I wrote: > rather, one first has to use the corresponding modular > output to correct the bottom log2(q)/2 bits of the > floating output
If one has an approximate floating output and the same number modulo q (exactly) in hand, the one can obviously use the latter to correct up to the log2(q) least- significant bits of the former, i.e. there should be no divide by 2 in there. What I intended to say was that this allows one to use up to log2(q)/2 more bits per INPUT to the convolution (since outputs scale quadratically with input word size). For example, if one does the modular transform modulo the Mersenne prime M61, then floating outputs may be in error by as much as 2^60 (we lose one bit since floating outputs are signed) and still be exactly reconstructed, and this allows us to use roughly 30 more bits per input word. -Ernst _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
