Method of and apparatus for generating a signature representative of the content of an array of data

A method of providing a data array for use in a data processing system, the data processing system comprising a graphics processing system, the array of data comprising a render target output generated by the graphics processing system, the data array being formed of one or more regions, each region of the array of data comprising plural data positions, and each data position having an associated data value or values and having an associated position in the array of data, the method comprising circuitry performing the following:

• generating a first rendered data value or values for a data position of the region of the data array;
• writing the first data rendered value or values for the data position of the region of the data array to storage that stores the region of the data array as it is being generated;
• generating a first signature representative of the content of the region of the data array in parallel with the first rendered data value or values for the data position of the region of the data array being written to the storage, including using the associated position in the array of data of the data position when generating the first signature representative of the content of the region of the data array;
• storing the first signature to external memory;
• repeatedly generating further rendered data values for the region of the data array in an unpredictable data position order, wherein the further rendered data values may be for the same data position of the region of the data array as the previously generated first data value;
• for each further rendered data value, identifying a data position of the region of the data array for said further rendered data value, and determining whether the identified data position of the region of the data array for said further rendered data value is the same as the data position of the previously generated first rendered data value or values;
• and
• when it is determined that the identified data position of the region of the data array for the further data value or values is the same as the data position of the previously generated first rendered data value or values;
• writing the further rendered data value or values for the data position of the region of the data array to storage that stores the region of the data array as it is being generated to replace the previously stored first data value or values for the data position of the region of the data array;
• generating an updated signature representative of the content of the region of the data array in parallel with the further rendered data value or values for the data position of the region of the data array being written to the storage, wherein the step of generating the updated signature representative of the content of the region of the data array uses:
• the further rendered data value or values for the data position of the region of the data array, and the first rendered data value or values for the data position which had previously been generated and stored for the data position, and the associated position in the array of data of the data position, to generate the updated signature representative of the content of the region of the data array;
• and
• comparing the new signature representative of the current region of the data array with a signature of a preceding region generated previously and stored in an external memory to determine if the current region is similar to the preceding region.

An apparatus for generating a signature representative of the content of a region of an array of data in a data processing system, the data processing system comprising a graphics processing system, the array of data comprising a render target output generated by the graphics processing system, the region of the array of data comprising plural data positions, each data position having an associated data value or values and having an associated position in the array of data, the apparatus comprising:

• data value generating circuitry capable of repeatedly generating rendered data values for data positions of a region of a data array to be generated comprising a render target output, the data value generating circuitry generating rendered data values for data positions of the region of the data array in an unpredictable data position order;
• storage capable of storing the rendered data values for a region of a data array comprising a render target output as the region of the data array is being generated;
• write circuitry capable of writing the generated rendered data values for data positions of a region of a data array comprising a render target output to the storage that stores the region of the data array as it is being generated;
• and
• signature generation circuitry capable of generating a signature representative of the content of a region of a data array comprising a render target output that is being generated in parallel with the writing of the rendered data value or values for the region of the data array to the storage;
• wherein the write circuitry is operable to, when a new rendered data value or values generated by the data value generating circuitry according to an unpredictable data position order:
• identify a data position of the region of the data array for said new rendered data value;
• determine whether the identified data position of the region of the data array for said new rendered data value is the same as the data position of a previously generated first rendered data value or values;
• and
• when it is determined that the identified data position of the region of the data array for the new rendered data value or values is the same as the data position of the region of the data array for the first rendered data value or values which has previously been generated and written to the storage, write the new rendered data value or values for the data position of the region of the data array to the storage to replace the previously stored first rendered data value or values for the data position of the region of the data array;
• and
• wherein the signature generating circuitry is operable to, when the write circuitry has written a new rendered data value or values for a data position of the region of the data array to the storage to replace a previously stored first rendered data value or values for the data position of the region of the data array, generate an updated signature representative of the content of the region of the data array in parallel with the writing of the new rendered data value or values to the storage using:
• the replaced first rendered data value or values, and the new rendered data value or values, and the associated position in the array of data of the data position, to generate the updated signature representative of the content of the region of the data array.

