On Thu, 30 May 2013 12:07:40 +0300, Jussi Piitulainen wrote: > I suppose this depends on the complexity of the process and the amount > of data that produced the numbers of interest. Many individual > floating point operations are required to be within an ulp or two of > the mathematically correct result, I think, and the rounding error > when parsing a written representation of a number should be similar.
Elementary operations (+, -, *, /, %, sqrt) are supposed to be within +/- 0.5 ULP (for round-to-nearest), i.e. the actual result should be the closest representable value to the exact result. Transcendental functions should ideally be within +/- 1 ULP, i.e. the actual result should be one of the two closest representable values to the exact result. Determining the closest value isn't always feasible due to the "table-maker's dilemma", i.e. the fact that regardless of the number of digits used for intermediate results, the upper and lower bounds can remain on opposite sides of the dividing line. -- http://mail.python.org/mailman/listinfo/python-list
