reduce()

template<Rank rank>

void syten::Tensor< rank >::reduce	(	EliminateZeros const	ezeros = EliminateZeros::Yes,
		bool const	add_cgc = false,
		bool const	no_para = false,
		bool const	no_zero_check_dense = false
	)

Reduce the number of blocks in the tensor by adding parallel blocks together.

Discards zero-blocks (i.e. blocks where norm(reduced) or norm(cgc) is smaller than SYTEN_ZNORM_THRESHOLD).

When building a tensor from many blocks, first push_back() all blocks and then call reduce() to minimise the overhead from comparisons.

Parameters

ezeros	if EliminateZeros::Yes, small tensors arising from large tensors will be removed
add_cgc	if true, CGC spaces will be added together if the dense spaces are parallel
no_para	if true, tensor-level parallelisation will be disabled
no_zero_check_dense	if true, assumes that dense tensors are never zero unless isZero is set on the block (true e.g. for products)

Finally, in every bin, check all blocks left over. If they are sufficiently large, move them into *this, otherwise drop them.

References std::begin(), syten::checkedAddParallel(), syten::clear(), syten::isZero(), syten::STensorImpl::log2(), std::move(), syten::pow(), syten::sqrt(), SYTEN_ASSERT, SYTEN_WARN_MSG, SYTEN_ZNORM_THRESHOLD_SQD, syten::tensorSortBuckets(), and syten::underThreshold().

Referenced by syten::addScaled(), syten::Deparallelise::cols(), syten::Delinearise::cols(), syten::exponentialTensorGen(), syten::exponentialTensorSym(), syten::MPS::Lat::U1U1::genFermiBoseLattice(), syten::MPS::Lat::SU2Fermion::genFermiHubbardSU2(), syten::MPS::ChemHelper::genMPO(), syten::T3N::ChemHelper::genMPO(), syten::MPS::Lat::genParity(), syten::MPS::Lat::genSU2Parity(), syten::MPS::left_complement(), syten::IPEPS::ATwoOp::operator+=(), syten::operator+=(), syten::operator-=(), syten::project(), syten::MPS::right_complement(), syten::Deparallelise::rows(), syten::SVD::svd(), syten::MPS::ChemHelper::tensorElem(), and syten::T3N::ChemHelper::tensorElem().

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