Torbjorn Granlund <t...@gmplib.org> writes: > I would like to avoid fp hardware in the portable parts of GMP.
I guess this means: Avoid using functions from libm, and avoid using floating point in critical loops. Right? There's a (non-critical) floating point operation in mpn_perfect_power_p involving some logarithm table. > Looping around umul_ppmm, keeping the msb = 1 should give a few > correct bits. > > The error will depend on the limb size and on n. For the ASL patch > (artificially small limbs) we might not be able to make this work. It would make some sense to introduce an mpn_powhi, which computes an approximation of the high n (normalized?) limbs. Would be useful also for mpfr, I guess. It would either have a documented maximum error, or it could return an error bound (I imagine the error bound could be slithly different for plain binary exponentiation and window based exponentiation). > I need to look into the present algorithn to get completely convinced, > though. I was under the impression that it in practice rejected bad n > values after a b-adic run at few-word "precision". If I understand this correctly, most bad n ought to be rejected as soon as the precision is xn+1 or larger. Regards, /Niels -- Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26. Internet email is subject to wholesale government surveillance. _______________________________________________ gmp-devel mailing list gmp-devel@gmplib.org http://gmplib.org/mailman/listinfo/gmp-devel
