Abstract: A graphics processing system for operation with a data store, comprising: one or more processing units for processing tasks; a check unit operable to form a signature which is characteristic of an output from processing a task on a processing unit; and a fault detection unit operable to compare signatures formed at the check unit; wherein the graphics processing system is operable to process each task first and second times at the one or more processing units so as to, respectively, generate first and second processed outputs, the graphics processing system being configured to: write out the first processed output to the data store; read back the first processed output from the data store and form at the check unit a first signature which is characteristic of the first processed output as read back from the data store; form at the check unit a second signature which is characteristic of the second processed output; compare the first and second signatures at the fault detection unit; and raise a fault signal i

Abstract: A method of rendering, in a rendering space, a scene formed by primitives in a graphics processing system. A geometry processing phase includes the step of storing fragment shading rate data representing a first fragment shading rate value and associating data identifying a primitive with the fragment shading rate data. A rendering phase includes the steps of retrieving the stored fragment shading rate data and associated data identifying the primitive, obtaining an attachment specifying one or more attachment fragment shading rate values for the rendering space; processing the primitive to derive primitive fragments to be shaded; and for each primitive fragment, combining the first fragment shading rate value for the primitive from which the primitive fragment is derived with an attachment fragment shading rate value from the attachment to produce a resolved combined fragment shading rate value for the respective fragment.

Abstract: A method of operation of a texturing/shading unit in a GPU pipeline is used for efficient convolution operations. The method uses texture hardware to collectively fetch all the texels required to calculate properties for a group of output pixels without any duplication. The method then bypasses bilinear filter hardware in the texture hardware and passes the fetched and unfiltered texel data from the texture hardware unit to shader hardware in the texturing/shading unit. The shader hardware uses the fetched texel data to perform a plurality of convolution operations to calculate the properties of each of the output pixel.

Abstract: A method of performing anisotropic texture filtering includes generating one or more parameters describing an elliptical footprint in texture space; performing isotropic filtering at each of a plurality of sampling points along a major axis of the elliptical footprint, wherein a spacing between adjacent sampling points of the plurality of sampling points is proportional to ?{square root over (1???2)} units, wherein ? is a ratio of a major radius of an ellipse to be sampled and a minor radius of the ellipse to be sampled, wherein the ellipse to be sampled is based on the elliptical footprint; and combining results of the isotropic filtering at the plurality of sampling points with a Gaussian filter to generate at least a portion of a filter result.

Abstract: A single-instruction, multiple data processor performs object detection in an image by testing for a plurality of object features in a plurality of image regions, the processor comprising: a set of computation units operable to execute a plurality of classifier sequences in parallel, each classifier sequence comprising a plurality of classifier routines, and each classifier routine comprising identical instructions to the other classifier routines in each of the plurality of classifier sequences; wherein each computation unit is configured to independently maintain data identifying an image region and a feature under test on that computation unit, and each classifier routine is arranged to access the data, test the identified feature against the identified image region and update the data such that the computation units are operable to concurrently test different features against different image regions.

Abstract: A method and system for performing safety-critical rendering of a frame in a tile based graphics processing system. Geometry data for the frame is received, including data defining a plurality of primitives representing a plurality of objects in the frame. A definition of a region in the frame is received, the region being associated with one or more primitives among the plurality of primitives. Verification data is received that associates one or more primitives with the region in the frame. The frame is rendered using the geometry data and the rendering of the frame is controlled using the verification data, so that the rendering excludes, from the frame outside the region, the primitives identified by the verification data.

Abstract: A binary logic circuit for determining the ratio x/d where x is a variable integer input, the binary logic circuit comprising: a logarithmic tree of modulo units each configured to calculate x[a: b]mod d for respective block positions a and b in x where b>a with the numbering of block positions increasing from the most significant bit of x up to the least significant bit of x, the modulo units being arranged such that a subset of M?1 modulo units of the logarithmic tree provide x[0: m]mod d for all m?{1, M}, and, on the basis that any given modulo unit introduces a delay of 1: all of the modulo units are arranged in the logarithmic tree within a delay envelope of [log2 M]; and more than M?2u of the subset of modulo units are arranged at the maximal delay of [log2 M], where 2u is the power of 2 immediately smaller than M.

Abstract: A tile-based graphics system has a rendering space sub-divided into a plurality of tiles which are to be processed. Graphics data items, such as parameters or texels, are fetched into a cache for use in processing one of the tiles. Indicators are determined for the graphics data items, whereby the indicator for a graphics data item indicates the number of tiles with which that graphics data item is associated. The graphics data items are evicted from the cache in accordance with the indicators of the graphics data items. For example, the indicator for a graphics data item may be a count of the number of tiles with which that graphics data item is associated, whereby the graphics data item(s) with the lowest count(s) is (are) evicted from the cache.

Abstract: A method of processing primitives within a tiling unit of a graphics processing system comprises determining whether a primitive falls within a tile based on positions of samples within each pixel. If it is determined that the primitive does fall within a tile based on the positions of samples within pixels in a tile, an association between the tile and the primitive is stored to indicate that the primitive is present in the tile. For example, an identifier for the primitive may be added to a control stream for the tile to indicate that the primitive is present in the tile. Various different methods are described to make the determination and these may be used separately or in any combination.

Abstract: A SIMD microprocessor is configured to execute programs divided into discrete phases. A scheduler is provided for scheduling instructions. A plurality of resources are for executing instructions issued by the scheduler, wherein the scheduler is configured to schedule each phase of the program only after receiving an indication that execution of the preceding phase of the program has been completed. By splitting programs into multiple phases and providing a scheduler that is able to determine whether execution of a phase has been completed, each phase can be separately scheduled and the results of preceding phases can be used to inform the scheduling of subsequent phases. In one example, different numbers of threads and/or different numbers of data instances per thread may be processed for different phases of the same program.

