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, bum, 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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