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apply_permutation_algebra for tensors from product rhs

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Jiri Pittner
2025-10-17 15:07:43 +02:00
parent 1dd3905d14
commit 08cdf7c971
3 changed files with 110 additions and 6 deletions
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9
tensor.h
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@@ -41,8 +41,7 @@
//@@@ will not be particularly efficient
//
//@@@permutation of individual indices - chech the indices in sym groups remain adjacent, calculate result's shape, loopover the result and permute using unwind_callback
//@@@todo - implement index names - flat vector of names, and contraction by named index list
//@@@todo grassmann product and support for RDM and cumulat stuff
//@@@todo!!! - implement index names - flat vector of names, and contraction by named index list
namespace LA {
@@ -217,8 +216,12 @@ public:
inline Tensor contractions( const INDEXLIST &il1, const Tensor &rhs2, const INDEXLIST &il2, T alpha=1, bool conjugate1=false, bool conjugate2=false) const {Tensor<T> r; r.addcontractions(*this,il1,rhs2,il2,alpha,0,true,conjugate1, conjugate2); return r; };
void apply_permutation_algebra(const Tensor &rhs, const PermutationAlgebra<int,T> &pa, bool inverse=false, T alpha=1, T beta=0); //general (not optimally efficient) symmetrizers, antisymmetrizers etc. acting on the flattened index list:
void apply_permutation_algebra(const NRVec<Tensor> &rhsvec, const PermutationAlgebra<int,T> &pa, bool inverse=false, T alpha=1, T beta=0); //avoids explicit outer product but not vectorized, rather inefficient
// this *=beta; for I over this: this(I) += alpha * sum_P c_P rhs(P(I))
// PermutationAlgebra can represent e.g. general_antisymmetrizer in Kucharski-Bartlett notation
// PermutationAlgebra can represent e.g. general_antisymmetrizer in Kucharski-Bartlett notation, or Grassmann products building RDM from cumulants
// Note that *this tensor can be e.g. antisymmetric while rhs is not and is being antisymmetrized by the PermutationAlgebra
// The efficiency is not optimal, even when avoiding the outer product, the calculation is done indexing element by element
// More efficient would be applying permutation algebra symbolically and efficiently computing term by term
void split_index_group(int group); //formal split of a non-symmetric index group WITHOUT the need for data reorganization
void merge_adjacent_index_groups(int groupfrom, int groupto); //formal merge of non-symmetric index groups WITHOUT the need for data reorganization
Tensor merge_index_groups(const NRVec<int> &groups) const;