Single Element ITensor

A single element ITensor is an ITensor constructed using the setElt function. It has exactly one non-zero element, which can be any element.

(Currently this type of ITensor uses dense storage but this is subject to change in the future.)

setElt is defined in "itensor/itensor_interface.h" and "itensor/itensor_interface_impl.h".

Synopsis

auto i = Index(4);
auto j = Index(3);

auto T = randomITensor(i,j);

auto S = setElt(i=2);

//Multiplying by S in this case will "quench"
//the i Index of T to its second value:
T *= S;

Specification

setElt(IndexVal iv1, IndexVal iv2, ...) -> ITensor

Given one or more IndexVals, return an ITensor with all elements set to zero except the element corresponding to the IndexVals which is set to 1.0.

 auto s = Index(3);
 auto l = Index(10);

 auto T = setElt(s=2,l=4);

 Print(elt(T,s=1,l=1)); //prints: 0.0
 Print(elt(T,s=2,l=1)); //prints: 0.0
 //...
 Print(elt(T,s=2,l=4)); //prints: 1.0

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