add zkp-u256

[joleeee]

No description provided.

[joleeee]

the problem is that the type doesnt' implement Copy so we have to add explicit Clones everywhere

not sure if i could just add Copy as the repo (no longer?) compiles, it hasn't been updated in 1.5y for some reason...

[joleeee]

the perf on 3n+1 is quite good, but it's terrible for fib for some reason

test fib::ethereum::_u128_         ... bench:      12,085 ns/iter (+/- 60)
test fib::ethereum::_u256_         ... bench:      16,865 ns/iter (+/- 2,086)
test fib::ethereum::_u64_          ... bench:       2,023 ns/iter (+/- 7)
test fib::native::_u128_           ... bench:       2,052 ns/iter (+/- 7)
test fib::native::_u64_            ... bench:       2,026 ns/iter (+/- 5)
test fib::zkp::_u256_              ... bench:      87,357 ns/iter (+/- 381)
test three_n_one::ethereum::_u128_ ... bench:       4,308 ns/iter (+/- 261)
test three_n_one::ethereum::_u256_ ... bench:       6,193 ns/iter (+/- 47)
test three_n_one::ethereum::_u64_  ... bench:         765 ns/iter (+/- 6)
test three_n_one::native::_u128_   ... bench:         141 ns/iter (+/- 0)
test three_n_one::native::_u64_    ... bench:          69 ns/iter (+/- 0)
test three_n_one::zkp::_u256_      ... bench:       4,318 ns/iter (+/- 36)