Abstract: A method in a hardware implementation of a Convolutional Neural Network (CNN), includes receiving a first subset of data having at least a portion of weight data and at least a portion of input data for a CNN layer and performing, using at least one convolution engine, a convolution of the first subset of data to generate a first partial result; receiving a second subset of data comprising at least a portion of weight data and at least a portion of input data for the CNN layer and performing, using the at least one convolution engine, a convolution of the second subset of data to generate a second partial result; and combining the first partial result and the second partial result to generate at least a portion of convolved data for a layer of the CNN.

Abstract: Hardware monitors which can be used by a formal verification tool to exhaustively verify a hardware design for a memory unit. The hardware monitors include detection logic to monitor one or more control signals and/or data signals of an instantiation of the memory unit to detect symbolic writes and symbolic reads. In some examples a symbolic write is a write of symbolic data to a symbolic address; and in other examples a symbolic write is a write of any data to a symbolic address. A symbolic read is a read of the symbolic address. The hardware monitors also include assertion verification logic that verifies an assertion that read data corresponding to a symbolic reads matches write data associated with one or more symbolic writes preceding the read.

Abstract: Graphics processing systems may render multiple views of a scene (e.g. a sequence of frames) in a tile-based manner. Groups of views may be rendered together such that tiles from a group of views are rendered in an interspersed order such that at least one tile from each of the views in the group is rendered before any of the views of the scene in the group are fully rendered. In this way similar tiles from different views within a group may be rendered sequentially. If a particular rendered tile is similar to the next tile to be rendered then data stored in a cache for rendering the particular tile is likely to be useful for rendering the next tile. Therefore, when rendering the next tile less data needs to be fetched from the system memory which can significantly improve the efficiency of the graphics processing system.

Abstract: A converter module is described which handles memory requests issued by a cache (e.g. an on-chip cache), where these memory requests include memory addresses defined within a virtual memory space. The converter module receives these requests, issues each request with a transaction identifier and uses that identifier to track the status of the memory request. The converter module sends requests for address translation to a memory management unit and where there the translation is not available in the memory management unit receives further memory requests from the memory management unit. The memory requests are issued to a memory via a bus and the transaction identifier for a request is freed once the response has been received from the memory. When issuing memory requests onto the bus, memory requests received from the memory management unit may be prioritized over those received from the cache.

Abstract: A method of verifying processing logic of a graphics processing unit receives a test task including a predefined set of instructions for execution on the graphics processing unit, the predefined set of instructions being configured to perform a predetermined set of operations on the graphics processing unit when executed for predefined input data. In a test phase, the test task is processed by executing the predefined set of instructions for the predefined input data first and second times at the graphics processing unit so as to, respectively, generate first and second outputs. A fault signal is raised if the first and second outputs do not match.

Abstract: A method of processing an input task in a processing system involves duplicating the input task so as to form a first task and a second task; allocating memory including a first block of memory configured to store read-write data to be accessed during the processing of the first task; a second block of memory configured to store a copy of the read-write data to be accessed during the processing of the second task; and a third block of memory configured to store read-only data to be accessed during the processing of both the first task and the second task; and processing the first task and the second task at processing logic of the processing system so as to, respectively, generate first and second outputs.

Abstract: A method and apparatus are provided for allocating memory for geometry processing in a 3-D graphics rendering system comprising multiple cores. Geometry processing work is divided up into discrete work-packages, which form an ordered sequence. Cores are assigned different work-packages to process, and make memory allocation requests to enable them to store the results of the processing. Memory allocation requests relating to the current earliest uncompleted work-package in the sequence are treated differently to other requests, and may be prioritised.

Abstract: A method of controlling the order in which primitives, generated during tessellation, are output by the tessellation unit involves sub-dividing a patch, selecting one of the two sub-patches which are formed by the sub-division and tessellating that sub-patch until no further sub-division is possible before tessellating the other (non-selected) sub-patch. The method is recursively applied at each level of sub-division. Patches are output as primitives at the point in the method where they do not require any further sub-division. The selection of a sub-patch is made based on the values of one or more flags and any suitable tessellation method may be used to determine whether to sub-divide a patch. Methods of controlling the order in which vertices are output by the tessellation unit are also described and these may be used in combination with, or independently of, the method of controlling the primitive order.

Abstract: A graphics processing system performs hidden surface removal and texturing/shading on fragments of primitives. The system includes a primary depth buffer (PDB) for storing depth values of resolved fragments, and a secondary depth buffer (SDB) for storing depth values of unresolved fragments. Incoming fragments are depth tested against depth values from either the PDB or the SDB. When a fragment passes a depth test, its depth value is stored in the PDB if it is a resolved fragment (e.g. if it is opaque or translucent), and its depth value is stored in the SDB if it is an unresolved fragment (e.g. if it is a punch through fragment). This provides more opportunities for subsequent opaque objects to overwrite punch through fragments which passed a depth test, thereby reducing unnecessary processing and time which may be spent on fragments which ultimately will not contribute to the final rendered image.

Abstract: Methods and coarse depth test logic perform coarse depth testing in a graphics processing system in which a rendering space is divided into a plurality of tiles. A depth range for a tile identifies a depth range based on primitives previously processed. A determination is made based on the depth range for the tile as to whether all or a portion of a primitive is hidden in the tile. If at least a portion of the primitive is not hidden in the tile, a determination is made as to whether the primitive or a primitive fragment thereof has better depth than the primitives previously processed for the tile. If so, the primitive or the primitive fragment is identified as not requiring a read of a depth buffer to perform full resolution depth testing, such that a determination that at least a portion of the primitive is hidden in the tile causes full resolution depth testing not to be performed on at least that portion of the primitive.