occ::qm::DFIntegrals Class Reference

Builds metric-folded density-fitting "B" tensors for correlated methods. More...

#include <df_integrals.h>

Public Member Functions
	DFIntegrals (IntegralEngineDF &df_engine, size_t memory_budget)
	memory_budget (bytes): if the dense (μν|P) store comfortably fits, it is built once and reused; otherwise B is built integral-direct per call.
size_t	nbf () const
size_t	naux () const
bool	uses_direct () const
	True if B is built integral-direct (no dense (μν|P) store).
Mat	build_b_tilde (Eigen::Ref< const Mat > C_left, Eigen::Ref< const Mat > C_right) const
	Build the metric-folded B tensor for the given MO coefficient blocks.

Detailed Description

Builds metric-folded density-fitting "B" tensors for correlated methods.

Given the 3-center AO integrals (μν|P) and the Coulomb metric V=(P|Q) owned by an IntegralEngineDF, build_b_tilde returns B̃ such that (ia|jb) = Σ_P B̃(ia,P) B̃(jb,P) i.e. the metric is folded in once (B̃ = B·L⁻ᵀ with V = L Lᵀ), so downstream code recovers MO integrals with a single GEMM and no per-pair metric solves.

Depending on the memory budget, the 3-center integrals are either stored densely once and reused (fast, O(nbf²·naux) memory) or streamed integral-direct per call (bounded memory, no dense store). Either way the returned B̃ is identical.

Constructor & Destructor Documentation

DFIntegrals()

occ::qm::DFIntegrals::DFIntegrals	(	IntegralEngineDF &	df_engine,
		size_t	memory_budget
	)

memory_budget (bytes): if the dense (μν|P) store comfortably fits, it is built once and reused; otherwise B is built integral-direct per call.

Member Function Documentation

build_b_tilde()

Mat occ::qm::DFIntegrals::build_b_tilde	(	Eigen::Ref< const Mat >	C_left,
		Eigen::Ref< const Mat >	C_right
	)		const

Build the metric-folded B tensor for the given MO coefficient blocks.

C_left: (nbf x nL) C_right: (nbf x nR) Returns (nL*nR x naux); the row for (i,a) is i*nR + a.

naux()

size_t occ::qm::DFIntegrals::naux ( ) const

inline

nbf()

size_t occ::qm::DFIntegrals::nbf ( ) const

inline

uses_direct()

bool occ::qm::DFIntegrals::uses_direct ( ) const

inline

True if B is built integral-direct (no dense (μν|P) store).

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The documentation for this class was generated from the following file:

• /home/runner/work/occ/occ/include/occ/qm/correlation/df_integrals.h