Use 1./n instead of 1/n. If n is an integer, 1/n equals 0. Matthieu
2008/9/9 Hanni Ali <[EMAIL PROTECTED]>: > Hi Matthieu, > > Interesting example thanks. I can't however seem to get anything other than > zero for the 100,000 to 1 sum. > > Cheers, > > Hanni > > 2008/9/9 Matthieu Brucher <[EMAIL PROTECTED]> >> >> > I now have a distinct dislike of float values (it'll probably wear off >> > over >> > time), how can the sum of 100,000 numbers be anything other than the sum >> > of >> > those numbers. I know the reasoning, as highlighted by the couple of >> > other >> > e-mails we have had, but I feel the default should probably lean towards >> > accuracy than speed. 2.0+2.0=4.0 and 2.0+2.0.....=200,000.0 not >> > 2array.sum() >> > != 200,000... >> >> In that case, we should not use doubles, but long double or even >> better, the real numbers themselves. Which would mean that >> computations would be very very very slow. >> Numpy leans somehow towards accuracy. If you want more accuracy >> (because even with double, you can hit the limit very fast), use >> another type. >> >> You said : >> how can the sum of 100,000 numbers be anything other than the sum of >> > those numbers >> >> This will always be a problem. With doubles, try to sum 1/n >> (1...100000), you'll be surprized. And then do sum 1/n (100000...1) >> with float values, and here the result should be better than when >> using doubles. Numerical issues in scientific computing are tricky. >> There is no single answer, it depends on your problem. >> >> Matthieu >> -- >> French PhD student >> Information System Engineer >> Website: http://matthieu-brucher.developpez.com/ >> Blogs: http://matt.eifelle.com and http://blog.developpez.com/?blog=92 >> LinkedIn: http://www.linkedin.com/in/matthieubrucher >> _______________________________________________ >> Numpy-discussion mailing list >> Numpy-discussion@scipy.org >> http://projects.scipy.org/mailman/listinfo/numpy-discussion > > > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion > > -- French PhD student Information System Engineer Website: http://matthieu-brucher.developpez.com/ Blogs: http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn: http://www.linkedin.com/in/matthieubrucher _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
