data processing system, the method comprising:

• generating at least one tree representation for representing the array of data elements, the data values for the nodes of the tree being set such that data values for the data elements of the data array that the tree represents can be derived from the data values for the nodes of the tree;
• generating data representing the node values of the at least one tree representing the data array;
• generating at least one further tree representation in which the node values for the at least one further tree indicate the number of bits used to indicate respective node values in the data generated to represent the node values of the at least one tree representing the data array;
• generating data representing the at least one further tree indicating the number of bits used to indicate the respective node values in the data generated to represent the node values of the at least one tree representing the data array;
• and
• storing the generated data representing the node values of the at least one tree representing the data array and the generated data representing the at least one further tree indicating the number of bits used to indicate the respective node values in the data generated to represent the node values of the at least one tree representing the data array, as an encoded version of the array of data elements.

A method of determining the value of a data element of a data array for use in a data processing system, the method comprising:

• using data representing a tree indicating the number of bits used to indicate respective node values in a set of stored data that represents the node values of a tree representing some or all of the data elements of the data array, to determine the number of bits used to indicate one or more node values in the set of stored data that represents the node values of the tree representing some or all of the data elements of the data array;
• using the determined number of bits to identify the stored data representing the data values of a node or nodes of the tree representing some or all the data elements of the data array;
• using the identified stored data representing the data values of a node or nodes of the tree representing some or all the data elements of the data array to determine the data values of a node or nodes of the tree representing some or all the data elements of the data array;
• and
• using the determined node values to determine the value to be used for a data element of the data array.

An apparatus for generating an encoded version of an array of data elements for storage in a data processing system, the apparatus comprising:

• processing circuitry that generates at least one tree representation for representing the array of data elements, the data values for the nodes of the tree being set such that data values for the data elements of the data array that the tree represents can be derived from the data values for the nodes of the tree, processing circuitry generates data representing the node values of the at least one tree representing the data array, processing circuitry generates at least one further tree representation in which the node values for the at least one further tree indicate the number of bits used to indicate respective node values in the data generated to represent the node values of the at least one tree representing the data array, processing circuitry generates data representing the at least one further tree indicating the number of bits used to indicate the respective node values in the data generated to represent the node values of the at least one tree representing the data array, and processing circuitry stores the generated data representing the node values of the at least one tree representing the data array and the generated data representing the at least one further tree indicating the number of bits used to indicate the respective node values in the data generated to represent the node values of the at least one tree representing the data array, as an encoded version of the array of data elements.

A non-transitory computer readable storage medium storing computer software code which when executing on a processor performs a method of generating an encoded version of an array of data elements for storage in a data processing system, the method comprising:

• generating at least one tree representation for representing the array of data elements, the data values for the nodes of the tree being set such that data values for the data elements of the data array that the tree represents can be derived from the data values for the nodes of the tree;
• generating data representing the node values of the at least one tree representing the data array;
• generating at least one further tree representation in which the node values for the at least one further tree indicate the number of bits used to indicate respective node values in the data generated to represent the node values of the at least one tree representing the data array;
• generating data representing the at least one further tree indicating the number of bits used to indicate the respective node values in the data generated to represent the node values of the at least one tree representing the data array;
• and
• storing the generated data representing the node values of the at least one tree representing the data array and the generated data representing the at least one further tree indicating the number of bits used to indicate the respective node values in the data generated to represent the node values of the at least one tree representing the data array, as an encoded version of the array of data elements.