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hot spot: n. 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
hotlinks). 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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