A system for providing a data array for use in a data processing system the data processing system comprising a graphics processing system, the array of data comprising a render target output generated by the graphics processing system, the data array being formed of one or more regions, each region of the array of data comprising plural data positions, and each data position having an associated data value or values and having an associated position in the array of data, the system comprising:

• an apparatus for generating a signature representative of the content of a region of an array of data for a current region of the data array, the apparatus comprising;
• data value generating circuitry capable of repeatedly generating rendered data values for data positions of a region of a data array to be generated comprising a render target output, the data value generating circuitry generating rendered data values for data positions of the region of the data array in an unpredictable data position order;
• storage capable of storing the rendered data values for a region of a data array comprising a render target output as the region of the data array is being generated;
• write circuitry capable of writing the generated rendered data values for data positions of a region of a data array comprising a render target output to the storage that stores the region of the data array as it is being generated;
• signature generation circuitry capable of generating a signature representative of the content of a region of a data array comprising a render target output that is being generated in parallel with the writing of the rendered data value or values for the region of the data array to the storage;
• wherein the write circuitry is operable to, when a new rendered data value or values generated by the data value generating circuitry according to an unpredictable data position order:
• identify a data position of the region of the data array for said new rendered data value;
• determine whether the identified data position of the region of the data array for said new rendered data value is the same as the data position of a previously generated first rendered data value or values;
• and
• when it is determined that the identified data position of the region of the data array for the new rendered data value or values is the same as the data position of the region of the data array for the first rendered data value or values which has previously been generated and written to the storage, write the new rendered data value or values for the data position of the region of the data array to the storage to replace the previously stored first rendered data value or values for the data position of the region of the data array;
• and wherein the signature generating circuitry is operable to, when the write circuitry has written a new rendered data value or values for a data position of the region of the data array to the storage to replace a previously stored first rendered data value or values for the data position of the region of the data array, generate an updated signature representative of the content of the region of the data array in parallel with the writing of the new rendered data value or values to the storage using:
• the replaced first rendered data value or values, and the new rendered data value or values, and the associated position in the array of data of the data position, to generate the updated signature representative of the content of the region of the data array;
• the system further comprising:
• a memory external to the apparatus for generating a signature representative of the content of a region of an array of data;
• write circuitry capable of writing to the external memory a signature representative of the content of a current region of a data array;
• and
• comparison circuitry capable of comparing the signature of a current region with a signature of a preceding region generated previously and stored in the external memory to determine if the current region is similar to the preceding region.

A non-transitory computer readable storage medium storing computer software code which when executing on a processor performs a method of generating a signature representative of the content of a region of an array of data in a data processing system, the data processing system comprising a graphics processing system, the array of data comprising a render target output generated by the graphics processing system, wherein the region of the array of data comprises plural data positions, each data position having an associated data value or values and having an associated position in the array of data, the method comprising:

• generating a first rendered data value or values for a data position of the region of the data array;
• writing the first rendered data value or values for the data position of the region of the data array to storage that stores the region of the data array as it is being generated;
• generating a first signature representative of the content of the region of the data array in parallel with the first rendered data value or values for the data position of the region of the data array being written to the storage, including using the associated position in the array of data of the data position when generating the first signature representative of the content of the region of the data array;
• repeatedly generating further rendered data values for the region of the data array in an unpredictable data position order, wherein the further rendered data values may be for the same data position of the region of the data array as the previously generated first data value;
• for each further rendered data value, identifying a data position of the region of the data array for said further rendered data value, and determining whether the identified data position of the region of the data array for said further rendered data value is the same as the data position of the previously generated first rendered data value or values;
• and
• when it is determined that the identified data position of the region of the data array for the further rendered data value or values is the same as the data position of the previously generated first rendered data value or values:
• writing the further rendered data value or values for the data position of the region of the data array to the storage that stores the region of the data array as it is being generated to replace the previously stored first data value or values for the data position of the region of the data array;
• and
• generating an updated signature representative of the content of the region of the data array in parallel with the further rendered data value or values for the data position of the region of the data array being written to the storage, wherein the step of generating the updated signature representative of the content of the region of the data array uses:
• the further rendered data value or values for the data position of the region of the data array, and the first rendered data value or values for the data position which had previously been generated and stored for the data position, and the associated position in the array of data of the data position, to generate the updated signature representative of the content of the region of the data array.