On Sep 22, 2009, at 4:48 PM, Aubrey Jaffer wrote: > My solution was to limit the number of bits in a bignum, in SCM's > case 16000. Why this limit? Bignum operations have widely varying > asymptotic time requirements. SCM's multiplication is O(N^2). So > repeated doubling of a bignum value can quickly generate numbers > which would outlast anyone's patience to multiply. To the extent > possible, I want SCM's primitive operations to take bounded time and > space.
Maybe this is a counterpoint to the idea that it's possible to usefully implement bignums in pure Scheme. Of the implementations I tested with homegrown bignum implementations (in C), most handle multiplication of bignums up to 2^20 = 1048576 bits without too much trouble. GMP-based implementations will of course handle much larger numbers. > 1600 bits is adequate to do any cryptographic calculation for > the next several years. I'm assuming that this was a typo, and you meant 16000 again. -- Brian Mastenbrook [email protected] http://brian.mastenbrook.net/ _______________________________________________ r6rs-discuss mailing list [email protected] http://lists.r6rs.org/cgi-bin/mailman/listinfo/r6rs-discuss
