Quite Upset with NIntegrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg54142] Quite Upset with NIntegrate*From*: ituran at bohr.concordia.ca (I. Turan)*Date*: Fri, 11 Feb 2005 03:34:40 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi: I have been trying to evaluate a 4-dimensional integral by using NIntegrate with Mathematica 4 w2k. The integrand and even the integration limits are quite complicated (depending on int. variables). The length of the integrand is around 2000 lines in the FortranForm. If I don't play with any options of NIntegrate, It takes one day to get one data point and gives very unreasonably weird values. By setting, however, MaxPoints something like 100000 it is possible to get faster results but still it seems that Mathematica couldn't handle it. When I draw a figure from these data points, it appears very very spiky such that it is even not possible to fit the curve. However, it is supposed to be very smooth. Should I accept that Mathematica can not handle such a numerical integration or is there a way to make Nintegrate working better? Thanks a lot, Ismail

**Follow-Ups**:**Re: Quite Upset with NIntegrate***From:*Chris Chiasson <chris.chiasson@gmail.com>

**Re: Quite Upset with NIntegrate***From:*yehuda ben-shimol <bsyehuda@gmail.com>