vesin_c Module

This is a Fortran interface to the C-API of vesin, from the header vesin.h.


Uses


Enumerations

enum, bind(c)

Enumerators

enumerator:: VesinUnknownDevice = 0

Unknown device, used for default initialization and to indicate no allocated data.
enumerator:: VesinCPU = 1

CPU device
enumerator:: VesinCUDA = 2

CPU device

Description

Device type on which the data can be

enum, bind(c)

Enumerators

enumerator:: VesinAutoAlgorithm = 0

Automatically select algorithm based on system size
enumerator:: VesinBruteForce = 1

Brute-force O(n^2) algorithm with minimum image convention
enumerator:: VesinCellList = 2

Cell list algorithm with O(n) scaling

Description

Algorithm to use for neighbor list construction


Interfaces

interface

Compute a neighbor list.

The data is returned in a VesinNeighborList. For an initial call, the VesinNeighborList should be default-initalized. The VesinNeighborList can be re-used across calls to this functions to re-use memory allocations, and once it is no longer needed, users should call vesin_free to release the corresponding memory.

  • public function vesin_neighbors(points, n_points, box, periodic, device, options, neighbors, error_message) result(status) bind(c, name="vesin_neighbors")

    Arguments

    Type IntentOptional Attributes Name
    real(kind=c_double), intent(in) :: points(3,n_points)

    Positions of all points in the system;
    integer(kind=c_size_t), value :: n_points

    Number of elements in the points array
    real(kind=c_double), intent(in) :: box(3,3)

    Bounding box for the system. If the system is non-periodic, this is ignored. This should contain the three vectors of the bounding box, one vector per column of the matrix.
    logical(kind=c_bool) :: periodic(3)

    Is the system using periodic boundary conditions? This should be an array of three booleans, one for each dimension.
    type(VesinDevice), value :: device

    Device where the points and box data is allocated.
    type(VesinOptions), value :: options

    Options for the calculation
    type(VesinNeighborList) :: neighbors

    A type(VesinNeighborList) instance, that will be used to store the computed list of neighbors.
    type(c_ptr), intent(in) :: error_message

    A type(c_ptr) to a null-terminated char* containing the error message of this function if any.

    Return Value integer(kind=c_int)

    Non-zero integer upon error; zero otherwise.

interface

Free all allocated memory inside a VesinNeighborList, according to it's device.

  • public subroutine vesin_free(neighbors) bind(C, name="vesin_free")

    Arguments

    Type IntentOptional Attributes Name
    type(VesinNeighborList) :: neighbors

Derived Types

type, public, bind(c) ::  VesinDevice

Device on which data can be allocated

Components

Type Visibility Attributes Name Initial
integer(kind=c_int), public :: type = VesinUnknownDevice

Device type (VesinUnknownDevice, VesinCPU, etc.)
integer(kind=c_int), public :: device_id = 0

Device index (0 for CPU, GPU index for CUDA)

type, public, bind(c) ::  VesinOptions

Used for storing Vesin options.

Components

Type Visibility Attributes Name Initial
real(kind=c_double), public :: cutoff = 0.0_c_double

Spherical cutoff, only pairs below this cutoff will be included
logical(kind=c_bool), public :: full

Should the returned neighbor list be a full list (include both i -> j and j -> i pairs) or a half list (include only i -> j)?
logical(kind=c_bool), public :: sorted = .false.

Should the neighbor list be sorted? If yes, the returned pairs will be sorted using lexicographic order.
integer(kind=c_int), public :: algorithm = VesinAutoAlgorithm

Which algorithm to use for the calculation
logical(kind=c_bool), public :: return_shifts = .false.

Should the returned VesinNeighborList contain shifts?
logical(kind=c_bool), public :: return_distances = .false.

Should the returned VesinNeighborList contain distances?
logical(kind=c_bool), public :: return_vectors = .false.

Should the returned VesinNeighborList contain vector?

type, public, bind(c) ::  VesinNeighborList

Used as return type from vesin_neighbors().

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Components

Type Visibility Attributes Name Initial
integer(kind=c_size_t), public :: length = 0_c_size_t

Number of pairs in this neighbor list
type(VesinDevice), public :: device

Device used for the data allocations
type(c_ptr), public :: pairs = c_null_ptr

Array of pairs (storing the indices of the first and second point in the pair), containing length elements.
type(c_ptr), public :: shifts = c_null_ptr

Array of box shifts, one for each pair. This is only set if options.return_pairs was true during the calculation.
type(c_ptr), public :: distances = c_null_ptr

Array of pair distance (i.e. distance between the two points), one for each pair. This is only set if options.return_distances was true during the calculation.
type(c_ptr), public :: vectors = c_null_ptr

Array of pair vector (i.e. vector between the two points), one for each pair. This is only set if options.return_vector was true during the calculation.
type(c_ptr), public :: opaque = c_null_ptr

Private pointer used to hold additional internal data