hot spot

Region of the Earth's upper mantle that upwells to melt through the crust to form a volcanic feature. Most volcanoes that cannot be ascribed either to a subduction zone or to seafloor spreading at midocean ridges are attributed to hot spots. The 5% of known world volcanoes not closely related to such plate margins (see plate tectonics) are regarded as hot-spot volcanoes. Hawaiian volcanoes are the best examples of this type, occurring near the centre of the northern portion of the Pacific Plate. A chain of extinct volcanoes or volcanic islands (and seamounts), such as the Hawaiian chain, can form over millions of years where a lithospheric plate moves over a hot spot. The active volcanoes all lie at one end of the chain or ridge, and the ages of the islands or the ridge increase with their distance from those sites of volcanic activity.

hot spot

See hotspot.

hot spot

1. an area of potential violence or political unrest

a. any local area of high temperature in a part of an engine, etc.

b. part of the inlet manifold of a paraffin engine that is heated by exhaust gases to vaporize the fuel

3. Computing a company that provides wireless access to the internet for users of portable computers or the places from which the internet can be accessed in this manner

4. Med

a. a small area on the surface of or within a body with an exceptionally high concentration of radioactivity or of some chemical or mineral considered harmful

b. a similar area that generates an abnormal amount of heat, as revealed by thermography

5. Genetics a part of a chromosome that has a tendency for mutation or recombination

1.		hot spot - (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 optimisation 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.		hot spot - 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.		hot spot - A screen region that is sensitive to mouse clicks, which trigger some action. Hypertext help screens are an example, in which a hot spot exists in the vicinity of any word for which additional material is available.
4.		hot spot - 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.		hot spot - More generally, any place in a hardware design that turns into a performance bottleneck due to resource contention.