Bosonic sites with itensor 2

Question

Hi guys,

I have a problem of syntax after I moved from Itensor 1 to Itensor 2. I had a piece of code which allows to create a set of sites, some of them spins the others bosons. I cannot construct anymore the bosons sites with a vector of 'IndexQN'. I have the feeling this is related to the new storage type of the library, but I am not sure :)

Thanks for your help!

inline void SpinBoson::
    constructSites()
    {
    std::vector<IndexQN> I;
    for(int j = 1; j <= N_; ++j)
    {
        if (std::binary_search(Is_.begin(),Is_.end(),j))
        {
                site_.at(j) = IQIndex(nameint("S=1/2 site=",j),
                                Index(nameint("Up for site",j),1,Site),QN(+1,0),
                                Index(nameint("Dn for site",j),1,Site),QN(-1,0));
        }
        else
        {
                for (int r = 0;r<d_;r++)
                {
                        std::string str = format("%d for site %d",r,j); 
                        I.push_back(IndexQN(Index(str,1,Site),QN(0,r)));
                }
                site_.at(j) = IQIndex(nameint("boson site=",j),I);
        }
    }
    }

Note, the error is

no matching constructor for initialization of
  'itensor::IQIndex'
        site_.at(j) = IQIndex(nameint("boson site=",j),I);
                      ^       ~~~~~~~~~~~~~~~~~~~~~~~~~~
itensor2/itensor/iqindex.h:55:5: note: candidate constructor not viable: no known conversion from
      'std::vector<IndexQN>' to 'storage &&' (aka 'vector<itensor::IndexQN> &&') for 2nd argument

Answer 1

Hi, thanks for the question.

At a glance, the line

site_.at(j) = IQIndex(nameint("boson site=",j),I);

seems to be what's causing the problem. I think all you need to do to fix it is change the line to

site_.at(j) = IQIndex(nameint("boson site=",j),std::move(I));

The 2.0 version of this constructor still accepts a vector but for efficiency reasons requires it to be "moved" into the IQIndex to avoid making a copy. Be aware that afterward the vector I will be empty.

Please give it a try and let me know if it works or not!

Answer 2

It seems to work. Thanks a lot!