AMDG On 03/26/2012 10:55 PM, Thomas Mang wrote:

Hi,

Consider the mersenne_twister_engine<...> member function seeding a engine with an iterator range of seed values:

template<typename It> void mersenne_twister_engine<...>::seed(It &, It);

Is there some nice way to figure out how many seed values this function will need?

Create a ridiculously large vector and see how far the iterator is advanced.

I have used mt19937 and had to inspect the code to figure out it needs 624. I would find it very useful if this information is somewhere readily provided through some organized interface, e.g. a member function or a static class member stating that value. Same for other engine types.

It would be easier to use seed_seq, which is part of the C++11 library. The iterator interface was dropped for C++11.

BTW, I find it surprising that the first parameter is a reference to an iterator, and hence the input argument itself will be altered. Is that by design? If so what's the rationale? I think it's fairly odd behaviour, giving rise to unnecessary dangerousness and should become documented more clearly (big warning in bold flashing red letters etc. :) ).

This is intentional. The reason is so that the caller knows how many values were consumed. This is used by adaptors that take multiple engines, for example. In Christ, Steven Watanabe