pathological

1. [scientific computation] Used of a data set that is grossly

atypical of normal expected input, especially one that exposes

a weakness or bug in whatever algorithm one is using. An

algorithm that can be broken by pathological inputs may still

be useful if such inputs are very unlikely to occur in

practice.

2. When used of test input, implies that it was purposefully

engineered as a worst case. The implication in both senses is

that the data is spectacularly ill-conditioned or that someone

had to explicitly set out to break the algorithm in order to

come up with such a crazy example.

3. Also said of an unlikely collection of circumstances. "If

the network is down and comes up halfway through the execution

of that command by root, the system may just crash." "Yes,

but that's a pathological case." Often used to dismiss the

case from discussion, with the implication that the

consequences are acceptable, since they will happen so

infrequently (if at all) that it doesn't seem worth going to

the extra trouble to handle that case (see sense 1).

[Jargon File]