Lookup Table

In computer science, a lookup table is a data structure, usually an array or associative array, often used to replace a runtime computation with a simpler array indexing operation. The savings in terms of processing time can be significant, since retrieving a value from memory is often faster than undergoing an 'expensive' computation or input/output operation. The tables may be precalculated and stored in static program storage, calculated (or "pre-fetched") as part of a programs initialization phase (memoization), or even stored in hardware in application-specific platforms. Lookup tables are also used extensively to validate input values by matching against a list of valid (or invalid) items in an array and, in some programming languages, may include pointer functions (or offsets to labels) to process the matching input.

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Other articles related to "lookup table, tables, lookup tables, table":

Other Usage of Lookup Tables - Hardware LUTs
... In digital logic, an n-bit lookup table can be implemented with a multiplexer whose select lines are the inputs of the LUT and whose inputs are constants ... n-bit LUT can encode any n-input Boolean function by modeling such functions as truth tables ...
Examples - Lookup Tables in Image Processing
... In data analysis applications, such as image processing, a lookup table (LUT) is used to transform the input data into a more desirable output format ... A classic example of reducing run-time computations using lookup tables is to obtain the result of a trigonometry calculation, such as the sine of a value ... the sine of a number of values, for example for each whole number of degrees (The table can be defined as static variables at compile time, reducing repeated run time costs) ...
How FXT1 Texture Compression Works, As Set Out in The Original White Paper
... the primary colors for this texel block and its associated four color lookup table ... A 2-bit index is used to determine which color from the lookup table will be used for each texel in the 4x4 block ... index is used to determine which color from the 8-entry lookup table will be used for each texel in the 4x8 block ...
Map-based Controller
... based on values derived from a pre-defined lookup table ... one or more sensors and are used to index the output values in the lookup table ... By effectively placing the transfer function as discrete entries within a lookup table, engineers free to modify smaller sections or update the whole list of entries as required ...
Framebuffer - Color Palette
... The solution to this problem was to add a lookup table to the framebuffers ... The lookup table served as a palette that contained data to define a limited number (such as 256) of different colors ... which of the colors in the palette was for the current pixel, and the data stored in the lookup table (sometimes called the "LUT") went to three ...

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