- Move Semantics:
It is not clear, and not documented!
That's because it's presently not used. The code is all there for it, but it's disabled because the future of Boost.Move was still up in the air when I wrote it.
To turn it on, define BOOST_XINT_USE_MOVE before including any XInt headers. [...]
boost::xint::integer a,b; a = 100; b = boost::move(a); // expect like swap(a,b) acts like a=b std::cout << a<<" " <<b << std::endl; // expect 0 100, get 100, 100
I haven't tried it, but that code should work the way you expect with the move code enabled.
Yes adding this define makes it work... So it would be good to have it documented :-) And this is really nice feature. Seems that integer is capable of handling all possible styles: copy, copy-on-write, move. Way to go! +1
This is the weakest point of this library, the performance of too many algorithms is very low [...]
A lot of that may be due to pass-by-value instead of const references, rather than the algorithms, which I've already corrected for the next release. I'll be testing that soon, maybe today, along with the CoW/move speeds.
Not so sure because I've tried with cow turned on and off and results were almost the same. AFAIK xint uses "naive" multiplication algorithm and probably some others. For me it seems like O(f(n)) issues. Because the ratio between GMP and Xint gets lower as numbers grow. I'd suggest to take a look on algorithms that GMP and other use and re-implement them.
John Bytheway introduced me to a new primality algorithm that I plan to add.
If you are talking about deterministic primality check (ASK)... Don't bother too much, nobody uses them in reality and they have O(scary) complexity. It is something like O(n^6) where n is number of digits... So don't bother. It is the last thing that users would actually need.
First problem that should be solved are actually algorithms complexities, I don't think it is something too hard. Reading few books and papers would guide a strightforward direction to the solution. [...]
I'll report on the speed changes from the alterations I've already made as soon as I have them. I don't want to check any code into Subversion until the review is over (the reviews should all be of the same code), but I can make the updated code available earlier if anyone wants it.
I'd suggest you to create a small set of benchmarks of xint vs GMP so you can see progress. Regards Artyom