40 results about "Bounds checking" patented technology

Incremental single and multiprocess checkpointing and restoration is described, which is transparent in that the application program need not be modified, re-compiled, or re-linked to gain the benefits of the invention. The processes subject to checkpointing can be either single or multi-threaded. The method includes incremental page-boundary checkpointing, as well as storage checkpointing of data files associated with applications to ensure correct restoration without the need to restore files for other application programs. Incremental and full checkpoints are asynchronously merged to ensure proper operation while reducing checkpointing delay. By way of example a user-level programming library is described for loading into the address space of the application in conjunction with a loadable kernel module (LKM) or device driver used to capture and restore process state on behalf of the application. These techniques are particularly well suited for use with high-availability (HA) protection programming.

This invention relates generally to a system for processing database queries, and more particularly to a method for generating high level language or machine code to implement query execution plans. The present invention provides a method for generating executable machine code for query execution plans, that is adaptive to dynamic runtime conditions, that is compiled just in time for execution and most importantly, that avoids the bounds checking, pointer indirection, materialization and other similar kinds of overhead that are typical in interpretive runtime execution engines.

A method and several variants for optimizing the detection of out of bounds array references in computer programs are described, while preserving the semantics of the computer program. Depending on the variant implemented, the program is divided at run-time or compile-time into two or more regions. The regions are differentiated by the number of checks that need to be performed at run-time on the array accesses within the region. In particular, some regions of the program will not need any array bounds checks performed at run-time, which will increase the speed at which the computer program executes. As well, the state of program variables at the time any out of bounds access is detected is the same as the state of the program variables would have been had the transformation not been performed. Moreover, the regions not needing any checks at run-time will be known at compile-time, enabling further compiler optimizations on the region. The variants of the method are distinguished by the number of regions created, the number of checks needed at run-time, and the size of the program that results from the optimization.

An error handling operation for checking of an array access in program code is modified during compilation thereof. A sequentially arranged null checking operation and array bounds checking operation for the array access are located. The array bounds checking operation has a corresponding error handling operation operable for setting an array bounds error. The located sequentially arranged null checking operation is removed. The corresponding error handling operation for the located sequentially arranged array bounds checking operation is modified to perform the removed null checking operation during execution of the program code.

The invention discloses a water body modeling method for a shallow water equation model with optimized parameters. According to the method, first, a three-dimensional dynamic coordinate system is constructed, and the shallow water equation model with optimized parameters is derived; when the model is solved, a reverse path tracking method and a method of characteristics are combined to solve an advective item in an equation, a vector projection method and a Fourier transformation method are combined to solve the effect of external acting force on a water body, and therefore a velocity field and a height field are updated; next, boundary check is performed, a boundary truncation method is adopted to process mesh points beyond a boundary; and last, the height field is drawn, and a next time period is processed cyclically. Compared with a traditional shallow water equation, when the contact surface between the water body and a solid is excessively steep, a water body model can be constructed more vividly and accurately, and the velocity of average 24.9 frame/second can be reached in the water body modeling simulation process; compared with a traditional method, the velocity is increased by 29.016%, and real-time simulation can be realized basically.

Some embodiments of the present invention provide techniques and systems for optimizing bounds-checking During operation, the system can receive one or more instructions which when executed evaluate a first expression whose value is required to be between a lower bound expression's value and an upper bound expression's value, such that at least one of the following three values is not determinable before execution: the first expression's value, the lower bound expression's value, and the upper bound expression's value. Next, the system can use computer algebra to determine whether the first expression's value is guaranteed to be between the lower bound expression's value and the upper bound expression's value. If the system determines that the first expression's value is not guaranteed to be between the lower bound expression's value and the upper bound expression's value, the system can add bounds-checking instructions to the one or more instructions.

Aspects of the invention relate generally to validating array bounds in an API emulator. More specifically, an OpenGL (or OpenGL ES) emulator may examine each array accessed by a 3D graphic program. If the program requests information outside of an array, the emulator may return an error when the graphic is drawn. However, when the user (here, a programmer) queries the value of the array, the correct value (or the value provided by the programmer) may be returned. In another example, the emulator may examine index buffers which contain the indices of the elements on the other arrays to access. If the program requests a value which is not within the range, the emulator may return an error when the graphic is drawn. Again, when the programmer queries the value of the array, the correct value (or the value provided by the programmer) may be returned.

One embodiment of the present invention sets forth a technique for performing a parallel scan operation with high computational efficiency in a single-instruction multiple-data (SIMD) environment. Each participating thread initially writes an extended region of a data array to initialize the region with an identity value. For example, a value of zero is used as the identity value for addition. The initialized region of the data array includes an initialized entry for every possible out of bounds index that may be computed in the normal course of the parallel scan operation. During the parallel scan operation each thread computes data array indices according to any technically appropriate technique. When a participating thread computes an index that would conventionally be out of bounds, the thread is able to retrieve an identity value from the initialized region of the data array rather than perform a bounds check that returns the identity value.