JargonFile/entries/hot spot.txt

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 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.