pytc.solver.isdf_xtc_ccsd

Factorized ISDF xTC-CCSD: RCCSD dispatch + factor-direct VVVV–T2 kernels.

The RCCSD class inherits the CCSD machinery of pytc.solver.jax_xtc_ccsd and replaces only the VVVV–T2 leg through that module’s instance hook. The rest of this module is the factor-direct contraction machinery it dispatches to. Full X stays on its host/HDF5 backing and is streamed one rank panel at a time (three residency tiers: device lift / host-resident / store stream). Opt-in rank-M X instead keeps its separated U/Z orbital factors through the T2 contraction. Neither path materializes a virtual four-index tile.

The raw ERI-like tile order in PyTC is (a, c, b, d); the public functions contract that tile directly with a dense RCCSD t2 in (i, j, c, d) order, without creating a (v, v, v, v) tile.

Classes

CompiledXLAMemory	Backend-specific buffer accounting reported by a JAX executable.
FactorDirectProfile	One steady-state contraction measurement.
RCCSD	JAX RCCSD whose default on-the-fly VVVV path is factorized.
_TuckerXFactors	Virtual-orbital Tucker factors for the factor-direct X branches.

Functions

_assemble_terms
_cgroup_memory_available_bytes	Available bytes under the most restrictive enclosing cgroup limit, or None.
_compiled_k12_memory	Compile the exact three-component K1/K2 branch for its XLA accounting.
_compiled_memory_from_executable	Return stable integer fields from JAX's executable memory analysis.
_compiled_partial_x_memory
_contract_full_thc_t2_impl	JIT implementation of the blocked full-THC VVVV--T2 contraction.
_contract_partial_x
_contract_tucker_x
_contract_x_t2_pipelined
_dtype_itemsize
_measure_free_device_bytes	Measured free bytes on the first local device, or None when unmeasurable.
_measure_free_host_bytes	Measured available host RAM in bytes, capped by any cgroup limit.
_pipelined_x_panel_size	Rank width of one pipelined X panel, a multiple of rank_panel_size.
_profile_call	Compile once, then record one synchronized steady-state wall time.
_read_x_rank_panel	Read one X rank panel from any backing (ndarray view or HDF5 dataset).
_read_x_rank_panel_major	Rank-major twin of _read_x_rank_panel(), returning rank-leading (panel_size, nvir, nvir) panels -- already the layout the panel kernels consume, and one CONTIGUOUS disk read per panel instead of ~nmo^2 strided chunks.
_stream_partial_x	Host-loop rank-panel streaming shared by the left and right X terms.
_stream_partial_x_pipelined	Working-set X panel loop with double-buffered async prefetch.
_validate_full_thc
_validate_t2
_validate_term_factors
_validate_tucker_x	Validate X[p,q,m] = U[p,a] Z[a,b,m] U[q,b] factors.
_validate_x
_validate_x_factors
_validate_x_stream
_x_backing_layout	Detect an X backing's axis layout: "innermost" or "rank_major".
_x_backing_panel_source	Panel source that reads straight from the X backing (tier 3).
_x_host_panel_source	Panel source that slices a host-resident X (tier 2).
compiled_full_thc_memory	Return XLA accounting for the compiled full-THC branch executable.
compiled_partial_x_left_memory	Return XLA accounting for P[a,m] P[c,m] X[b,d,m].
compiled_partial_x_right_memory	Return XLA accounting for X[a,c,m] P[b,m] P[d,m].
contract_full_thc_pair_swapped_t2	Contract V[b,d,a,c] for a full-THC V[a,c,b,d] term.
contract_full_thc_t2	Contract a full-THC (a,c,b,d) term with a dense RCCSD t2.
contract_terms_t2	Return each exact-current-ISDF VVVV--T2 branch and final residual.
contract_terms_t2_auto	Three-tier X path, selected on measured free memory.
contract_terms_t2_tucker	Factor-direct VVVV--T2 terms with rank-M Tucker X.
contract_terms_t2_xstream	Factor-direct terms with X streamed panel-wise from its backing.
contract_tucker_x_left_t2	Factor-direct left X term; neither dense X nor a V⁴ tile is formed.
contract_tucker_x_right_t2	Factor-direct pair X term; neither dense X nor a V⁴ tile is formed.
contract_x_left_t2	Contract P[a,m] P[c,m] X[b,d,m] without a V^4 tile.
contract_x_left_t2_pipelined	Pipelined P[a,m] P[c,m] X[b,d,m]: working-set panels, prefetched.
contract_x_left_t2_streamed	Streamed P[a,m] P[c,m] X[b,d,m]: one X rank panel on device at a time.
contract_x_right_t2	Contract X[a,c,m] P[b,m] P[d,m] without a V^4 tile.
contract_x_right_t2_pipelined	Pipelined X[a,c,m] P[b,m] P[d,m]: working-set panels, prefetched.
contract_x_right_t2_streamed	Streamed X[a,c,m] P[b,m] P[d,m]: one X rank panel on device at a time.
full_thc_schedule_intermediate_estimate_bytes	Estimate only the named live algebraic panels for a full-THC branch.
partial_x_schedule_intermediate_estimate_bytes	Estimate only the named live algebraic panels for an X branch.
profile_isdf_factor_direct_terms_t2	Measure every branch and return the exact factor-direct terms.