hot spot

1. [primarily used by C/Unix programmers, but spreading] It is received wisdom that in most programs, less than 10% of the code eats 90% of the execution time; if one were to graph instruction visits versus code addresses, one would typically see a few huge spikes amidst a lot of low-level noise. Such spikes are called hot spots and are good candidates for heavy optimization or {hand-hacking}. The term is especially used of tight loops and recursions in the code's central algorithm, as opposed to (say) initial set-up costs or large but infrequent I/O operations. See {tune}, {hand-hacking}.
2. The active location of a cursor on a bit-map display. "Put the mouse's hot spot on the `ON' widget and click the left button."
3. A screen region that is sensitive to mouse gestures, which trigger some action. World Wide Web pages now provide the {canonical} examples; WWW browsers present hypertext links as hot spots which, when clicked on, point the browser at another document (these are specifically called {hotlink}s).
4. In a massively parallel computer with shared memory, the one location that all 10,000 processors are trying to read or write at once (perhaps because they are all doing a {busy-wait} on the same lock).
5. More generally, any place in a hardware design that turns into a performance bottleneck due to resource contention.

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