GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t Derived Type

type, public, extends(DoubleExcitationGenerator_t) :: GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t

The GAS PCHB excitation generator for doubles using spin orbitals and doing full weighting. This means that first a hole is chosen via ( p( A | I J) |{A \notin D_i} ) !! then a second hole is chosen via ( p( B | I J A) | ).

This means it is guaranteed that only unoccupied sites are sampled.


Contents

Variables

Type-Bound Procedures

Source Code

GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t

Components

Type Visibility Attributes Name Initial
logical, public :: use_lookup = .false.

Use a lookup for the supergroup index in global_det_data
logical, public :: create_lookup = .false.

Create and manage! the supergroup index lookup in global_det_data.
class(ParticleSelector_t), private, allocatable :: particle_selector

The particle selector for I, J
type(AliasSampler_2D_t), private :: A_sampler

The sampler for the first hole A. It yields where IJ is a fused index I < J and i_sg is the supergroup.
type(AliasSampler_3D_t), private :: B_sampler

The sampler for the second hole B. It yields where IJ is a fused index I < J, A is the first hole and i_sg is the supergroup.
class(GASSpec_t), private, allocatable :: GAS_spec
type(SuperGroupIndexer_t), private, pointer :: indexer => null()
integer(kind=n_int), private :: last_possible_occupied

The last element of the ilut array has some elements which are not used, if the number of spinorbitals is not a multiple of bitsize_n_int. To correctly zero them this bitmask is 1 wherever a determinant could be occupied in the last element, and 0 otherwise.

Type-Bound Procedures

procedure, public :: init => GAS_doubles_PCHB_init

  • private subroutine GAS_doubles_PCHB_init(this, GAS_spec, use_lookup, create_lookup, PCHB_particle_selection)

    @brief Initialize the pchb excitation generator

    @details This does two things: 1. setup the lookup table for the mapping ab -> (a,b) 2. setup the alias table for picking ab given ij with probability ~

    Arguments

    Type IntentOptional Attributes Name
    class(GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t), intent(inout) :: this
    class(GASSpec_t), intent(in) :: GAS_spec
    logical, intent(in) :: use_lookup
    logical, intent(in) :: create_lookup
    type(PCHB_ParticleSelection_t), intent(in) :: PCHB_particle_selection

procedure, public :: finalize => GAS_doubles_PCHB_finalize

procedure, public :: gen_exc => GAS_doubles_PCHB_gen_exc

  • private subroutine GAS_doubles_PCHB_gen_exc(this, nI, ilutI, nJ, ilutJ, exFlag, ic, ex, tParity, pGen, hel, store, part_type)

    Given the initial determinant (both as nI and ilut), create a random double excitation using the hamiltonian matrix elements as weights

    Arguments

    Type IntentOptional Attributes Name
    class(GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t), intent(inout) :: this
    integer, intent(in) :: nI(nel)
    integer(kind=n_int), intent(in) :: ilutI(0:NIfTot)
    integer, intent(out) :: nJ(nel)
    integer(kind=n_int), intent(out) :: ilutJ(0:NifTot)
    integer, intent(in) :: exFlag
    integer, intent(out) :: ic
    integer, intent(out) :: ex(2,maxExcit)
    logical, intent(out) :: tParity
    real(kind=dp), intent(out) :: pGen
    real(kind=dp), intent(out) :: hel
    type(excit_gen_store_type), intent(inout), target :: store
    integer, intent(in), optional :: part_type

procedure, public :: get_pgen => GAS_doubles_PCHB_get_pgen

  • private function GAS_doubles_PCHB_get_pgen(this, nI, ilutI, ex, ic, ClassCount2, ClassCountUnocc2) result(pgen)

    @brief Calculate the probability of drawing a given double excitation ex

    @param[in] ex 2x2 excitation matrix

    @return pgen probability of generating this double with the pchb double excitgen

    Arguments

    Type IntentOptional Attributes Name
    class(GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t), intent(inout) :: this
    integer, intent(in) :: nI(nel)
    integer(kind=n_int), intent(in) :: ilutI(0:NIfTot)
    integer, intent(in) :: ex(2,maxExcit)
    integer, intent(in) :: ic
    integer, intent(in) :: ClassCount2(ScratchSize)
    integer, intent(in) :: ClassCountUnocc2(ScratchSize)

    Return Value real(kind=dp)

procedure, public :: gen_all_excits => GAS_doubles_PCHB_gen_all_excits

procedure, private, :: compute_samplers => GAS_doubles_PCHB_compute_samplers

procedure, private, :: get_unoccupied

  • private pure subroutine get_unoccupied(this, ilutI, ilut_unoccupied, unoccupied)

    Return a bitmask and enumeration of the unoccupied spin orbitals.

    Arguments

    Type IntentOptional Attributes Name
    class(GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t), intent(in) :: this
    integer(kind=n_int), intent(in) :: ilutI(0:nIfD)
    integer(kind=n_int), intent(out) :: ilut_unoccupied(0:nIfD)
    integer, intent(out) :: unoccupied(nBasis-nEl)

Source Code

    type, extends(DoubleExcitationGenerator_t) :: GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t
        !! The GAS PCHB excitation generator for doubles using spin orbitals
        !! and doing full weighting.
        !! This means that first a hole is chosen via \( p( A | I J) |_{A \notin D_i} )\
        !! then a second hole is chosen via \( p( B | I J A) |_{B \notin D_i} )\.
        !! This means it is guaranteed that only unoccupied sites are sampled.
        private
        logical, public :: use_lookup = .false.
            !! Use a lookup for the supergroup index in global_det_data
        logical, public :: create_lookup = .false.
            !! Create **and** manage! the supergroup index lookup in global_det_data.

        class(ParticleSelector_t), allocatable :: particle_selector
            !! The particle selector for I, J
        type(AliasSampler_2D_t) :: A_sampler
            !! The sampler for the first hole `A`.
            !! It yields \( p(A | IJ, i_{\text{sg}}) \)
            !! where IJ is a fused index I < J and `i_sg` is the supergroup.
        type(AliasSampler_3D_t) :: B_sampler
            !! The sampler for the second hole `B`.
            !! It yields \( p(B | A, IJ, i_{\text{sg}}) \)
            !! where IJ is a fused index I < J, A is the first hole and `i_sg` is the supergroup.
        class(GASSpec_t), allocatable :: GAS_spec
        type(SuperGroupIndexer_t), pointer :: indexer => null()
        integer(n_int), private :: last_possible_occupied
            !! The last element of the ilut array has some elements
            !! which are not used, if the number of spinorbitals is not a multiple of
            !! bitsize_n_int.
            !! To correctly zero them this bitmask is 1 wherever a determinant
            !! could be occupied in the last element, and 0 otherwise.
    contains
        private
        procedure, public :: init => GAS_doubles_PCHB_init
        procedure, public :: finalize => GAS_doubles_PCHB_finalize
        procedure, public :: gen_exc => GAS_doubles_PCHB_gen_exc
        procedure, public :: get_pgen => GAS_doubles_PCHB_get_pgen
        procedure, public :: gen_all_excits => GAS_doubles_PCHB_gen_all_excits

        procedure :: compute_samplers => GAS_doubles_PCHB_compute_samplers
        procedure :: get_unoccupied
    end type GAS_PCHB_DoublesSpinorbFullyWeightedExcGenerator_t