id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
62,Rational sum not optimal for overflows,nobody,Jonathan Turkanis,"{{{
The sum of n1/d1 + n2/d2 should be calculated as:

L*((n1'*d2'+n2'*d1')/m)
-----------------------
     (k/m)*d1'*d2'

where

m = gcd(k, n1'*d2'+n2'*d1')
k = gcd(d1, d2)
L = gcd(n1, n2)

k*d1'=d1
k*d2'=d2
L*n1'=n1
L*n2'=n2

This way overflows are avoided while calculatins the 
resulting numerator (since division by m is performed 
before multiplication by L).

Manuel.Sequeira@iscte.pt
}}}",Bugs,closed,,None,None,,Rejected,,