Dear Frieder, On Wed, 19 Jan 2005, Frieder Kalisch wrote:
here is a very odd performance behaviour of ginac/series.
Okay, I had a quick look at this. There are two questions that I am asking myself now: (1) How should .series() perform its calculation? (2) What should the result be like? Ad (1): I think series expansion should most of the time not be done by repeated differentiation. What if some large addition appears as a subexpression? The chain rule together with expansion of the derivatives (in the sense of .expand()) will cause expression explosion and happyness is not going to occur. Ad (2): I think that the expansion coefficients should be in expandend form (again in the sense of .expand()). If the main developpers agree on this, then you have just located a bug. The coefficients of the result of your example look more than a bit unexpanded.... Best wishes, Chris